Adjuvant chemoradiotherapy plus pembrolizumab for locally advanced esophageal squamous cell carcinoma with high risk of recurrence following neoadjuvant chemoradiotherapy: a single-arm phase II study

Adjuvant nivolumab reduces recurrence in patients with locoregional esophageal cancer who had pathological residual disease after neoadjuvant chemoradiotherapy and R0 resection. However, the efficacy of adjuvant anti-PD-1 therapy in patients at higher risk of recurrence remains unclear.

This phase II trial (ClinicalTrials.gov identifier: NCT03322267) enrolled patients with locally advanced esophageal squamous cell carcinoma (ESCC) received neoadjuvant chemoradiotherapy plus esophagectomy but still had various risk factors for recurrence, such as involved or close margins (≤ 1 mm), extranodal extension of the involved lymph nodes, and the ypN2-3 stage. Patients received adjuvant therapy composed of a course of cisplatin-based chemoradiotherapy and pembrolizumab (200 mg, IV every 3 weeks) for 18 cycles. The primary endpoint was 1-year relapse-free survival (RFS) rate.

Twenty-five patients were enrolled. The risk factors were tumor margins of ≤ 1 mm (18 patients), extranodal extension of the involved lymph nodes (9 patients), and the ypN2-3 stage (9 patients). The median follow-up duration was 21.6 months (95% CI: 18.7–33.2). The rate of 1-year RFS was 60.0%. The median duration of RFS and overall survival was 14.3 (95% CI: 9.0–19.5) and 21.6 (95% CI: 0.0–45.5) months, respectively. Treatment-emergent adverse events of any grade and those of ≥ 3 grade occurred in 56% and 8% of all patients receiving cisplatin-based chemoradiotherapy and in 79.2% and 12.5% of those receiving pembrolizumab.

Adjuvant chemoradiotherapy followed by pembrolizumab is feasible and may be associated with improved 1-year RFS rate in patients at high risk of recurrence after trimodality therapy for locally advanced ESCC.