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258 Background: Tumors harboring 2 or more PIK3CA Short variants (SV) (“Multi-hit”) have been described in breast cancer as linked to enhanced clinical outcome from anti-PIK3CA targeted therapies including alpelisib and investigational agents in clinical trials. The landscape and clinical implications of multi-hit PIK3CA alterations in other tumors, including in CAPC, are underexplored. Methods: 19,978 CAPC samples underwent hybrid capture based comprehensive genomic profiling (CGP) to evaluate all classes of GA and determine tumor mutational burden (TMB), microsatellite instability (MSI), genomic ancestry, signature and loss of heterozygosity (gLOH). Tumor cell PD-L1 expression was determined by IHC (Dako 22C3). Results: 18,741 (93.8%) CAPC were PIK3CA wild type (WT), 1,155 (5.8%) featured a single PIK3CA SV and 82 (0.4%) featured multi-hit PIK3CA SVs. The median ages of CAPC patients with single hit (69.1 yrs) or multi-hit (68.7 yrs) PIK3CA SV were older than the PIK3CA WT (67.6 yrs) CAPC (p

564 Background: CDH1 mutated UBCs are characterized by plasmacytoid histology and are associated with an aggressive clinical course at the time of diagnosis. Methods: Cohort 1: 6,676 clinically advanced UBC patients (pts) underwent comprehensive genomic profiling (CGP) to evaluate all classes of genomic alterations (GA), microsatellite instability (MSI), tumor mutational burden (TMB), and genomic loss of heterozygosity (gLOH, high ≥16%). Predominant genetic ancestry was determined using a SNP-based approach and classified as one of the 5 categories: African (AFR), European (EUR), Central and South American (AMR), South Asian (SAS), or East Asian (EAS). Cohort 2: 586 UBC pts underwent a RWCOS using the nationwide (US-based) de-identified Flatiron Health-Foundation Medicine urothelial clinico-genomic database (FH-FMI CGDB). The de-identified data originated from approximately 280 US cancer clinics (~800 sites of care) Jan 2011-Apr 2022. Differences in real-world progression-free survival (rwPFS) and overall survival (rwOS) were evaluated by Cox proportional hazard models. Results: Cohort 1: 217 (3.3%) of UBC had a CDH1 short variant (SV) mutation with 65.2% featuring plasmacytoid histology. When compared with CDH1 wild-type (WT) UBC, the CDH1-mutated UBC had similar age, gender, and genetic ancestry. The CDH1-mutated UBC featured a higher frequency of MSI (2.7% vs 0.8%; p=.002), mean TMB (14.8 vs 9.9 mut/Mb p

566 Background: Given the recent approval in lung cancer for the first anti-HER2 targeted therapy directed against activating kinase domain exon 20 ERBB2 insertion mutations, considerable interest has arisen in targeting additional locations in the ERBB2 gene in other tumor types. Methods: 5,485 UBC samples were sequenced using a hybrid capture-based comprehensive genomic profiling (CGP) assay to assess all classes of genomic alterations (GA), tumor mutational burden (TMB), microsatellite instability (MSI), genomic loss of heterozygosity (gLOH), trinucleotide signatures and predominant genetic ancestry. Statistical comparisons utilized the Bonferroni correction. Results: 548 (10.0%) of UBC featured ERBB2 gene amplification (amp) and 219 (4.0%) featured an ERBB2 ECD+ sequence mutation (74% S310F and 26% S310Y). ERBB2 ECD+ mutations and ERBB2 amplification were mutually exclusive. 16.4% of ERBB2 ECD+ UBC had more than one E RBB2 sequence mutation. Central pathology review of the 219 ERBB2 ECD+ UBC revealed that 63 (28.8%) featured a micropapillary histologic appearance (MPUC). ERBB2 ECD+ UBC featured more patients with European ancestry than both ERBB2 WT (90.9% vs 84.2%; p=.03) and ERBB2 amp (90.9% vs 83.2%; p=.04). ECD mut+ UBC also featured lower association with African ancestry than ERBB2 amp (2.7% vs 7.8%; p=.04) and lower frequency of gLOH > 16% (9.3% vs 19.1%; p=.04). MSI-High status was similar and rare in all 3 groups (range 0 to 0.9%). ERBB2 ECD+ UBC had a higher frequency of APOBEC signature than ERBB2 amp (82.9% vs 72.4%; p=.03). TMB > 10 mut/mb was higher in ERBB2 amp (49.2% vs 31.4%; p

4 Background: TMB has emerged as a major biomarker of efficacy in immune checkpoint inhibitor (ICPI) therapies in the neoadjuvant, adjuvant and metastatic disease setting in a wide variety of malignancies, but not in PSCC. Methods: 397 clinically advanced (local major recurrence and/or metastatic disease) PSCC underwent hybrid capture-based comprehensive genomic profiling (CGP) to evaluate all classes of genomic alterations (GA). Tumor mutational burden (TMB) was determined on up to 1.1 Mb of sequenced DNA and microsatellite instability (MSI) was determined on up to 114 loci. Trinucleotide mutation signatures were evaluated (Alexandrov, et al. 2013). Genome-wide loss of heterozygosity (gLOH) was determined using validated pipelines and excluding whole-arm and whole-chromosome events. TMB was categorized into three cohorts: 20 muts/Mb (very high). Tumor cell PD-L1 expression was determined by IHC (Dako 22C3) and defined as tumor proportion score (TPS) >1. The presence of HPV16/18 was determined by next generation sequencing (NGS). Statistical comparisons were corrected for multiple comparisons using the Bonferonni method. Results: There were 339 (85.4%) TMB low, 40 (10.1%) TMB 10-19 and 18 (4.5%) TMB very high PSCC cases in this study. The mean age of PSCC with very high TMB at 70.1 yrs was older than for TMB low at 63.4 yrs (p=.08). There were no significant differences in genomic ancestry among the 3 groups. The TMB 10-19 and TMB very high tended to feature an APOBEC genomic mutational signature more than the TMB low PSCC cases (74 and 76% vs 44%). MSI high status was absent in the TMB low PSCC, but was present in 7.5% of the TMB 10-19 and 11.8% of the TMB very high cases. gLOH levels above 16% were similar in all 3 groups and ranged from 6.2 to 9.4%. GA associated with differences in TMB status in the PSCC cases included higher PIK3CA GA in TMB 10-19 (40.0%) vs TMB low (18.3%; p=.035) and TMB very high (66.7%) vs TMB low (p=.0002). CDKN2A GA were higher in TMB low (45.7%) than in the combined TMB 10-19 + very high (25.9%; p=.049). GA in KMT2D were higher in the combined TMB 10-19 + very high (29.3%) than the TMB low PSCC (7.7%; p=0002). FGFR3 GA were similar in all 3 groups. PD-L1 expression was not significantly different among the 3 groups with TMB low (78.3%), TMB 10-19 (64.2%) and TMB very high (54.5%). HPV identification was more frequent as TMB increased: 28.3% for the TMB low, 50.0% for the TMB high and 58.8% for the TMB very high groups. Conclusions: The evaluation of PSCC by CGP based on TMB levels revels significant differences in biomarkers for the near 15% of cases that have TMB >10 muts/Mb. Further study of TMB as a biomarker in ICPI-based clinical trials for advanced PSCC appear warranted.

567 Background: UBC is the 10th most common cancer worldwide, with more than 550,00 new cases annually (WHO, International Agency for Research on Cancer, 2020). Rates vary by regions of the world, explained in part by the fact that different genetic ancestries demonstrate varying germline genetics, environmental exposures, and social risk factors. Methods: 8,728 UBC samples underwent hybrid capture-based comprehensive genomic profiling (CGP) to determine all classes of genomic alterations (GA), microsatellite instability (MSI) status, tumor mutational burden (TMB), and genomic trinucleotide signature. Predominant genetic ancestry was determined using a SNP-based approach using an algorithm trained on the 1000 Genomes data (Connelly et al. AACR 2018). Ancestry was classified as one of the five following categories: African (AFR), European (EUR), Central and South American (AMR), South Asian (SAS), or East Asian (EAS). Results: Of the cohort, 7,447 (85.3%) were EUR, 541 (6.2%) were AFR, 461 (5.3%) were of AMR, 74 (0.85%) were SAS, and 205 (2.3%) were EAS. Age, gender, genomic signature distributions, and MSI status (range 0.9%-1.5%) were similar in all cohorts. The frequency of TMB >10 mutations/Megabase was similar in all cohorts (range 30.7%-39.1%) as was the median TMB (6.3 mutations/Megabase for all). At 67.6%, TP53 was the most frequent GA in SAS cohort. When compared with the non-SAS cohort, TERT GA were lower in the SAS cohort (58.1% vs 72.6%; p=0.06) as were GA in FGFR3 (9.5% vs 18.5%, p=0.25). In the EAS cohort, at 59.0%, GA in TP53 were the most common. TERT mutations were significantly lower in EAS compared to the non-EAS cohort (54.1% vs 72.9%; p

5063 Background: NEPC is a high-grade aggressive form of prostate cancer. We queried whether RB1 mutation status would impact the genomic features of NEPC in RB1 mutated vs non-mutated cases. Methods: From a series of 13,496 cases of clinically advanced PC, we identified 415 cases (3.1%) with a diagnosis of small cell PC or NEPC as determined by the submitting physician. They were sequenced using a hybrid capture-based FDA-approved clinical genomic profiling (CGP) assay to detect all classes of genomic alterations (GA). Tumor mutational burden (TMB) was determined on 0.8 Mbp of sequenced DNA and microsatellite instability (MSI) was determined on 95 loci. PD-L1 expression was determined by IHC (Dako 22C3) with low tumor cell positive staining 1-49% and high staining ≥50% expression. Results: 253 (61%) of NEPC feature GA in RB1 (RB1 mut+). This contrasts with a 5.8% frequency of RB1 GA in the non-NEPC (P

e16535 Background: Immunohistochemistry (IHC) to determine PD-L1 expression level has been used as a biomarker to predict immune checkpoint inhibitors response in UCB. We hypothesized that the GA profiles would differ between UCB featuring high vs negative PD-L1 expression. Methods: 102 cases of advanced UCB with known PD-L1 tumor cell expression underwent hybrid-capture based comprehensive genomic profiling to evaluate all classes of genomic alteration (GA). Tumor mutational burden (TMB) was determined on up to 1.1 Mbp of sequenced DNA and microsatellite instability (MSI) was determined on 114 loci. Tumor cell (TC) PD-L1 expression was determined by IHC (Dako 22C3). Only PD-L1 high (H) (≥50% TC expression) and negative (N) (0% TC expression) cases were included in this study. Results: Overall, only 2 (8.3%) of the 24 PD-L1H UCB featured CD274 ( PD-L1) amplification (mean 19 copies) and none of 78 PD-L1N had CD274 amplification (P = .05). The gender, age and GA per tumor frequencies were similar in the groups. When compared with the PD-L1H UBC cases, FGFR3 GA were significantly more frequent in the UBC PD-L1N cases (p = .02). Currently “untargetable” GA that were more frequent in the PD-L1H UBC, but did not reach significance, included TP53, TERT and RB1. MTAP loss, a potential target for PRMT5 and MTA2 inhibitors, were 3X more frequent in the PD-L1N UBC. ERBB2 amplification and ERBB3 and PIK3CA short variant (SV) GA were more frequent in the PD-L1N UBC with differences not reaching significance. The mean gLOH scores were similar in both groups. Other ICPI-associated potential biomarkers, including MSI status, TMB level and GA in PBRM1, STK11 and MDM2 were not significantly different in the groups. For UCB cases where a mutational signature could be determined, 15/33 (45%) of PD-L1H and 34/112 (30%, p = 0.14) of PD-L1N UCB featured an APOBEC gene signature; 79% of PD-L1H and 83% of PD-L1N featured European ancestry (p = 0.61). Conclusions: PD-L1H and PD-L1N subtypes of UCB differ in their genomic profiles. PD-L1N UCB features greater frequencies of potentially “targetable” GA, including FGFR3, ERBB2, ERBB3 and PIK3CA. PD-L1 IHC may thus not only play a role in the selection of ICPI for advanced UCB but also in designing trials that may combine ICPI with targeted therapies.[Table: see text]

e17014 Background: Prostate Specific Antigen (PSA) testing can improve early prostate cancer detection. However, numerous factors can influence patients’ willingness and ability to undergo PSA testing. Methods: We performed a cross-sectional study investigating the impact of various degrees of ischemic heart disease (IHD) on PSA testing. We assessed 3,822 male respondents aged 55-75 from the 2018 year of the National Health Interview Survey (NHIS). Men were stratified according to the degree of IHD (none, history of angina pectoris (AP), history of myocardial infarction (MI), or history of neither, but with a diagnosis of IHD). Multivariable logistic regression analysis was used to assess the relationship between IHD and being tested for PSA, adjusting for known cofounders. Results: Multivariable logistic regression demonstrated that males with a history of IHD (no MI or AP) were more likely to have ever been PSA tested than males without IHD (p = 0.012, OR = 1.630, 95% CI 1.115-2.383), as seen in Table. Additionally, older age (p < 0.001), having a partner (vs. no partner p < 0.001), homosexual sexual orientation (vs. heterosexual orientation p = 0.007), and a history of cancer (vs. no history p < 0.001) all increased likelihood of being PSA tested. In contrast, Asian race (vs. White, p = 0.001), and being a current smoker (vs. no smoking history, p < 0.001) decreased the likelihood. Interestingly, males with a history of a symptomatic IHD (MI or AP) were not shown to be more likely to undergo PSA testing. Conclusions: Our results suggest that males with non-symptomatic IHD are more likely to be PSA tested. Males with symptomatic IHD do not seem to undergo more PSA screening, perhaps due to lower suggested life expectancy. Awareness of discrepancies in PSA testing in men with IHD should be raised. Table - Multivariable logistic regression analyses demonstrating relationships with likelihood of being PSA tested.[Table: see text]

4550 Background: FLCN is a tumor suppressor gene associated with cutaneous hair follicle development. FLCN germline mutations are linked to inherited chrRCC in the Birt-Hogg-Dube (BHD) syndrome. We queried whether clinically sporadic chrRCC featured FLCN mutations by comparing the genomic profiles of chrRCC with nonchrRCC. Methods: 109 chrRCC and 5,862 nonchrRCC underwent hybrid-capture based comprehensive genomic profiling (CGP) to evaluate all classes of genomic alterations (GA). Tumor mutational burden (TMB) was determined on up to 1.1 Mb of sequenced DNA and microsatellite instability (MSI) was determined on 114 loci. PD-L1 expression was determined by IHC (Dako 22C3). Results: Patients (pts) with chrRCC were more frequently female (37 [34%] vs. 1,817 [31%]) and younger than pts with nonchrRCC (median age 58 vs 62 years, p

e18558 Background: Research has shown that the COVID-19 pandemic has reduced access to cancer treatment and care for patients, especially for COVID-19 patients. Methods: We investigated the impact of COVID-19 testing on access to cancer care. A US based cross sectional study was conducted on 2,393 cancer patients using data from the 2020 National Health Interview Survey. Multivariable logistic regression was used to assess associations between COVID-19 testing and likelihood of receiving cancer treatment or other cancer care during the pandemic. Results: Patients who reported ever being tested for COVID were on average younger (66.9 vs 69.3, p

4568 Background: Urothelial bladder carcinomas (UBC) with genomic alterations (GA) in the Fibroblast Growth Factor Receptor ( FGFR) genes have been postulated to be less responsive to immune checkpoint inhibitors (ICI). Immune microenvironment of these tumors could be altered due to suppression of interferon signaling pathways. Here, we present comprehensive genomic profiling (CGP) of FGFR altered UBC to study the underlying immunogenomic mechanisms of response and resistance. Methods: 4,035 UBC underwent hybrid capture based CGP. Tumor mutational burden (TMB) was determined on up to 1.1 Mbp of sequenced DNA and microsatellite instability (MSI) was determined using 114 loci. Programmed death ligand (PD-L1) expression in tumor cells was assessed by IHC (Dako 22C3). Results: 894 (22%) of UBC featured FGFR GA ( FGFR1 3.7%; FGFR2 1.1%; FGFR3 17.4%). Gender and age distribution was similar in all groups. FGFR3 cases had lower GA/tumor and 14.7% GA were fusions. ERBB2 amplification was significantly higher in FGFR1/2 altered UBC compared with FGFR3 altered UBC. MTOR pathway GA were highest in FGFR3 altered UBC. FGFR3 altered UBC featured significantly higher frequencies of biomarkers predicting resistance to ICI including lower TMB, lower PD-L1 expression and higher frequencies of GA in MDM2. FGFR3 driven UBC also features significantly higher frequencies of CDKN2A/B loss and MTAP loss which have also recently been linked to IO drug resistance. Conclusions: UBC harboring FGFR GA have increased frequency of alterations that have been linked to ICI resistance. Further evaluation of FGFR-based biomarkers in UBC clinical trials focused on the assessment of the patient response to ICI appears warranted. [Table: see text]

21 Background: The term ‘financial toxicity’ or ‘hardship’ is used to describe the financial problems patients experience due to high out-of-pocket costs for their healthcare. Financial toxicity in the context of cancer treatment is an area of recent study due to the significant costs associated with these treatments, but little is known about the effect of financial toxicity on cancer prevention. We examined the effects of financial toxicity on the utilization of screening tests for prevalent cancers, including prostate and colon cancer, using a US nationally representative survey-based data source. We hypothesized that patients with more financial hardship would show an association with decreased prevalence of prostate and colon cancer screening. Methods: This cross-sectional survey-based US study included men and women aged 18+ from the National Health Interview Survey (NHIS) database from January – December 2018. A financial hardship score between 0 and 1 was formulated by summarizing the responses from ten financial toxicity questions including if in the past 12 months one was unable to afford prescription medication or healthcare; or if one had to skip or take less medicine to save money. A higher score was associated with a worse financial hardship score. The primary outcomes of the study were self-reported occurrence of PSA blood testing for prostate cancer screening, and occurrence of colonoscopy for colon cancer screening. Results: As shown in table, a higher financial hardship score was associated with a decreased odds ratio for having a PSA test of 0.916 (95% CI 0.867-0.967, p=0.002) and colonoscopy of 0.969 (95% CI 0.941-0.998, p=0.039). Conclusions: Worse financial hardship is associated with a decreased probability of having PSA or colonoscopy screening tests. Awareness of this specific toxicity needs to be raised, examining the association of financial toxicity and screening of prostate, colon, and other additional cancers. [Table: see text]

56 Background: Mental illness is a growing issue in the USA. More individuals continue to be diagnosed with illnesses such as depression and anxiety and placed on necessary medications. Studies have shown that the psychological makeup of an individual greatly impacts their health behavior and usage of preventative measures. However, there is limited research on the effect of anxiety and depression on PSA testing. This study explores the associations between the use of anxiety and depression medications and PSA testing. Methods: We used data from the National Health Interview Survey during the year 2018, and assessed responses to the question “Have you ever had a PSA test?” and “What is the number of PSA tests you had in the last 5 years?”. Responses were stratified by whether men were taking medications for anxiety, depression, both or none. We performed multivariable logistic regression analysis to define adjusted odds ratios of undergoing PSA testing adjusting for relevant socio-economic and demographic parameters. Results: Among the 5,035 male participants, 89.4% did not take any medication, 2.9% reported they took anxiety medication, 2.1% took depression medication and 5.5% took both medications. There was a significantly higher rate of PSA testing in men who took medications for both anxiety and depression compared to men taking no medications (p=0.002). Furthermore, the average number of PSA tests in the last 5 years was highest in the group of men taking both medications ( p < 0.0001). Multivariable analysis showed that men who took medications for both depression and anxiety were more likely to undergo PSA testing in comparison to men, not on any of these medications (OR=1.755, p=0.001). The multivariable analysis also showed that age, living with a spouse, and prior cancer history were associated with an increased likelihood of PSA testing while being a minority, living in the south of the USA, and being a current smoker was associated with a lower likelihood of undergoing PSA testing. Conclusions: Taking both anxiety and depression medications in men may be associated with a higher likelihood of undergoing PSA testing. Despite obvious limitations of this analysis including its retrospective nature and recall bias, this association needs to be further explored, especially due to rising use of these medication in the current era of the COVID-19 pandemic.[Table: see text]

TPS593 Background: Treatment options are limited for patients with high-risk non-muscle-invasive bladder cancer (HR-NMIBC) unresponsive to intravesical bacillus Calmette–Guérin (BCG). TAR-200 is an intravesical drug delivery system for local continuous release of gemcitabine within the bladder. The current study will assess the rate of complete response (CR) upon treatment with TAR-200 + systemic cetrelimab (CET [anti–PD-1 antibody]), TAR-200, and CET in BCG-unresponsive participants with HR-NMIBC who are ineligible for or decline radical cystectomy (RC). Methods: SunRISe-1 (NCT04640623) is an open-label, parallel-group, multicenter phase 2b study designed to assess the efficacy and safety of TAR-200 + CET, TAR-200 alone, and CET alone in participants with BCG-unresponsive HR-NMIBC. Eligible participants are aged ≥ 18 years with ECOG PS 0, 1, or 2 and recurrent or persistent histologically confirmed HR-NMIBC (carcinoma in situ) with or without papillary disease (T1, high-grade Ta), who have been diagnosed within 12 months of last BCG treatment and are ineligible for or declined RC. Participants (N≈200) are randomized 2:1:1 to receive TAR-200 + CET (Cohort 1, n≈100), TAR-200 (Cohort 2, n≈50), or CET (Cohort 3, n≈50). In Cohorts 1 and 2, participants receive intravesical TAR-200 every 3 weeks through Week 24, and every 12 weeks thereafter until Week 96. In Cohorts 1 and 3, participants receive CET until Week 78. Primary disease assessments (cystoscopy, urine cytology, transurethral resection of bladder tumor [TURBT], and magnetic resonance imaging/computed tomography) are made at baseline; subsequent cystoscopy and centrally read urine cytology are performed every 12 weeks through Year 2, every 24 weeks until end of Year 3, and in Year 4 and Year 5 in accordance with institutional standards of care. TURBT is conducted at 24 and 48 weeks. The primary end point for the 3 cohorts is overall CR rate at any time point. Secondary end points include duration of response (ie, from time of first CR achieved to first evidence of recurrence, progression, or death [whichever is earlier] for participants who achieve a CR), overall survival, PK immunogenicity of cetrelimab, safety and tolerability, and patient-reported outcomes. Exploratory end points include incidence and time to cystectomy (measured from randomization to date of cystectomy), biomarkers, and health care resource utilization. This study opened in January 2021 and is enrolling participants at ≈165 study sites worldwide. Currently, the study is active in 13 countries with 12 participants enrolled as of September 12, 2021. Clinical trial information: NCT04640623.

230 Background: Prostate specific antigen (PSA) screening remains a controversial issue. However, most urological guidelines recommend PSA testing through a shared decision-making process with the patient. The rate of PSA screening in men with a history of cancer compared to men with no cancer history is not well known. We aimed to compare PSA testing in men aged 55-69 years with and without a history of cancer (excluding prostate cancer patients). Methods: Utilizing the National Health Interview Survey (NHIS) a retrospective cross-sectional study between the years 2015 and 2018 was carried out to analyze and compare PSA testing rates in men aged 55-69 years. Multivariable logistic regression model was implemented do demonstrate potential associations with PSA testing. Results: A total of 13,850 men aged 55-69 years included in the NHIS Survey were analyzed. 1519 (10.9%) men had a history of cancer (non-prostate). On multivariable analysis, men who were previously diagnosed with cancer had a higher rate of PSA testing compared to men with no history of cancer (OR: 1.88, 95% CI 1.39-2.54, p < 0.001). Other factors associated with an increased likelihood of undergoing PSA testing included: age, homosexual orientation, and married men. In contrast, current smokers, American Indians and Alaskan Natives and Asians were less likely to undergo PSA testing. Conclusions: Our data suggest that men aged 55-69 with a history of cancer are more likely to undergo PSA testing than men with no cancer history.[Table: see text]

156 Background: NEPC is a high-grade aggressive form of prostate cancer. We queried whether RB1 mutation status would impact the genomic features of NEPC. We hypothesized that there would be differences in GA frequencies in RB1 mutated vs non mutated cases. Methods: From a series of 13,496 cases of clinically advanced PC, 415 (3.1%) histologically defined NEPC were sequenced using a hybrid capture-based FDA-approved clinical genomic profiling (CGP) assay to detect all classes of genomic alterations (GA). Tumor mutational burden (TMB) was determined on 0.8 Mbp of sequenced DNA and microsatellite instability (MSI) was determined on 95 loci. PD-L1 expression was determined by IHC (Dako 22C3) with low tumor cell positive staining 1-49% and high staining ≥50% expression. Results: 253 (61%) of NEPC feature GA in RB1 (RB1 mut+). This contrasts with a 5.8% frequency of RB1 GA in the non-NEPC (P

164 Background: Novel treatments for clinically advanced GUca including castrate resistant prostate ca (PC), bladder urothelial ca (BUC) and clear cell renal ca (ccRCC) are widely needed. Recently, the targeting of cancer cells with arginine accumulation caused by MTAP loss has emerged as a new synthetic lethality-based anti-cancer program. Methods: 8,436 mCRPC, 2,683 BUC and 841 ccRCC underwent hybrid-capture based comprehensive genomic profiling (CGP) to evaluate all classes of genomic alterations (GA). Tumor mutational burden (TMB) was determined on up to 1.1 Mbp of sequenced DNA and microsatellite instability (MSI) was determined on up to 114 loci. PD-L1 tumor cell expression was determined by IHC (Dako 22C3). Results: 1.3% of PC, 24.2% of BUC and 5.5% of ccRCC featured MTAP loss. There were no significant age or gender differences associated with MTAP loss. CDKN2A/B loss ranged from 94% in ccRCC to > 99% in PC and BUC. The GA/tumor frequencies were similar when CDKN2A/B GA are excluded. In PC, GA in TP53, PTEN and BRCA1 were more frequent, while GA in AR, CDK12, RB1 and BRCA2 were less frequent in cases with MTAP loss. In BUC, GA in TSC1 and FGFR3 were more frequent and GA in RB1and TP53 were less frequent in cases with MTAP loss. In ccRCC, GA in NF2 were more frequent in cases with MTAP loss, while GA in VHL and PBRM1 were less frequent in cases with MTAP loss. “Targetable” kinase GA were rare in all groups, except for FGFR3 GA in MTAP loss BUC. Immunotherapy (IO) putative biomarkers varied among tumors, with MSI-high status less frequent and TMB ≥ 10 mut/Mb more frequent in BUC MTAP-intact than BUC with MTAP loss. PD-L1 expression was similar except for high PD-L1 expression more frequent in MTAP-intact BUC. Conclusions: When compared with PC and ccRCC, the clinical development of novel drugs, such as PRMT5 and MTA2 inhibitors in GUca will likely be focused on BUC given the 24% frequency of MTAP loss in that tumor type. CGP of PC, BUC and ccRCC reveal significant differences in GA in MTAP-intact and tumors with MTAP loss, which may impact future combinatorial clinical trial designs.[Table: see text]

563 Background: Immunohistochemistry (IHC) to determine PD-L1 expression level has been proposed a companion assay related to the approval of immune checkpoint inhibitors in UBC. We hypothesized that the GA profiles would differ between UBC featuring high vs negative PD-L1 expression. Methods: 102 cases of advanced UBC with known PD-L1 expression underwent hybrid-capture based comprehensive genomic profiling to evaluate all classes of GA. Tumor mutational burden (TMB) was determined on up to 1.1 Mbp of sequenced DNA and microsatellite instability (MSI) was determined on 114 loci. Tumor cell (TC) PD-L1 expression was determined by IHC (Dako 22C3). Only PD-L1 high (H) (≥50% TC expression) and negative (N) (0% TC expression) cases were included with PD-L1 Low (1-49% TC expression) cases excluded from this study. Results: Overall, only 2 (8.3%) of the 24 PD-L1H UBC featured CD274 ( PD-L1) amplification (mean 19 copies) and none of 78 PD-L1N had CD274 amp (P =.05). The gender, age was similar in the groups. When compared with the PD-L1H UBC cases, FGFR3 GA were significantly more frequent in the UBC PD-L1N cases (p =.02). Currently “untargetable” GA that were more frequent in the PD-L1H UBC, but did not reach statistical significance, included TP53, TERT and RB1. MTAP loss, a potential target for PRMT5 and MTA2 inhibitors, were 3X more frequent in the PD-L1N UBC. ERBB2 amplification and ERBB3 and PIK3CA short variant (SV) GA were more frequent in the PD-L1N UBC with differences not reaching significance. Other ICPI-associated potential biomarkers, including MSI status, TMB level and GA in PBRM1, STK11 and MDM2 were not significantly different in the groups. For UBC cases where a mutational signature could be determined, 10/12 (83%) of PD-L1H and 21/29 (72%) of PD-L1N UBC featured APOBEC signature; 2 PD-L1N featured MMR signature and 6 PD-L1N UBC featured no dominant signature. Conclusions: PD-L1H and PD-L1N subtypes of UBC differ in their genomic profiles:PD-L1N UBC features greater frequencies of potentially “targetable” GA, including FGFR3, ERBB2, ERBB3 and PIK3CA. PD-L1 IHC may thus not only play a role in the selection of ICPI for advanced UBC but also in designing trials that may combine ICPI with targeted therapies. Limitations include small sample size, possible selection bias and lack of clinical annotation.[Table: see text]

443 Background: Electronic cigarette smoking and similar novel smoking modalities have raised questions about their impact on various cancers compared with traditional forms of tobacco smoking. Tobacco smoking has been concretely proven to increase the risk of many cancers, including lung (LCa) and bladder (BCa) cancer. To date, there is little data on how e-cigarette smoking impacts the incidence of these cancers. We investigated whether any disparities exist in the prevalence of LCa and BCa between various smoking histories using a US nationally representative data source. Methods: This cross-sectional survey-based US study included men and women aged 18+ from the National Health Interview Survey (NHIS) database between 2016-2018. Primary endpoint was self-reported occurrence of LCa and BCa diagnosis. Multivariable logistic regression analyses assessed possible association of various covariates with diagnosis of these cancers. Results: Prevalence of BCa and LCa was higher in all smoking histories compared to never smokers. Patients with a history of e-cigarette smoking vs. no history of e-cigarette smoking were significantly younger at BCa diagnosis (56.87 [±9.86] vs. 65.00 [±12.60] years, p=0.001). Multivariable logistic regression models showed that a history of cigarette smoking and e-cigarette smoking individually was associated with increased ORs of 2.476 (p≤0.001) and 1.577 (p≤0.001) for BCa diagnosis, respectively, and 4.589 (p≤0.001) and 1.614 (p=0.007) for LCa diagnosis, respectively. Conclusions: Compared to never smokers, history of e-cigarette smoking was associated with increased risk of LCa and BCa development and earlier BCa diagnosis. Additional studies are needed to better define the public health effects of these novel and unregulated products.

292 Background: FLCN is a tumor suppressor gene associated with cutaneous hair follicle development. FLCN germline mutations are linked to inherited chrRCC in the Birt-Hogg-Dube (BHD) syndrome. We queried whether clinically sporadic chrRCC featured FLCN mutations by comparing the genomic profiles of chrRCC with ccRCC. Methods: 108 chrRCC and 2110 ccRCC underwent hybrid-capture based comprehensive genomic profiling (CGP) to evaluate all classes of genomic alterations (GA). Tumor mutational burden (TMB) was determined on up to 1.1 Mbp of sequenced DNA and microsatellite instability (MSI) was determined on 114 loci. PD-L1 expression was determined by IHC (Dako 22C3). Results: Patients (pts) with chrRCC were more frequently female and younger than pts with ccRCC p

129 Background: Data on heterogeneity in cancer screening and diagnosis rates among lesbians/gays and bisexuals is lacking. Recent studies showed that lesbians/gays and bisexuals have decreased healthcare utilization compared to heterosexual counterparts and continue to experience discrimination in healthcare. Few studies have examined how sexual orientation impacts cancer screening and prevalence. We, therefore, investigated the association between sexual orientation and prevalent sex-specific cancer including prostate, breast, and cervical cancer. Methods: This was a cross-sectional survey-based US study, including men and women aged 18+ from the Health Information National Trends Survey (HINTS) database between 2017-2019. The primary endpoint was individual-reported prostate, breast, and cervical cancer screening and prevalence rates among heterosexual and LGB men and women. Multivariable logistic regression analyses assessed association of various covariates with undergoing screening and diagnosis of these cancers. Results: Overall, 4,441 and 6,333 heterosexual men and women, respectively, were compared to 225 and 213 lesbian/gay and bisexual men and women, respectively. Lesbians/gays and bisexuals were younger and less likely to be screened for prostate, breast, and cervical cancer than heterosexuals. A higher proportion of heterosexual women than lesbian and bisexual women were screened for cervical cancer with pap smears (95.36% vs. 90.48% and 86.11%, p = < 0.001) and breast cancer with mammograms (80.74% vs. 63.81% and 45.37%, p = < 0.001). Similarly, a higher proportion of heterosexual men than gay and bisexual men were screened for prostate cancer with PSA blood tests (41.27% vs. 30.53% and 27.58%, p = < 0.001). Conclusions: Lesbians/gays and bisexuals in the US may be less likely to undergo screening of sex-specific prevalent malignancies, including prostate, breast, and cervical cancer. Healthcare professionals should be encouraged to improve cancer screening among lesbians/gays and bisexuals.

5062 Background: Loss-of-function genomic alterations (GAs) in MSH6 have been associated with a unique subtype of hypermutated mCRPC that is often microsatellite stable (MSS) and may occur in either a sporadic or familial Lynch Syndrome-like clinical setting. Methods: 5,617 mCRPC cases were sequenced to evaluate all classes of GA using a hybrid capture-based FDA-approved comprehensive genomic profiling (CGP) assay. Tumor mutational burden (TMB) was determined on 0.8 Mb of sequenced DNA and microsatellite instability high (MSI-High) was determined on 95 loci. MSI-low status was not assessed. Results: 78 (1.4%) mCRPC were MSH6mut (Table). MSH6mut mCRPC included 73.1% short variant mutations, 23.1% biallelic deletions, 2.6% genomic rearrangements, and 1.3% multiple GAs/sample. Co-mutation of MSH2 was found in 28% of MSH6mut cases vs. 2% in MSH6wt cases (P mut mCRPC, which was significantly greater than the 2% seen in MSH6wt cases (P mut cases, compared to 3% MSH6wt cases (P mut cases with neither MSI-High nor MMR mutational signature, 87% did not have biallelic loss of MSH6 or any other MMR gene, confirming that monoallelic pathogenic mutations are insufficient to cause the MMR-D phenotype. For subjects whose variants could be classified, 45% (19/42) of pathogenic MSH6 alleles were germline; of these, 58% (11/19) had neither MSI-High nor an MMR single nucleotide signature. MSH6mut cases had fewer TMPRSS2: ERG fusions (P =.01), but harbored significantly higher frequencies of GAs in AR (P =.0002), ATM (P =.04), PIK3CA (P =.0003), APC (P =.005), ERBB2 (P =.001), and CDK6 (p =.046), likely at least partially attributable to the higher TMB in MSH6mutcases (P mut mCRPC is a unique disease that often features a hypermutated genomic signature, although only 46% of cases exhibited MSI-high status. This complex phenotype highlights the potential utility of multiple rather than single biomarkers to understand tumor biology and determine patients who may benefit from immunotherapy.[Table: see text]

6506 Background: Data on heterogeneity in cancer screening and diagnosis rates among sexual minorities (SMs) is lacking. Recent studies have shown SMs are more likely to engage in risky health behavior and have decreased healthcare utilization compared to heterosexual counterparts. However, few studies have examined how sexual orientation (SO) impacts cancer screening and prevalence. We therefore investigated whether SO affects prevalent gender-specific cancer screening and prevalence, including prostate (PCa), breast (BC), and cervical cancer (CC). Methods: This was a cross-sectional survey-based US study, including men and women aged 18+ from the Health Information National Trends Survey (HINTS) database (part of the National Cancer Institute’s division of cancer control and population sciences) between 2017-2019. The primary endpoint was individual-reported PCa, BC, and CC screening and prevalence rates among heterosexual and SM men and women. Multivariable logistic regression analyses assessed association of various covariates with undergoing screening and diagnosis of these cancers. Results: Overall, 4,441 (95.18%) men and 6,333 (96.75%) women reported a SO of heterosexual whereas 167 (3.6%) and 58 (1.2%) men and 105 (1.6%) and 108 (1.6%) women reported a SO of gay and bisexual, respectively. Mean age was higher in the heterosexual group compared to the gay and bisexual groups in both men (57.7 [±16.0] vs. 52.4 [±14.5] and 51.9 [±18.0] years, p = < 0.001) and women (56.2 [±16.7] vs. 49.0 [±17.1] and 40.0 [±14.8] years, p = < 0.001). Homosexuals and bisexuals were less likely to be screened for PCa (30.53% and 27.58% vs 41.27%, p = < 0.001), BC (63.81% and 45.37% vs 80.74%, p = < 0.001), and CC (90.48% and 86.11% vs 95.36%, p = < 0.001) than their heterosexual counterparts. While rates of PCa and BC diagnoses were similar across SO, more homosexual and bisexual women were diagnosed with CC compared to their heterosexual counterparts (4.76% and 3.70% vs 1.85%, p = 0.039). Multivariable logistic regression models showed that SMs were less likely to be screened for cancer with ORs of 0.61 (95% CI 0.39-0.95, p = 0.030) for PCa, 0.52 (95% CI 0.30-0.92, p = 0.025) for BC, and 0.21 (95% CI 0.09-0.46, p = < 0.001) for CC. Although multivariable models did not show that SMs were more likely to be diagnosed with PC, BC, or CC, SMs were more likely to be diagnosed with any cancer with ORs of 1.64 (95% CI 1.06-2.54, p = 0.026) in women only and 1.50 (95% CI 1.11-2.03, p = 0.009) in men and women combined. Conclusions: These data suggest that in addition to other established and known specific socio-economic risk factors, SMs may be less likely to undergo screening of prevalent malignancies such as PCa, BC, and CC. This provides more evidence of ongoing healthcare inequality, urging our healthcare system to invest more in cancer screening of this vulnerable population.

1525 Background: Studies show that cancer patients and survivors are likely to endure financial toxicity long after being diagnosed. Methods: To examine the influence of race on financial toxicity among individuals with a history of cancer, a US based cross sectional study was conducted using data on 1,328 cancer patients collected from the Health Information National Trends Survey. Multivariable logistic regression analyses were used to analyze the relationship between race and financial toxicity, adjusting for known confounders. Results: Blacks, Hispanics and other races were shown to have a lower rate of insurance compared to Whites. Whites were also more likely to receive cancer treatment than other races (6.1% received no treatment vs 15.0% of Blacks, 17.8% of Hispanics, and 9.7% of other races, p

3130 Background: Given that the clinical manifestations, disease course, and treatment options for pSCC differ between tumor types, we performed CGP to examine possible genomic differences. Methods: 1,741 clinically advanced pSCCs including 230 penile (penSCC), 17 male urethral (murthSCC), 125 male anal (manSCC), 7 female urethral (furthSCC), 263 vulvar (vulSCC), 822 cervical (crvSCC), and 277 female anal SCCs (fanSCC) underwent hybrid capture-based CGP to evaluate all classes of genomic alterations (GAs). Tumor mutational burden (TMB) was determined on up to 1.1 Mb of sequenced DNA and microsatellite instability (MSI) was determined on up to 114 loci. PD-L1 expression was determined by IHC (Dako 22C3). Results: HPV-16/18 detection was lowest in murthSCC and vulSCC and highest in manSCC, fanSCC, and crvSCC. TP53 GAs were inversely associated with HPV status. PIK3CA GA frequency varied (22-43%). DNA-damage response (DDR) GAs (e.g., BRCA1/2, ATM, others) were low ( < 1-3%) throughout. Cell-cycle GAs were most frequent in external cases (penSCC, furthSCC, vulSCC). MTOR pathway GAs ( PTEN, FBXW7) were the most frequently identified “actionable” GAs. FGFR3 GA were present in >5% of murthSCC, crvSCC, and fanSCC; other receptor-tyrosine kinase (RTK) targeted options were 1% in BRAF/ ERBB2. NOTCH1 GAs were present in > 15% of penSCC and vulvSCC. TMB ≥10 mut/Mb was >15% in manSCC, fanSCC, and crvSCC. PD-L1 low expression was > 25% in all pSCC except crvSCC and high expression was > 18% in all pSCC except urthSCC and manSCC. Conclusions: Despite similar histology, pSCC differ widely in GAs and HPV status. PIK3CA is the most frequent “targetable” GA followed by MTOR pathway and cell cycle; RTK targets are extremely rare. PARP inhibitor options appear low given the infrequent finding of DDR GAs. Anti-PD(L)1 could be considered in a number of cases based on TMB>10 mut/Mb and PD-L1 expression.[Table: see text]

349 Background: srcRCC is a well-described histologic entity often featuring rapid progression and aggressive clinical course when compared with classic ccRCC. We queried whether CGP would uncover opportunities for targeted and immunotherapy (IO) for srcRCC patients that could individualize their treatment and entry into clinical trials. Methods: Using a hybrid capture-based CGP assay to evaluate all classes of genomic alterations (GA), 160 cases of srcRCC and 1,664 cases of ccRCC were sequenced from FFPE tissue samples. Tumor mutational burden (TMB) was determined on up to 1.1 Mbp of sequenced DNA and microsatellite instability (MSI) was determined on up to 114 loci. PD-L1 expression was determined by IHC (Dako 22C3) with low tumor cell positive staining set at 1-49% and high staining >50% expression. Results: Gender and age distributions for both tumor types were similar. srcRCC featured significantly higher GA/tumor than ccRCC (P < .0001). CGP revealed major differences with ccRCC associated more frequently with tumor suppressor gene (TSG) losses in VHL, PBRM1, TSC2 and SETD2 (all P < .0001). In contrast, srcRCC is associated with cell proliferation with increased inactivation of cell cycle regulatory genes including TP53, CDKN2A/B, MDM2 and TERT (all P < .0001). RB1 GA in srcRCC may reflect neuroendocrine differentiation occasionally found in these tumors. NF2 GA were more frequent in srcRCC (P < .0001). Conclusions: CGP reveals striking differences between srcRCC and ccRCC which may in part explain the differing histologic appearances and typical clinical course of these 2 aggressive malignancies. ccRCC is driven more by TSG loss and srcRCC is driven more by cell cycle dysregulation. Targeted therapy opportunities were uncommon for both tumor types although each featured biomarkers potentially predictive of mTOR inhibitor responses ( TSC2 in ccRCC and NF2 in srcRCC). Although the higher PBRM1 GA frequency in ccRCC may explain the IO benefit well-known for this tumor type, the srcRCC group features significantly increased TMB, CD274 amplification and PD-L1 staining which may also create IO opportunities for srcRCC patients. [Table: see text]

485 Background: When UCB presents or progresses to chemorefractory metastatic disease, the search for new therapy targets is paramount. Targeting PRMT5 arginine methyltransferase accumulation in tumors with MTAP (methylthioadenosine Phosphorylase) genomic loss has been proposed as a new SL based anti-tumor strategy and under consideration for development for UCB. We sought to evaluate the incidence of patients with candidate SL and correlate to treatment-guiding biomarkers currently evaluated in SOC. Methods: 2,683 cases of clinically advanced UCB underwent hybrid-capture based comprehensive genomic profiling in a standard of care setting using the F1CDx FDA-approved assay to evaluate all classes of genomic alterations (GA) among 324 genes. Tumor mutational burden (TMB) was determined on 0.8 Mbp of sequenced DNA and microsatellite instability (MSI) was determined on 95 loci. PD-L1 expression was determined by IHC (Dako 22C3). Results: 650 (24%) of UCB feature MTAP loss (MTAP-) (Table). The gene and age distributions were similar MTAP intact (MTAP+) and MTAP- UCB. The GA/tumor was higher in MTAP- UCB likely reflecting the significant GA co-deletions of CDKN2A/ B at the 9p21 locus. Of potential therapeutic targets, FGFR3 and PTEN GA were more frequent in the MTAP- UCB. In contrast, biomarkers of immunotherapy (IO) response included higher frequencies of high TMB and high PD-L1 IHC staining in the MTAP+ UCB. Conclusions: When compared with MATP+ UCB, MTAP- UCB differs in genomic signatures including an increase in potential for targeted therapies but a lower potential for IO drug benefit. Thus, the genomic landscape in MTAP- UCB may play a significant role in the design of clinical trials incorporating SL strategies when targeting PRMT5 in MTAP deficient tumors. [Table: see text]

198 Background: Data on heterogeneity in cancer screening and diagnosis rates among sexual minorities (SMs) is lacking. Recent studies have shown SMs are more likely to engage in risky health behavior and have decreased healthcare utilization. However, few studies have examined how sexual orientation impacts cancer screening and prevalence. We therefore investigated whether sexual orientation affects prevalent gender-specific cancer including prostate (PCa), breast (BC), and cervical cancer (CC). Methods: This was a cross-sectional survey-based US study, including men and women aged 18+ from the Health Information National Trends Survey (HINTS) database (part of the National Cancer Institute’s division of cancer control and population sciences) between 2017-2019. The primary endpoint was individual-reported PCa, BC, and CC screening and prevalence rates among heterosexuals and homosexuals/bisexuals. Multivariable logistic regression analyses assessed association of various covariates with undergoing screening and diagnosis of these cancers. Results: Overall, 4,441 and 6,333 heterosexual men and women, respectively, were compared to 225 and 213 homosexual/bisexual men and women, respectively. Homosexuals/bisexuals were younger and less likely to be screened for PCa (34.7% vs 41.3%, p=0.013), BC (54.5% vs 80.7%, p=

481 Background: mBSCC is an uncommon form of urinary bladder malignancy when compared with the much higher urothelial carcinoma incidence. We studied the genomic alteration (GA) landscape in a series of mBSCC based on the association with HPV-16 to determine if differences would be observed between the positive and negative groups. Methods: Using a hybrid capture-based FDA-approved CGP assay, a series of 171 mBSCC were sequenced to evaluate all classes of GA. Tumor mutational burden (TMB) was determined on up to 1.1 Mbp of sequenced DNA and microsatellite instability (MSI) was determined on 114 loci. PD-L1 expression was determined by IHC (Dako 22C3) with low tumor cell positive staining set at 1-49% and high staining at ≥50% expression. Results: Overall, 11 (6.4%) of the mBSCC were found to harbor HPV-16 sequences (Table). HPV-16+ status was identified slightly more often in women (NS) and in younger patients (P = .04); 2 female patients with mBSCC had prior history of SCC including 1 anal SCC and 1 vaginal SCC. HPV-16+ mBSCC had fewer GA/tumor (P < .0001), and fewer inactivating GA in CDKN2A (P < .0001), CDKN2B (P = .05), TERT promoter (P = .0004) and TP53 (P < .0001). GA in genes associated with urothelial carcinoma including FGFR2 and FGFR3 were similar in both HPV-16+ and HPV-16- mBSCC groups. MTOR and PIK3CA pathway GA were not significantly different in the 2 groups. MSI and TMB were also similar in the 2 groups. The 3 HPV-16+ mBSCC cases showed high positive PD-L1 IHC staining. Conclusions: HPV-16+ mBSCC tends to occur more often in women and younger patients. As reported in other HPV-associated squamous cell carcinomas, HPV-16+ mBSCC demonstrates significantly reduced frequencies of inactivating mutations in cell cycle regulatory genes with similar GA in MTOR and PIK3CA pathways. The implication of HPV in the pathogenesis of bladder cancer remains unknown but warrants further exploration and clinical validation. [Table: see text]

165 Background: Identifying prostate cancer patients likely to benefit from immune checkpoint inhibitors (ICPI) remains an unmet need. Specific loss-of-function genomic alterations (GA) in CDK12 are associated with focal tandem duplications linked to fusion-induced production of neoantigens and are a promising candidate biomarker for ICPI. Using comprehensive genomic profiling (CGP) we compared the GA landscape of CDK12 altered (CDK12mut+) and unaltered (CDK12mut-) tumors. Methods: 4,918 mCRPC tumors were sequenced using a hybrid capture-based FDA-approved CGP assay. Tumor mutational burden (TMB) was determined on 0.8 Mbp of sequenced DNA and microsatellite instability (MSI) was determined on 95 loci. PD-L1 expression was determined by IHC (Dako 22C3) with low tumor cell positive staining -49% and high staining ≥50% expression. Results: Overall, 315 (6.4%) of the mCRPC cases were CDK12mut+ (Table). CDKmut+ cases had significantly fewer GA in TMPRSS2: ERG (P < .0001), TP53 (P < .0001), PTEN (P < .0001), ATM (P = .001), PIK3CA (P = .003), RB1 (P = .02), BRCA2 (P < .0001) and APC (P = .002). CDK12mut+ cases featured higher frequencies only in CCND1 (P < .0001), BRAF (P = .007) and ERBB2 (P < .001) as well as in cell cycle regulatory genes including MDM2/4 (P < .0001), CDK4 (P < .0001) and CDK6 (P = .002). CDK12mut+ cases featured more frequent MSI-H status (P = .007), significantly higher median TMB (P < .001) and more frequent low positive (1-49% staining) PD-L1 expression (P = .02). High (≥50%) PD-L1 expression was rarely identified in either cohort. Conclusions: CDK12mut+ mCRPC demonstrates a unique genomic profile with significant differences compared with CDK12mut- mCRPC. Lower frequencies of GA associated with homologous recombination defect and mTOR pathway may impact the use of platinum agents, as well as PARPi and PIK3CA/Akt/mTOR inhibitors. Opportunities for targeted therapies for BRAF and ERBB2 driven mCRPC may be enriched in the CDK12mut+ tumors and raise the possibility of combination therapy strategies although the numbers of patients are small and validation is needed. The slightly higher MSI High status, median TMB and PD-L1 staining may be associated with additional benefit from ICPI and warrants further prospective investigation. [Table: see text]

163 Background: Herpesvirus HHV-8 has been detected in normal prostate tissue and has been linked to the acquisition of androgen-independent growth of prostate cancer cells in vitro, early development of anti-androgen therapy resistance, and more aggressive disease in a subset of patients with mCRPC. We used comprehensive genomic profiling (CGP) to test the hypothesis that HHV-8 associated mCRPC is a distinct molecular subset of mCRPC featuring altered AR signaling compared to HHV-8 negative mCRPC. Methods: Using a hybrid capture-based FDA-approved CGP assay, a series of 4,918 mCRPC were sequenced to evaluate all classes of genomic alterations (GAs). Tumor mutational burden (TMB) was determined on up to 1.1 Mb of sequenced DNA and microsatellite instability (MSI) was determined on 114 loci. PD-L1 expression was determined by IHC (Dako 22C3). HHV-8 status was determined by CGP-based identification of unique viral reads. Results: Overall, 128 (2.6%) of the mCRPC cases harbored HHV-8 sequences (Table). The patient age distribution was similar in the HHV-8+ and HHV-8− groups. GAs in AR, predominantly amplifications, and RAD21 were slightly reduced in HHV-8+ mCRPC cases (P = .01 for both). The frequencies of GAs in genes associated with mCRPC including PTEN, BRCA2, ATM, CDK12, and the TMPRSS2: ERG fusion were similar in the two groups. HHV-8+ patients were less likely to be of European ancestry (P = 0.001). Putative biomarkers associated with immunotherapy response (MSI status, TMB, and PD-L1 expression) were also similar in the two groups. Conclusions: HHV-8+ mCRPC is a rare sub-type of mCRPC with lower frequency of AR GAs compared to HHV-8− mCRPC cases, suggesting a potential role of HHV-8 in inducing androgen-independent prostate cancer growth. Additional alterations associated with potentially enhanced PARP inhibitor response seen in HHV-8+ mCRPC (e.g., RAD21) suggest that early performance of CGP may inform precision treatment strategies to be tested in clinical trials. [Table: see text]

2 Background: Although SCC of the penile skin (pSCC) and the male urethral surface epithelium (uSCC) arise in nearby locations and can feature similar histology, their clinical manifestations, disease course, and surgical and medical treatment options are distinct. We performed CGP on pSCC and uSCC to examine genomic profiles differences. Methods: Tissues obtained from men with clinically advanced pSCC (n = 230) and uSCC (n = 17) underwent hybrid capture-based CGP to evaluate all classes of genomic alterations (GAs). Tumor mutational burden (TMB) was determined on up to 1.1 Mb of sequenced DNA and microsatellite instability (MSI) was determined on up to 114 loci. PD-L1 expression was determined by IHC (Dako 22C3). Results: The median ages were similar in both groups. pSCC exhibited a slightly higher frequency of HPV-16/18 infection (29% vs. 12%, P = .16), although the TP53 mutation frequencies were nearly identical (55% vs. 59%, NS). CDKN2A inactivation (P = .08), CCND1 amplification trending higher and TERT promoter mutations (P = .01) were more frequent in pSCC, potentially indicating prior HPV infection. GAs in NOTCH1 were exclusively identified in pSCC. Potentially actionable GAs identified in both groups included PIK3CA activating mutations (TKIs) as well as pathogenic alterations in FBXW7 and PTEN (MTOR inhibitors). Rare BRCA1 and BRCA2 inactivation (PARP inhibitors) was seen in pSCC only. High-positive PD-L1 staining was elevated in pSCC (34 vs. 14%, P = .06). Although average TMB was similar in both groups, pSCC exhibited an elevated frequency of cases with CD274 ( PD-L1) amplification as well as TMB >10 mut/Mb which are on label for immune checkpoint inhibitor (ICPI) treatment. Conclusions: CGP of pSCC and uSCC identifies opportunities for both targeted and ICPI therapies. Compared to uSCC, pSCC had genomic features more similar to head and neck SCC including slightly increased cell-cycle perturbation, HPV infection, and NOTCH pathway signaling alterations. Further use of CGP in the treatment planning for pSCC and uSCC may be warranted. [Table: see text]

5534 Background: Comprehensive genomic profiling (CGP) was done on pre-systemic treatment (pre) PT, post-treatment (post) MET sites and LB in PC to uncover differences in genomic alterations (GA) and potential impact on therapy selection. Methods: 1,294 PC tissues and 782 LB underwent hybrid-capture based CGP. PT biopsies and resections were compared with post-treatment MET biopsies from bone (BO), liver (LIV), lung (LU), brain (BN), lymph node (LN) and soft tissue (ST) sites and LB. TMB was determined on up to 1.1 Mbp of sequenced DNA for tumor samples. Tumor cell PD-L1 IHC was measured (Dako 22C3). Results: Differences in alteration frequencies between PT, MET and LB for selected genes are shown in the Table. TMPRSS2:ERG fusion frequencies were similar between PT and MET (35% vs 33%) but varied between MET sites (27% in BO and ST to 40% in LN). GA in AR were lowest in pre PT (2%) and highest in MET (24% in LU to 50% in LIV). BN had the highest GA/tumor (8) and the most PTEN GA. BRCA2 GA frequency varied from 0% in BN to 15% in LI. Potential predictors of IO response included CDK12 GA (16% in LU) and MSI high status (29% in BN). High PD-L1 expression was found in only two cases (LN) and low PD-L1 expression was relatively uncommon. ERBB2 amplifications were increased in MET compared with PT. RB1 GA were increased in LIV cases. LB GA had a similar increase in AR and TP53 GA to MET and appeared to be a blend of MET site biopsies across alteration frequencies. Conclusions: CGP of PT, MET and LB in PC demonstrates differences most likely associated with exposure to systemic therapies. Differences identified in the MET GA landscape suggest that liquid biopsies may capture a broader range of therapeutic opportunities for PC patients. [Table: see text]

5066 Background: We queried whether the landscape of genomic alterations (GA) would differ in patients with metastatic RCC under 40 years of age (under40) and patients 40 years of age or older (over40). Methods: FFPE tissues from 2,128 clinically advanced RCC and 25 RSC underwent hybrid-capture based CGP to evaluate all classes of GA. Samples were classified at time of sequencing as the following RCC subtypes: clear cell (ccRCC), papillary (papRCC), chromophobe (chrRCC), medullary (medRCC), collecting duct (cdRC), sarcomatoid (sarcRCC) and NOS (nosRCC). Tumor mutational burden (TMB) was determined on up to 1.1 Mbp of sequenced DNA. Tumor cell PD-L1 expression was determined by IHC (Dako 22C3). Results: The male preponderance increased in the over40 patients. The GA/tumor increased in the over40 cohorts except for medRCC. Similarly, TMB was consistently higher in over40 groups. MSI high status was virtually absent. PD-L1 expression, available only in small subsets, was generally absent although 44% high positive staining in sarcRCC was noteworthy. Differences in GA in under40 vs over40 RCC were seen and included increased PBRM1 and SETD2 GA in over40 vs under40 ccRCC; increased C DKN2A/B and TERT and decreased FH GA in over40 vs under40 papRCC; increased TP53 and decreased VHL, BAP1, SETD2 and PTEN in over40 vs under40 chrRCC; increased TP53, PTEN and TERT GA with decreased NF2 GA in over40 vs under 40 sarcRCC; and increased TP53, VHL and TERT in over40 vs under40 nosRCC. Changes in GA in under40 vs over40 medRCC, cdRCC and RSC were noted but insufficient cases prevented further evaluation. Conclusions: When separately evaluated by under/over 40 years of age, CGP of clinically advanced RCC demonstrates differences in genomic landscapes with over40 cases featuring increasing male preponderance, higher GA/tumor, higher TMB and increases in a variety of GA. These findings may play important roles in the planning of future clinical trials designed to personalize the treatment of metastatic RCC. [Table: see text]

5087 Background: UrthCa is an uncommon GU malignancy that can progress to advanced metastatic disease. Methods: 127 metastatic UrthCa underwent hybrid-capture based CGP to evaluate all classes of genomic alterations (GA). Tumor mutational burden (TMB) was determined on up to 1.1 Mbp of sequenced DNA and microsatellite instability (MSI) was determined on 114 loci. PD-L1 expression was determined by IHC (Dako 22C3). Results: 49 (39%) urothelial (UrthUC), 31 (24%) squamous (UrthSCC), 34 (19%) adenocarcinomas (UrthAC) and 13 (9%) clear cell (UrthCC) were evaluated along with a control cohort of 2,130 bladderUC cases. UrthUC and UrthSCC were more common in men; UrthAC and UrthCC more common in women. Age was similar in all 4 groups. GA in PIK3CA were the most frequent potentially targetable GA; MTOR pathway GA in PTEN also identified. GA in other potentially targetable genes were also identified including ERBB2(6% in UrthUC, 3% in UrthSCC and 12% in UrthAC), FGFR1-3 (3% in UrthSCC), BRAF (3% in UrthAC), PTCH1 (8% in UrthCC) and MET (8% in UrthCC). Higher TMB was seen in UrthUC and UrthCC compared to UrthAC and UrthSCC, possibly reflecting their higher GA/tumor status and suggesting potential for immunotherapy benefit. MSI high status was absent throughout. The bladderUC cases had similar genomic pattern as UrthUC with significantly lower frequency of HPV16/18 positive cases. Conclusions: CGP reveals GA that may be predictive of both targeted and immunotherapy benefit in patients with advanced UrthCa and that could potentially be used in future adjuvant, neoadjuvant and metastatic disease trials. [Table: see text]

175 Background: CGP was performed on Pre PT and Post MET including bone (BO), liver (LIV), lung (LU), brain (BN), lymph node (LN) and soft tissue (ST) mPC. Methods: 1,294 mPC underwent hybrid-capture based CGP. Tumor mutational burden (TMB) was determined on up to 1.1 Mbp of sequenced DNA and microsatellite instability (MSI) was determined on 114 loci. PD-L1 expression was determined by IHC (Dako 22C3). Results: GA in AR were lowest in the Pre PT (2%) and highest in Post LU (24%) and LIV (50%). GA/tumor was significantly higher in BN (8.0) compared to PT (3.8). BR MET also featured higher PTEN GA than PT. BRCA2 GA varied from 0% in BR to 7-9% in PT, BO, LU, LN and ST to a high of 15% in LI MET. ATM GA were significantly higher in LU MET and RAD21 GA highest in LN MET. Potential predictors of IO drug response included high CDK12 GA in LU MET, MSI high status at 29% in BR MET associated with higher TMB levels, but virtual absence of high PD-L1 expression. ERBB2 GA appeared to be increased in the MET group compared with PT but BRAF GA were not. RB1 GA were significantly increased in LIV MET cases. Conclusions: CGP of mPC PT and MET demonstrates significant differences likely linked to exposure to systemic therapies. These findings suggest that, in the future, liquid biopsies may have advantages over individual MET site biopsies in their ability to capture the entire range of therapeutic opportunities for patients with advanced mPC.[Table: see text]

434 Background: KRAS has recently emerged as a druggable driver with novel agents targeting G12C genomic alteration (GA). Methods: FFPE tissue from 1453 renal clear cell carcinomas (RCCC), 3879 urothelial bladder carcinomas (UBC) and 8322 prostate acinar adenocarcinomas (PAAC) underwent comprehensive genomic profiling (CGP). Tumor mutational burden (TMB) was determined on 0.8 to 1.2 Mbp of sequenced DNA and MSI was determined on 114 loci. PD-L1 expression (Dako 22C3) was measured by IHC. Results: KRAS GA were identified in 7 RCCC (

727 Background: We studied the genomic alterations (GA) in patients with mRCC under 40 years of age (40). Methods: 2,128 mRCC underwent hybrid-capture based CGP. Clear cell (ccRCC), papillary (pRCC), sarcomatoid (sRCC), NOS (nosRCC), chromophobe (chrRCC), medullary (medRCC) and collecting duct (cdRCC) were separately evaluated. Tumor mutational burden (TMB) was determined on up to 1.1 Mbp of sequenced DNA and microsatellite instability (MSI) was determined on 114 loci. PD-L1 expression was determined by IHC (Dako 22C3). Results: Male preponderance in all subsets increased in the >40 patients. The GA/tumor increased significantly in the >40 cohorts except for in medRCC. The relatively low TMB was higher in all >40 and MSI high status was infrequent in all groups. PD-L1 expression was generally low, the 44% high positive PD-L1 in sRCC was noteworthy. Significant differences in GA in 40 RCC included increased PBRM1 and SETD2 GA in >40 vs 40 vs 40 vs 40 vs 40 chrRCC, medRCC and cdRCC were noted but insufficient cases prevented statistical evaluation. Conclusions: When evaluated by age, CGP of mRCC demonstrates significant differences in the genomic landscapes with >40 cases featuring increasing male preponderance and higher GA/tumor, TMB and increases in TP53, CDKN2A/B and TERT GA. These findings may play important roles in the planning of future clinical trials designed to personalize the treatment of mRCC.[Table: see text]

726 Background: NF2 genomic alterations (GA) have been associated with aggressive behavior in RCC. Methods: FFPE tissues from 1,386 clear cell (ccRCC), 307 papillary (pRCC), 72 chromophobe (chRCC), 145 sarcomatoid (sRCC), 54 collecting duct (cdRCC),37 medullary (medRCC) and 134 unclassified (nosRCC) underwent hybrid-capture based CGP to evaluate all classes of genomic alterations (GA). Tumor mutational burden (TMB) was determined on up to 1.1 Mbp of sequenced DNA and MSI was determined on 114 loci. PD-L1 expression was determined by IHC (Dako 22C3). Results: 140 (7%) RCC featured NF2 GA which were predominantly short variant (SV) mutations. Gender and age were similar with male preponderance in all histologic subtypes. NF2 GA frequency was highest in cdRCC (20%) and sRCC (19%) and lowest in ccRCC (3%). The medRCC at 5% NF2 GA and chRCC at 0% NF2 GA were not further evaluated. VHL and PBRM1 GA were significantly more frequent in NF2 altered ccRCC than all other RCC (P < 0.001). Other mTOR pathway GA were uncommon. Potentially targetable kinase GA in NF2-mutated RCC included BRAF (2% of ccRCC), EGFR (3% of pRCC), ERBB3 (4% of sRCC) and PIK3CA (9% of cdRCC). No NF2 mutated RCC featured MSI -high status and both TMB and PD-L1 expression levels were extremely low in all subsets with exception of high PD-L1 staining in sRCC tumors. Conclusions: cdRCC, sRCC, pRCC and nosRCC are enriched in NF2 GA. Low PBRM1 GA, TMB and MSI- high predict resistance to immunotherapy in NF2 mutated RCC although the high PD-L1 expression in sRCC is noteworthy.[Table: see text]

5064 Background: PDC, PAC and PNC are histologic subtypes of prostate cancer (PC). We queried whether these subsets would share similar genomic alterations (GA) reflecting their disease biology and clinical features. Methods: CGP was performed using a hybrid capture-based assay on 61 PDC, 4,132 PAC and 217 PNC. Tumor mutational burden (TMB) was determined on 1.1 Mbp of sequenced DNA and microsatellite instability (MSI) was determined on 114 loci. Results: The age, GA per tumor and TP53 GA of PDC, PAC and PNC were similar (Table). RB1 GA were predominant in PNC. TMPRSS2:ERG fusions were most frequent in PNC, intermediate in PAC and lowest in PDC. AR GA were more often identified in PAC than PDC or PNC whereas PTEN GA were most frequent in PDC than PAC or PNC. Targetable GA were identified in all 3 groups when focused on BRCA2 (PARP inhibitors) and PIK3CA (MTOR inhibitors). ATM GA (PARP inhibitors) were more common in PAC than PDC or PNC. BRAF GA (BRAF/MEK inhibitors) were more frequent in PDC and PAC than PNC. CDK12 GA potentially associated with immunotherapy (IO) benefit were similar in PDC and PAC and low in PNC. Low frequencies of MSI-High and low median TMB levels were similar in all 3 groups. Conclusions: The pathologic features of PDC, PAC and PNC have been classically maintained as representative of 3 different tumor types with potentially contrasting histogenesis. In the current CGP based study, all 3 tumor types did not display significant differences in genomic signatures other than the high RB1 GA. CGP may reveal biomarkers that could direct patients to targeted (PARP, MTOR and BRAF/MEK inhibitors) or immunotherapies ( CDK12 GA, MSI-High or high TMB status) especially in PDC and PAC. [Table: see text]

4533 Background: We performed a CGP to compare the genomic alterations (GA) in ABC, UBC and SCCB. Methods: 143 cases of ACB, 2,142 cases of UCB and 83 cases of SCCB were subjected to CGP using a hybrid-capture based assay. Tumor mutational burden (TMB) was determined on 1.1 Mbp of sequenced DNA and microsatellite instability (MSI) was determined on 114 loci. PD-L1 expression was determined by IHC. Results: ABC patients were younger and more often female than UBC and SCCB (P < 0.0001). UBC and SCCB had a higher GA/tumor than ABC (P = 0.01). Un-targetable GA were similar in all 3 groups involving TP53 and KRAS. APC GA were more frequent in ABC whereas TERT, CDKN2A/B and DNA-repair genes ( ARID1A and KDM6A) more frequently altered in UBC and SCCB. Targetable MTOR pathway GA ( PIK3CA, TSC1, PTEN) were more frequent in UBC and SCCB as were targetable kinase alterations ( FGFR3 and ERBB2). The UBC and SCCB had a significantly higher TMB than ABC (P < 0.0001) including mean TMB and TMB > 20 mut/Mb (P < 0.0001). CD274 (PD-L1) was amplified more frequently in SCCB than ACB or UBC (P < 0.0001). MSI high status was very uncommon in all tumor types. Conclusions: Deep sequencing reveals that ABC features a widely different genomic profile from UBC and SCCB. UBC has the highest frequencies of targetable kinase GA and high TMB. SCCB has the highest frequencies of IO efficacy predicting biomarkers including mean TMB and PD-L1 amp. Nonetheless, ABC does feature potential kinase targets such as FGFR3 and ERBB2. [Table: see text]

4585 Background: We compared the genomic alteration (GA) profiles of mCSCC, mPSCC and mSSCC to study impact on the targeted and immunotherapy options for the men and women suffering from these refractory cancers. Methods: 78 mPSCC, 604 mCSCC and 338 mSSCC underwent CGP using a hybrid-capture based assay. Tumor mutational burden (TMB) was determined on 1.1 Mbp of sequenced DNA and and microsatellite instability (MSI) was determined on 114 loci. Results: The HPV+/CDKN2A- status was significantly more frequent in the mCSCC than mPSCC or mSSCC (P < 0.0001). The GA/tumor frequencies were similar for mCSCC and mPSCC, but significantly higher in mSSCC (P < 0.0001). TP53 mutations were more common in mSSCC (UV light exposure) and mPSCC (likely due to loss of an original HPV+ status). TERT, NOTCH1 and FAT1 GA were more frequent in mPSCC and mSSCC whereas PIK3CA GA were more common in mCSCC. MTOR pathway targets (GA in STK11, FBXW7 and PTEN) were more common in mCSCC than mPSCC or mSSCC. MSI high status was extremely rare in all cases. TMB ≥ 10/20 mut/Mb frequencies were noteworthy in mPSCC and mCSCC but extraordinarily high in mSSCC. Examples of patients with mCSCC, mPSCC and mSSCC responding to targeted and immunotherapies will be presented. Conclusions: Although mCSCC, mPSCC and mSSCC share a variety of clinicopathologic features, the 3 tumor types can be sharply differentiated on CGP. The TP53, CDKN2A and HPV status of the tumor types differ significantly with HPV+ higher in the mCSCC group. There are opportunities for targeted therapies in all groups predominantly identified in the MTOR pathway. The relatively high numbers of cases with significantly elevated TMB in all 3 tumor types suggest that immunotherapies would be beneficial in a large subset of patients. [Table: see text]

4584 Background: We CGP to characterize the genomic alterations (GA) in MP and to enable the search for potential therapy targets. Methods: From a series of 201,766 consecutive clinical cases, 44 cases of clinically advanced MP underwent CGP using a hybrid-capture based commercial assay to evaluate all classes of GA. Tumor mutational burden (TMB) was determined on 1.1 Mbp of sequenced DNA and reported as mutations/Mb and microsatellite instability (MSI) was determined on 114 loci. PD-L1 expression was determined by IHC (DAKO 22C3 antibody). Results: All patients had clinically advanced recurrent and/or metastatic disease. 23 patients were females and 21 patients were males. There were 34 (77%) of MP known to have originated in the adrenal gland and 10 (23%) of the MP were sequenced from metastatic site where the exact primary site was unknown. The primary tumor was used for sequencing in 14 (32%) of the MP cases and a non-primary tumor metastatic site (liver, lung, bone, soft tissue, lymph node, kidney, peritoneal cavity, and chest wall) in 30 (68%) of the MP cases. There were 2.3 GA/tumor. The most frequent un-targetable GA were ATRX (25%), TP53 (21%), SDHB (13%), CTNNB1 (7%), VHL (7%), and CDKN2A/2B, PIK3R2, NOTCH2 and MEN1 (all 5%). The most frequent potentially targetable GA included RET (9%), NF1 (9%) and FGFR1 (5%). PBRM1 GA were found in 2% of MAP. Germline mutations in known cancer predisposition genes were predicted in 8 (18%) of cases involving SDHB (5 cases) and BRCA1, MEN1, and MSH2 (1 case each). The genomic signatures of primary MP were not significantly different from that obtained from sequencing of metastatic site biopsies. 0 (0%) of 5 MP stained positively for PD-L1 expression. The mean TMB was 2.95 mutations/Mb, the median TMB was 2.4 mutations/Mb. There 2 (5%) of MP with TMB ≥ 10 mutations/MB and 0 (0%) with TMB ≥ 20 mutations/Mb. 0 (0%) of 33 MP evaluated for MSI had a MSI-High status. Conclusions: Although the GA/tumor is relatively low for MP, CGP can reveal important potential therapy targets including RET, NF1 and FGFR1. MP do not reveal strong potential for immunotherapies with low TMB, absence of MSI-High status and low (2%) PBRM1 mutation frequencies.

552 Background: mPSCC is an aggressive malignancy with limited treatment options. Using CGP, we compared the therapy impacting genomic alterations (GA) between mPSCC and cutaneous mCSCC. Methods: DNA was extracted from 40 microns of FFPE samples from 78 cases of mPSCC and 338mCSCC.Comprehensive genomic profiling (CGP) was performed using a hybrid-capture, adaptor ligation based next generation sequencing assayto a mean coverage depth of > 500X. Tumor mutational burden (TMB) was determined on 1.1 Mbp of sequenced DNA and microsatellite instability (MSI) was determined on 114 loci. Results: mPSCC patients were younger than mCSCC (Table). Both tumors types feature high CDKN2A, TERT and FAT1 GA frequencies. NOTCH1 and PTCH1 GA are also more common in mCSCC than mPSCC. CD274 ( PD-L1) amplification was rare in both tumor types. Targeted therapy opportunities in mPSCC included alterations in kinase pathways ( EGFR GA in 6%; FGFR3 and ERBB2 GA in 4%); MTOR pathway ( NF1 GA in 7% and PTENGA in4%) and DNA repair pathway ( BRCA2and ATMGA in 7%). TMB was significantly higher in the UV light exposed mSCC than mPSCC with both tumor types having potential for responsiveness to immunotherapies. MSI-High status was extremely rare for both mPSCC and mCSCC. HPV viral DNA was identified in 29% on mPSCC but only in 5% of mCSCC. TP53 GA were significantly more frequent in HPV- than HPV+ mPSCC and mCSCC respectively (P < 0.0001 for both). Clinical outcomes of selected patients will be presented. Conclusions: mPSCC is a unique subtype of SCC with distinctive genomic features that contrast with those identified in mCSCC of non-penile UV light exposed skin. Given the potential opportunities for targeted therapies and immunotherapies that can be uncovered, continued study of CGP for the guidance of treatment for patients with mPSCC appears warranted.[Table: see text]

348 Background: We performed comprehensive genomic profiling (CGP) to learn whether sub-categorization of TMPRSS2 fusion status would impact therapy opportunities in patients with refractory CRPC and CRNEPC. Methods: DNA was extracted from 40 µm of FFPE sections of 2,424CRPC and 143 CRNEPC. CGP was performed on hybridization-captured, adaptor ligation-based libraries for up to 315 cancer-related genes. Tumor mutational burden (TMB) was determined on 1.1 Mbp of sequenced DNA and microsatellite instability (MSI) was determined on 114 loci. Results: The median ages for all 4 groups was similar (Table). TMPRSS2+( TMP+) CRPC features significantly greater TP53 and PTEN GA and TMPRSS2-( TMP-) CRPC featured higher MYC and ATM GA. Differences in BRCA2 and RB1 GA were not significant in the CRPC group. RB1 GA were more frequent in CRNEPC than CRPC. TP53 GA were higher in TMP+ CRNEPC than in TMP+ CRPC whereas GA in PTEN and MYC were similar in comparative groups. GA in AR and ATM were more frequent in CRPC than CRNEPC. The median TMB was higher in CRNEPC than CRPC and higher in TMP- than TMP+ tumors. TMP- CRPC and TMP- CRNEPC had higher TMB levelsthan TMP+ tumors in both groups. MSI-High status was more frequent in the TMP- CRPC and TMP- CRNEPC groups. Conclusions: For CRPC but not CRNEPC, the frequency of TMP+CRPC cases appears lower in advanced vsearly stage disease (TCGA data). CGP reveals significant differences in both targetable GA and markers of immunotherapy response between TMP+ and TMP- CRPC and CRNEC. Thus, when CRPC and CRNEPC areevaluated as to their TMPRSS2:ERG fusion status, significant genomic differences emerge which may impact therapy selection.[Table: see text]

640 Background: Collecting duct carcinoma (CDC) and renal medullary carcinoma (RMC) represent rare tumors that arise in the renal medulla are therapy resistant tumors that progress rapidly. Methods: DNA was extracted from 40 microns of FFPE specimen from refractory CDC (46 cases) and RMC (24 cases). CGPwas performed using a hybrid-capture, adaptor ligation based next generation sequencing assayto a mean coverage depth of > 800X. Tumor mutational burden (TMB) was calculated from a minimum of 1.11 Mb of sequenced DNA as previously described and reported as mutations/Mb. Microsatellite instability status (MSI) was determined on 114 loci. Results: All CDC patients were older and more frequently male (Table). Sickle cell trait was identified in both CDC and RMC, but far more frequently associated with RMC. All (100%) of CDC and RMC were clinically advanced Stage III and IV tumors with the primary tumor used for CGP in 70% of cases and a metastasis biopsy was sequenced in 30%. All (100%) CDC and RMC were intermediate (Grade 3) or high grade (Grade 4). In both tumor types, the GA/tumor was relatively low and there were no (0%) VHL GA. SMARCB1 GA were significantly more frequent in RMC than CDC but common in both tumors. Targeted therapies for kinase ( EGFR, RET) and MTOR ( NF2, TSC2) pathways were more frequent in CDC than RMC. At 1.8 mut/Mb, the median TMB was low for both tumor types with no (0%) of cases showing≥20 mut/Mb. No (0%) of the CDC or RMC cases featured MSI-high status. Conclusions: In addition to their histologic differences, the frequencies and types of GA seen in CDC differ significantly from that seen in RMC. The opportunities for biomarker driven targeted therapies for bothCDCand RMC appear limited with rare opportunities to target GA in TKGFR and MTOR pathways for CDC. Similarly, the relatively low TMB and absence of MSI-High status in CDC and RMCalso predicts that these tumors may be resistant to immunotherapies.[Table: see text]

565 Background: Although PSand NS testicular GCT have a favorable prognosis, on occasion these tumors can be refractory to conventional systemic treatments. Methods: FFPE tissues from 22 PS and 86 NSunderwent hybrid-capture based CGP to evaluate all classes of genomic alterations (GA). Tumor mutational burden (TMB) was determined on 1.1 Mbp of sequenced DNA and reported as mutations (mut) per megabase (Mb) and microsatellite instability (MSI) was determined on 114 loci. Results: PS patients were older than NS (P=0.007). The primary tumor was sequenced in 41% of PS and 18% of NS with a metastasis sample in 59% of PS and 82% of NS.Four (18%) of PS had syncytial trophoblast cells identified. The mean GA frequency at 4.1 mut/case for NS was higher than that seen in PS and this difference reached near significance (P=0.08). The KRAS, TP53, CCND2 and FGF6/23 GA frequencies were similar in both tumor types (Table). GA in KIT, PIK3CA/ MTOR, PTEN and BRCA2 were more frequent in PS than NS whereas BRAF and ERBB2 GA were more frequent in NS (Table). MSI-High status was absent in in PS (0%) and identified in 2% of NS. Higher levels of TMB were not encountered in PS (0% TMB ≥10 mut/Mb), but higher TMB levels were more frequent in NS (5% ≥ 10 mut/B and 1% ≥ 20 mut/Mb). Conclusions: The GA found in refractory PS and NS differ significantly. PS features a lower GA frequency with slightly higher potential for targeted therapies in kinase (KIT) and MTOR pathways but, has very low TMB predicting limited opportunities for immunotherapy for these patients. For NS targeted therapy biomarkers appear even more uncommon than seen in PS with only extremely rare kinase inhibitor opportunities. However, based on rare high TMB and MSI-High status, immunotherapies may be of benefit in a small subset of NS patients. Further study of genomic findings in relapsed and clinically aggressive PS and NS appears warranted. [Table: see text]

e16043 Background: Management of metastatic testicular cancer often requires post-chemotherapy resection of teratoma. This is well known and described in literature. However, the ability of teratoma to metastasize independently is not as well appreciated, making chemotherapy futile in patients with pure metastatic teratoma. Methods: 15 patients with metastatic teratoma were identified of which 13 had only teratoma in the orchiectomy and 2 had predominantly teratoma. All 15 had normal serum hCG and AFP. Cases were derived from a retrospective review of patients seen from 1989-2016. Results: Mean age of patients was 27 years. 12 patients presented initially with Stage II disease and 2 presented with stage III disease. Median RP mass size was 6 cm with a range of 1.5-24 cm. 2 of 15 patients were treated initially with a single course of chemotherapy with BEP and showed no response. The remaining 13 patients only received resection(s). All 15 patients underwent RPLND with 2 patients requiring additional mediastinal and retrocrural resection and 1 requiring lobectomy. All surgical specimens showed pure teratoma on pathology with no other active germ cells. Patients were followed for a median duration of 5 years and all 15 remain with no evidence of disease at most recent follow up. However, 1 patient needed subsequent surgery for a late relapse of teratoma and 1 patient had a second extra-gonadal primary. Conclusions: Teratoma can metastasize in the absence of other germ cells. Surgical treatment alone for patients with pure metastatic teratoma of any stage can result in cure for the majority of patients and this approach can help avoid unnecessary chemotherapy.