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103 Background: Novel strategies to improve the efficacy of immune checkpoint inhibitors in microsatellite stable (MSS) mCRC are needed. CV301 is a vector-based vaccine that expresses carcinoembryonic antigen (CEA) and mucin 1 (MUC1), and in a phase II study in resected hepatic limited mCRC significantly improved OS compared with unvaccinated contemporary controls. Methods: In this multi-center randomized phase II study, patients with previously untreated resectable hepatic-limited mCRC were randomized to perioperative nivolumab + mFOLFOX +/- CV301 (Arm B) with a primary endpoint of 3-year OS. Treatment included mFOLFOX-nivo (+/- CV) x 4 cycles followed by resection, then 8 more cycles of mFOLFOX-nivo followed by maintenance nivo monthly for two years in both arms, and CV boosters concurrently with mFOLFOX, and then every 3 months for two years in arm B. Secondary endpoints of ORR (following induction pre-resection), PRR, and safety were determined. Correlative analyses included immune cell quantification using Immunoscore and T-cell clonality. Results: 17 patients were enrolled prior to premature closure for slow accrual (8 arm A, 9 arm B). At the time of data cutoff, 5 patients remained on treatment and no deaths had occurred. One patient was removed from study due to protocol non-compliance. The median age was 61, majority were male (59% vs 41%), and ECOG PS 0-1 (71% 0, 17% 1). All patients had complete surgical resection. Four patients (24%) experienced a SAE related to drug. The TRAE rate was 40.3%,. No AEs delayed/prevented surgical resection. The ORR in arm A was 50% (including 4 CR) and 87.5% in arm B (including 7 CR) (p=0.129, NS). There was no significant difference in pathologic response (p=0.9047). Correlative analyses demonstrated the Immunoscore CD3/CD8 predicted response to mFOLFOX + nivolumab, but did not correlate with response to CV301, though CV301 may induce a shift to predominantly cytotoxic CD8+ T cells. While there was no significant difference in T cell repertoire, clonality, fraction (TCFr) or richness, patients in arm B had significant decreases in blood TCFr and increase in tumor TCFr with treatment; those with CR had higher TCFr and clonality. Conclusions: The addition of CV301 to perioperative nivolumab and mFOLFOX was safe, did not delay or prevent surgical resection, and gave a higher response (p=ns due to sample size). Changes in T cells suggest a vaccine response. Clinical trial information: NCT03547999 . [Table: see text]

144 Background: TAS-102 (trifluridine/tipiracil) is a novel oral antimetabolite for late line metastatic colorectal cancer (CRC) approved in 2018. Many patients are treated early in their course with oxaliplatin (OX), particularly adjuvant, and may benefit from re-treatment. In this trial we combine the typical late line use of TAS with OX (BEV [bevacizumab] added at investigator discretion) with goal of improved response. Methods: Eligibility included measurable CRC previously treated with all approved drugs per TAS package insert (irinotecan, oxaliplatin, 5FU, anti-VEGF, anti-EGF) as appropriate, PS = 0-1, labs within usual range, neuropathy < grade 2, ability to take oral meds, appropriate contraception. If no contraindication to BEV, this could be added at patient. TAS was dosed at 35 mg/m2 days 1-5 with OX 85/m2 d1 every 14 days (and BEV 5 mg/kg, if given). All supportive care was allowed including growth factors. Results: 47 patients (pts, median age 55) were enrolled in a Simon mini-max design, including 45% female, 21% black, 11% Asian, 11% Hispanic and 5% mixed. 26 pts received BEV. For the first 40 pts, 385 cycles were given (mean = 7 cycles, median 8) with 18 pts (45%) requiring dose reductions (1 dose reduction = 9 pts, 2 = 6, 3 = 3), and 9 receiving (peg)/filgrastim. Toxicities leading to SAEs included gr 3 heme (2), heart failure, abd pain/n/v (6), sepsis (2), urinary (4); and related gr 3 included one gr 3 vomiting and one gr 3 neutropenia. Independently reviewed RECIST Response (N = 32) included PR 2(6%), SD 23 (72%), PD 7 (22%). Mean TTP was 4.5 m (median 4, range 1 – 18) with 9 (28%) pts more than 6 months. Conclusions: In patients with late-line CRC and candidates for TAS (trifluridine/tipiracil), treatment with TAS plus OX is both well tolerated and active. RR is higher than single agent and 78% (95% CI, 60-91%) of patients had stable disease or response, with 60% receiving 8 or more cycles. Randomized trials comparing to single agent TAS are warranted in this setting. Clinical trial information: NCT04294264 .

3521 Background: Response to antiPD-1 monotherapy is poor in patients (pts) with advanced microsatellite stable (MSS)/mismatch-repair proficient (pMMR) CRC. Combination of chemotherapy with antiPD-1 pembro may potentiate the antitumor immune response and provide greater antitumor activity than either agent alone. Combination of pembro and mFOLFOX7 or FOLFIRI in the ongoing phase 1b multicohort KEYNOTE-651 (NCT03374254) study in metastatic MSS/pMMR CRC showed antitumor activity. We present results with approximately 20 mo of additional follow-up. Methods: Pts had metastatic MSS/pMMR CRC and were previously untreated (cohort B) or received 1 prior line including a fluoropyrimidine + oxaliplatin (cohort D). Pts received pembro 200 mg Q3W + mFOLFOX7 Q2W (cohort B) or pembro 200 mg Q3W + FOLFIRI Q2W (cohort D). Primary end points were safety (DLT) and RP2D. Secondary end point was ORR per RECIST v1.1 by investigator review. DOR, DCR, and PFS per RECIST v1.1, and OS were exploratory end points. Results: Median study follow-up (range) at data cutoff (Oct 15, 2021) was 30.2 mo (25.0-43.6) for cohort B (n = 31) and 33.5 mo (25.2-43.2) for cohort D (n = 32). Treatment was discontinued in 29 pts (94%) in cohort B and 28 pts (88%) in cohort D, mostly because of PD (61% and 66%, respectively). At prior analysis (Feb 10, 2020), RP2D was confirmed as the starting dose in both cohorts; no new DLT had occurred. In cohort B, gr 3/4 TRAEs occurred in 18 pts (58%), most commonly neutropenia and decreased neutrophil count (both n = 5; 16%); 19 pts (61%) discontinued drug because of a TRAE. In cohort D, gr 3/4 TRAEs occurred in 17 pts (53%), most commonly, neutropenia (n = 7; 22%), diarrhea and fatigue (both n = 4; 13%); 3 pts (9%) discontinued drug because of a TRAE. There were no gr 5 TRAEs in either cohort. Efficacy by cohort and KRAS mutation status are below (Table). PD-L1 data and DNA/RNA-based biomarker data including GEP, consensus signatures, TMB, and LoF mutations will be included in the presentation. Conclusions: After 2.5 y of follow-up, the combination of pembro with either mFOLFOX7 or FOLFIRI continued to demonstrate a manageable safety profile with no new safety signals. Efficacy data from these single-arm cohorts appear comparable to historical data for current SOC. Clinical trial information: NCT03374254. [Table: see text]

3573 Background: Response to antiPD-1 monotherapy is poor in microsatellite stable (MSS)/mismatch-repair proficient (pMMR) mCRC; the combination of antiPD-1 pembro + anti-MEK bini, with or without chemo, may improve upon this limited response. KEYNOTE-651 (NCT03374254) is an open-label phase 1b multicenter trial of pembro + bini (cohort A) or pembro + bini + chemo (mFOLFOX7 in cohort C, FOLFIRI in cohort E) in MSS/pMMR mCRC. Preliminary results from the dose-finding phase at 2 dose levels (DL) of bini are presented. Methods: Patients (pts) had MSS/pMMR mCRC and must have been previously treated with fluoropyrimidine, irinotecan, and oxaliplatin in cohort A, or with fluoropyrimidine + oxaliplatin-based regimen in cohort E; pts were previously untreated in cohort C. Pts received pembro 200 mg Q3W + bini 30 mg BID (cohort A, DL1), pembro 200 mg Q3W+ bini 30 mg BID + mFOLFOX7 Q2W (cohort C, DL1) or pembro 200 mg Q3W + bini 30 mg BID + FOLFIRI Q2W (cohort E, DL1). Bini dose escalation to 45 mg BID (DL2) was planned in cohorts A, C, and E, with a target dose-limiting toxicity (DLT) of 30%. Primary end point was safety (DLT). Secondary end point was ORR. DCR, PFS, and OS were exploratory. ORR, DCR, and PFS were assessed by investigator per RECIST v1.1. Results: Median study follow-up at data cutoff (Oct 15, 2021) was 36 mo (range, 32-43) for cohort A, 17 mo (2-24) for cohort C, and 11 mo (2-25) for cohort E. In cohort A, 1/6 pts (17%) had DLT at DL1; no DLT occurred in 14 pts (0%) at DL2. In cohort A, gr 3/4 TRAEs occurred in 3/6 pts (50%) at DL1 and 8/14 pts (57%) at DL2. In cohort C, 3/9 evaluable pts (33%) had DLT at DL1; thus, bini dose was not escalated to DL2. In cohort C, gr 3/4 TRAEs occurred in 9/11 total pts (82%). In cohort E, 1/5 evaluable pts (20%) had DLT at DL1 and 5/10 evaluable pts (50%) had DLT at DL2. Enrollment was stopped in cohort E, DL2 and bini dose was de-escalated to DL1; 2/4 additional pts (50%) had DLT at DL1 (total 3/9 pts [33%] had DLT in cohort E, DL1). In cohort E, gr 3/4 TRAEs occurred in 5/9 pts (56%) at DL1 and 10/11 total pts (91%) at DL2. No gr 5 TRAEs occurred in any cohort. ORR was 0% in cohort A; limited efficacy was seen in cohorts C and E (Table). Conclusions: Bini could be safely combined with pembro in cohort A. However, with bini + pembro + chemo, the 45-mg dose of bini was not well tolerated and required dose reduction to 30 mg. Addition of bini to pembro + chemo did not improve efficacy; therefore, enrollment was prematurely closed in cohorts C and E. Efficacy by KRAS mutation status will be shown. Clinical trial information: NCT03374254. [Table: see text]

e15587 Background: For resected stage II MSI-high (MSI-H) colorectal cancer (CRC) without high-risk features (HRF), standard of care recommendation per NCCN guidelines is observation. For tumors with HRF, the prognostic significance and impact of adjuvant therapy remains uncertain. The NCDB was queried to assess outcomes. Methods: Adult patients with stage II MSI-H CRC, surgically resected between 2010 and 2017, were identified in the NCDB. Univariate and multivariate Cox proportional hazards models and Kaplan Meier survival curves were generated to assess impact of HRF, clinical and demographic variables, and chemotherapy use on overall survival (OS). Results: 9634 patients with stage II MSI-H CRC who met criteria were identified. In multivariate analysis T4 tumor status, < 12 lymph nodes (LN) examined, perineural invasion (PNI) and positive margins were associated with worse OS, as were older age and increased comorbidity index (CDCC). Poor differentiation and lymphovascular invasion (LVI) were not associated with OS. No OS difference was observed between T4a vs T4b tumors or based upon tumor sidedness, tumor size, or sex. Excluding poor differentiation (33%) and LVI (17%), HRFs were present in 26% of cases: 21% (n = 2033) had 1 HRF and 5% (n = 505) had > 1 HRF. HRFs were associated with decreased 5-year OS. For 1 HRF OS was 66% (HR 1.48, p < 0.0001) and for > 1 HRF OS was 54% (HR 2.31, p < .0001), compared to 77% with 0 HRFs. HRF presence was associated with increased chemotherapy use: 46% for > 1 HRF, 26% for 1 HRF, and 8% with 0 HRFs. pT4 tumors (T4b > T4a) and younger age were also associated with increased chemotherapy use. By age group, chemotherapy was utilized in 31% of those < 50, 27% of those 51-60, 17% of those 61-70 and 6% of those > 70 years old. In the overall population, chemotherapy administration was associated with improved OS on multivariate analysis compared with no treatment (N = 1344; HR 0.76, p < 0.0001). 69% of patients received multi-agent chemotherapy. However, survival was similar between those receiving single-agent vs multi-agent chemotherapy (HR 1.2, p = 0.2016). In patients < 60 years old, chemotherapy use was associated with decreased OS (HR 1.4, p = 0.0156). Conclusions: In this retrospective, uncontrolled large database survey, HRFs are associated with decreased OS in stage II MSI-H CRC. This data indicates that poor differentiation and LVI do not independently worsen outcomes, but that the presence of multiple HRFs bears relevance. Though chemotherapy was associated with improved OS, the association is reversed in the < 60 year old population; this analysis cannot fully control for extent of disease and PS, among other factors. Chemotherapy should be judiciously administered in Stage II MSI-H CRC with HRFs. Immunotherapy trials are justified.[Table: see text]

11002 Background: Gender disparity is an important issue in medicine, as women occupy a minority of academic leadership positions despite increased representation in the physician workforce. One important aspect is the gender gap of speakers at academic meetings, which limits opportunities for career advancement and mentorship. This underrepresentation of women is largely anecdotal in oncology. We hypothesized that original research is less frequently presented by women at the annual ASCO meeting. We sought to examine presentation patterns from recently featured ASCO speakers, categorized by presentation type and gender. Methods: We conducted a retrospective, observational review of data from the 2018-2021 ASCO annual meetings. Mixed-gender coders extracted data from the ASCO Annual Meeting library and institutional public websites. Speaker-identified gender was unavailable; binary gender was determined by presenter name, pronouns, and video files. For original research, we collected data on last authors as well as these roles are also considered meritorious. Cochran–Mantel–Haenszel tests were used to investigate the association of gender and roles adjusted for each stratification variable individually. Common odds ratios (ORs) were estimated for each association. Breslow-Day Tests were used to test the homogeneity of these ORs among the different levels of each stratification variable. No adjustments for multiple testing were used. Results: We reviewed 4267 unique presentations, including those which highlighted original research (Poster Discussion, Oral Abstract, Clinical Science Symposium, Plenary) vs. education (Case-Based Panel, Education Sessions, Highlights of the Day). For original research, women were significantly more likely to have an ASCO-appointed role (discussant, speaker, or chair) than a first or last author role (48% vs. 32.7% of presentations, p < 0.0001), even after adjusting for conference year (OR 0.53, 95% CI: 0.45-0.61), session type (0.52, 0.45-0.61), degree (0.50, 0.43-0.58), academic rank (0.55, 0.47-0.64), and geographic region (0.58, 0.50-0.68). There was no difference between in-person and virtual conferences (p = 0.584). For education sessions, women comprised 46.1% (n = 626), nearly half, of these speaking roles (all ASCO-appointed) compared with men. 38% of the data was independently re-reviewed to confirm accuracy; 96.4% concordance was observed in presenter gender. Conclusions: Women are less likely to present highlighted original research and are more likely to have an appointed educational role at ASCO annual meetings. This likely reflects broader gender disparity within academia. Future analyses could be improved by examining speaker-identified gender. As high-profile original research can elevate careers, examining factors contributing to this observed disparity may reveal important approaches to address gender leadership gaps in oncology.

TPS493 Background: Both the incidence and death rate of hepatocellular carcinoma (HCC) are on the rise in the United States, and overall, the prognosis is grim. First-line treatment options for patients with advanced disease previously included tyrosine kinase inhibitors (TKIs) which have resulted in a median overall survival (OS) of less than a year. Combinations of immune checkpoint inhibitors (CPIs) with vascular endothelial growth factor (VEGFR) inhibitors are of interest given the known effects of VEGF in the tumor microenvironment, including promoting inhibitory immune cells, suppressing maturation of dendritic cells, decreasing cytotoxic T cell responses, and altering lymphocyte development and trafficking. The phase III IMbrave150 trial investigated the combination of atezolizumab (A) and bevacizumab (B) as compared to sorafenib (S) in previously untreated locally advanced or metastatic HCC patients, and resulted in significantly improved OS (mOS: 19.2 mos AB vs 13.4 mos S), PFS (mPFS: 6.9 mos AB vs 4.3 mos S), and response rates (ORR: 29.8% AB vs 11.3% S), and a meaningful improvement in duration of response (mDOR: 18.1 mos AB vs 14.9 mos S). Notably, patients with class Child-Pugh B liver dysfunction were excluded from this study, although they are clinically abundant. We hypothesize the combination of AB will be safe and well tolerated in patients with locally advanced or metastatic HCC with Child-Pugh class B7 liver dysfunction. In addition, we expect efficacy will be similar to that demonstrated by the IMbrave150 study, and that ctDNA will correlate with, and possibly predict, clinical outcomes. Methods: This will be a single arm phase II study investigating the safety of the combination of AB in patients with previously untreated locally advanced or metastatic HCC with Child-Pugh B7 liver dysfunction. Patients must also be ECOG PS 0-1 and without clinically significant ascites or hepatic encephalopathy, untreated esophageal/gastric varices (assessed by EGD within the prior 6 months), or recent significant bleeding. We will enroll 50 patients with the primary endpoint of grade 3-5 treatment-related adverse event rate by CTCAE v5. Secondary endpoints include ORR, disease control rate (DCR), DOR, progression free survival (PFS), and OS. Correlative studies include tumor molecular signature by next generation sequencing (NGS) tissue analysis and ctDNA levels to correlate both with each other and with clinical benefit. Patients will receive A 1,200 mg IV and B 15 mg/kg IV every 3 weeks until disease progression or intolerable toxicity. Tumor imaging reassessment will occur every 3 cycles. Archival or fresh tumor biopsy will be required at baseline, and plasma for ctDNA will be collected with each imaging reassessment. The trial is being conducted at sites throughout the Big Ten Cancer Research Consortium (Big Ten CRC) and is currently screening eligible subjects (NCT04829383). Clinical trial information: NCT04829383.