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PURPOSE: The COVID-19 pandemic has resulted in significant changes in health care delivery, including the rapid adoption of telemedicine across multiple specialties and practice environments. This includes postoperative visits (POV), despite limited data on outcomes following these telemedicine POV. We sought to determine whether these types of visits successfully identify and address postoperative complications when compared with in-person POV. METHODS: This was a retrospective cohort study of patients undergoing elective inpatient cancer-related surgery from March 2020 through December 2020. The exposure variable was type of POV (telemedicine v in-person). The primary outcome was unplanned hospital readmission within 90 days, and secondary outcomes included 30-day readmission, length of stay of first readmission, and mortality. RESULTS: Five-hundred thirty-five patients underwent elective inpatient operations and met our inclusion criteria. Of these, 98 (18.5%) had an initial telemedicine POV. There was no difference in 90-day readmission on the basis of POV type (16.3% telemedicine v 16.5% in-person, P = .99). Reasons for readmission did not differ between patients who underwent a telemedicine POV compared with in-person POV (all P > .05). After adjustment for patients' demographic and clinical factors, telemedicine POV was not associated with 90-day readmission (odds ratio, 0.89; 95% CI, 0.43 to 1.70; P = .77). CONCLUSION: Telemedicine POV use adopted during the COVID-19 pandemic did not increase risk of readmission when compared with in-person visits following inpatient oncologic surgery. These data can help inform policy on the continued use and application of telemedicine after the pandemic.

8557 Background: MPeM is a rare and aggressive cancer with very limited treatment options. Lack of dedicated research has impeded improvements in outcomes. Defining prevalent GAs is a critical unmet need for use of targeted therapies in these patients. Although MPeM is notably distinct from MPM vis-à-vis epidemiologic and clinical attributes, the genomic underpinings of these differences have yet to be established. We aimed at describing a comprehensive genomic profile (CGP) of MPeM in comparison to MPM. Methods: We performed a retrospective comparative analysis between 89 patients with MPeM and 241 patients with MPM (N = 330) who underwent CGP using CLIA certified next-generation sequencing assays. The cohort was generated using mesothelioma patients at MD Anderson Cancer Center (N = 223) and supplemented by additional mesothelioma patients (N = 107) from a publicly available database from Memorial Sloan Kettering Cancer Center, the MSK-IMPACT database. Essential clinicopathological variables were collected. Descriptive statistics, Fisher’s exact and Mann-Whitney tests were used for comparison. Kaplan-meier method and log rank tests were used for overall survival (OS) estimates. Results: MPeM cohort (vs. MPM) had more women (54% vs. 31%, P < 0.001) and younger age at diagnosis (56 vs. 69 years, P < 0.001). Histology was epithelioid, biphasic and sarcomatoid in 86%, 7% and 7% cases, a distribution similar to MPM cohort. At least 1 GA was found in 64 (72% vs. 82% in MPM, P = 0.044) of MPeM patients with a median of 1 (range 1 – 12) (vs. a median of 2, range 1 – 24, P < 0.001) GA per patient. A significantly lower proportion of MPeM patients had ≥ 3 mutations (14% vs. 26%, OR 2.1, P = 0.028) per patient. The most frequent mutations were present in the following genes: TP53 (24%), BAP1 (16%), NF2 (15%), MET (9%) and TRAF7, KIT and PIK3CA (each 6%). MPeM patients harbored more mutations in MET (9% vs. < 1%, P < 0.001) and TRAF7 (6% vs. < 1%, P = 0.02) but fewer mutations in BAP1 (16% vs. 32%, P = 0.003) and CDKN2B (0% vs. 5%, P = 0.041). The most common copy number variations (CNVs: amplifications or deletions) were seen in BAP1, MCL1, SETD2, WT1 (each 2%) and AURKA (1%) genes. Among genes with CNVs, MPeM had a lower rate of deletions in CDKN2A (1% vs. 6%, P = 0.040). Among more common GAs, only BAP1 mutations appeared to be associated with poor OS (45.7 vs. 127.1 months, HR 2.5, 95%CI: 0.6 – 10.1, P = 0.050) in patients with MPeM. Conclusions: In this large cohort with CGP, we identified potential molecular drivers in MPeM and demonstrated key genomic differences between MPeM and MPM. MPeM is frequently driven by GAs involved in cell cycle control, a potentially targetable pathway. Despite this insight from CGP, a large subset of patients do not have actionable GAs and for these patients, further collaborative trans-“omic” research efforts are needed to advance potential therapeutic options.

9013 Background: Malignant peritoneal mesothelioma (MPeM) is an orphan malignancy. No recommended/FDA approved therapies exist for salvage treatment beyond first-line platinum and pemetrexed based chemotherapy. While immune checkpoint inhibition has shown preliminary efficacy in mesotheliomas, data and efficacy is limited in MPeM patients (pts) [objective response rate (ORR) ~ 11%; median progression-free survival (mPFS) ~ 4 months (m); median overall survival (mOS) ~ 11 m]. We aimed to prospectively assess the safety and efficacy of combined anti-PD1 (atezolizumab) and VEGF (bevacizumab) blockade (AtezoBev) in pts with MPeM. Methods: In this phase 2 study, eligible pts with histologically confirmed MPeM, ECOG PS 0-1, and prior platinum and pemetrexed treatment were treated with 1200 mg of atezolizumab and 15 mg/kg of bevacizumab IV every 21 days until disease progression, unacceptable toxicity, or withdrawal. Primary endpoint was confirmed ORR by RECIST 1.1 by independent radiology review. Duration of response (DOR), PFS and OS were pre-specified secondary endpoints. Results: Among 20 enrolled pts (3/2017 - 2/2019), median age was 63 (range, 33-87) years, 12 (60%) were female, 12 (60%) had PS 0, and 2 (10%) had biphasic MPeM. Among 20 evaluable pts (median cycles 14), confirmed ORR was 35% (7 pts; 95% CI: 15.4-59.2) (median DOR 8.8 m). Responses were ongoing in 5/7 (71.4%) pts at data cutoff. The median follow-up was 20.5 months. Six deaths were observed during follow-up, and the 1-year OS was 79% (95% CI: 52 – 91) (median OS ~ NR). Median PFS was estimated as 17.6 m (95% CI: 9.1 – NR). The 1-year PFS was 54% (95% CI: 28 – 74). Grade 3 (no grade 4/5) treatment-emergent adverse events occurred in 10 (50%) pts; most common being hypertension (40%) and anemia (10%). Two (10%) pts had grade 3 immune-related adverse events. Translational studies are ongoing. Conclusions: AtezoBev showed promising and durable efficacy in relapsed/refractory MPeM with acceptable safety profile. Ongoing multiomic analyses of pre and on-treatment tissue/liquid biopsies obtained on all these pts will provide additional insight into mechanisms and biomarkers of response and resistance. Clinical trial information: NCT03074513.