Panattoni, Laura

e16042 Background: Current second-line (2L) therapies for patients (pts) with advanced/metastatic esophageal squamous cell carcinoma (adv/met ESCC), including docetaxel, paclitaxel and irinotecan, have demonstrated modest survival gains. The National Comprehensive Cancer Network added the use of anti-programmed cell death protein-1 (PD-1) therapies (e.g., pembrolizumab, nivolumab) in the 2L to their guidelines in 2020. A real-world evidence study of 2L therapy for adv/met ESCC patients reported a median (95% CI) overall survival (OS) of 201 (153-249) days but did not include recently approved anti-PD-1 agents. Other studies of 2L anti-PD-1 therapy relied on claims data without the ability to report survival. Limited studies exist for 2L ESCC real-world treatment patterns. Herein, we characterize the real-world treatment patterns and OS for a recent cohort of US pts initiating an anti-PD-1 2L therapy. Methods: Pts (≥ 18 years of age) from the United States diagnosed with adv/met ESCC and initiating an anti-PD-1 2L therapy between January 1, 2011 and February 28, 2021 were selected using the electronic health record (EHR)-derived de-identified Flatiron Health database. Pt characteristics and descriptive treatment patterns were reported. Duration of therapy (DoT; start of therapy until last administration) was computed and OS (start of therapy until death or last recorded medical activity) was estimated by the Kaplan Meier method. Results: 60 pts were included who initiated an anti-PD-1 2L therapy. At 2L initiation, the median age was 66 years, 65% were male, 53% were white, 82% had a history of smoking, and 53% had stage IV disease. The median DoT was 92 days and median OS was 303 days with variability across agents (Table) . Of the 60 pts, a total of 21 (35%) initiated 3L therapy (8 initiated an anti-PD-1; 13 initiated a non-anti-PD-1). Of the 39 (65%) pts who did not initiate a 3L therapy, 16 (41%) died within 60 days of the final 2L administration, 12 (31%) lacked 60 days of follow-up observation, and the remaining 11 (28%) patients had no further 2L treatment. Conclusions: Compared to prior real-world analyses, use of anti-PD-1 therapy in the 2L for patients with advanced/metastatic ESCC may be associated with survival gains over other approved non-anti-PD-1 therapies. However, future real-world studies are needed to directly compare PD-1 inhibitors with other 2L therapies.[Table: see text]