Neoadjuvant sintilimab and chemotherapy in patients with potentially resectable esophageal squamous cell carcinoma (KEEP-G 03): an open-label, single-arm, phase 2 trial.

Background: The standard neoadjuvant treatments in patients with esophageal squamous cell carcinoma (ESCC) still have either poor safety or efficacy. Better therapies are needed in China.

Methods: This was an open-label, single-arm, phase 2 trial. Patients with potentially resectable ESCC (cT1b-3, Nany, M0 or T4a, N0-1, or M0) received preoperative intravenous sintilimab plus triplet chemotherapy (liposomal paclitaxel, cisplatin, and S-1) every 3 weeks for two cycles. The primary endpoints were safety and surgical feasibility; the secondary endpoint was major pathological response (MPR) rate. Genomic biomarkers (genetic mutations, tumor mutational burden (TMB), circulating tumor DNA status and immune microenvironment) in baseline tumor samples were investigated.

Results: All 30 patients completed two cycles of neoadjuvant treatment and underwent surgical resection. Grade 3-4 treatment-related adverse events (TRAEs) occurred in 36.7% (11/30) of patients. The most frequent TRAEs were decreased white cell count (76.7%), anemia (76.7%), and decreased neutrophil count (73.3%). All TRAEs were hematological toxicities; none caused ≥30 days surgical delay. The MPR and pathological complete response (pCR) rates were 50.0% (15/30; 95% CI 33.2 to 66.9) and 20.0% (6/30; 95% CI 9.5 to 37.3), respectively. Patients with higher TMB and more clonal mutations were more likely to respond. ERBB2 alterations and ctDNA high-releaser status have a negative correlation with neoadjuvant ICI response. No significant difference was observed between therapeutic response and tumor immune microenvironment.

Conclusions: Neoadjuvant sintilimab plus platinum-based triplet chemotherapy appeared safe and feasible, did not delay surgery and induced a pCR rate of 20.0% in patients with potentially resectable ESCC.

Trial Registration Number: NCT03946969.