Efficacy of irinotecan-based chemotherapy after exposure to an anti-PD-1 antibody in patients with advanced esophageal squamous cell carcinoma

Objective: Several anti-programmed cell death 1(anti-PD-1) antibodies have demonstrated potential efficacy in the treatment of advanced esophageal squamous cell cancer(ESCC). However, the response to subsequent chemotherapy after the failure of PD-1 blockade in ESCC patients has not been reported, and the optimal sequencing of immunotherapy and chemotherapy remains controversial. The aim of the present study was to evaluate responses to irinotecan-based subsequent chemotherapy in advanced ESCC patients who had progressed after treatment with camrelizumab(SHR-1210), a novel anti-PD-1 antibody.Methods: We retrospectively reviewed the medical records of patients with advanced ESCC treated with camrelizumab at a single institution. Consecutive patients who received subsequent irinotecan-based chemotherapy were selected for data collection and analysis.Results: Overall, a total of 28 patients were included. All patients had received at least two lines of systemic treatment prior to irinotecan salvage. The most common regimen that was administered after PD-1 blockade was irinotecan in combination with 5-fluorouracil(5-Fu)(or its derivatives), which was given to 19 patients. The objective response rate(ORR) and disease control rate(DCR) were 17.9%(5/28) and 64.3%(18/28), respectively,with 5(17.9%) patients achieving a partial response and 13(46.4%) having stable disease. The median progressionfree survival(PFS) was 3.18 [95% confidence interval(95% CI), 2.48-3.88] months and the median overall survival(OS) was 6.23(95% CI, 4.71-7.75) months. No new safety issues, either immune-related or otherwise, were observed.Conclusions: Our results suggested that the response to irinotecan-based chemotherapy after PD-1 blockade in advanced ESCC patients appeared similar to that previously observed in patients who had not received PD-1 antibodies, and further study in larger cohorts or randomized trials is warranted to verify our observation.