Bhatia S, Nghiem P, Veeranki SP, Vanegas A, Lachance K, Tachiki L, Chiu K, Boller E, Bharmal M. Real-world clinical outcomes among patients with advanced Merkel cell carcinoma treated with avelumab in academic medical centers in the United States. Presented at the 2022 2nd International Symposium on Merkel Cell Carcinoma; April 25, 2022. Seattle, WA. Previously presented at the SITC 2021 36th Anniversary Annual Meeting.

BACKGROUND AND AIMS: In March 2017, avelumab (anti–PD-L1) was approved for the treatment of metastatic MCC and has demonstrated meaningful survival benefit and durable response. We sought to investigate real-world clinical outcomes of avelumab-treated patients with aMCC (stage IIIB/IV) in US academic medical centers.

METHODS: A retrospective chart review study of patients with aMCC who initiated avelumab between March 1, 2017, and July 31, 2019 was conducted at 6 US academic medical centers across the 4 census regions. Eligible patients were followed through December 30, 2020. Descriptive analyses were conducted for demographics, clinical characteristics, and outcomes. Kaplan-Meier curves were constructed for real-world duration of response (rwDOR), real-world progression-free survival (rwPFS), overall survival (OS), and time-to-treatment discontinuation.

RESULTS: Ninety patients with aMCC received avelumab; median follow-up was 15.0 months (95% CI, 13.1-17.8). Median age was 68 years; most were male (58%) and White (93%). At avelumab initiation, 74 and 16 patients had stage IV and IIIB MCC, respectively. Primary tumor was most commonly on the lower limb (38%), with metastasis primarily to lymph nodes (67%) and lung (52%); 52% had visceral metastases. Approximately 42% and 26% had an ECOG PS of 2 and 3, respectively. Median duration of avelumab treatment was 13.5 months (95% CI, 6.4-30.6); 58% discontinued by end of follow-up. Avelumab-treated patients (n=90) had a real-world objective response rate (rwORR) of 73% (95% CI, 64-83), median rwPFS of 24.4 months (95% CI, 8.3-not reached [NR]), and median OS of 30.7 months (95% CI, 11.2-NR). Seventy-three patients (81%) received avelumab as first-line treatment and 17 (19%) as second-line or later; in these subgroups, rwORR (95% CI) was 75% (65-85) and 65% (39-90), respectively, median rwDOR (95% CI) was NR (NR) and 4.6 months (1.1-NR), median rwPFS (95% CI) was 36.1 months (9.3-NR) and 6.4 months (4.5-NR), and median OS (95% CI) was 41.7 months (10.2-NR) and 15.9 months (4.3-NR).Outcomes by stage at avelumab initiation will also be reported.

CONCLUSIONS: This real-world study of avelumab-treated patients with aMCC demonstrates high rwORR with durable responses and prolonged survival. Findings are consistent with results from pivotal clinical trials and recent observational studies.

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