Phase II Trial of Adjuvant S-1 Following Neoadjuvant Chemotherapy and Surgery in Patients with Locally Advanced...

Neoadjuvant chemotherapy followed by surgery (NAC-S) is the standard therapy for locally advanced esophageal squamous cell carcinoma (ESCC) in Japan.

The aim of this phase II trial was to assess the efficacy and safety of the addition of adjuvant S-1 after R0 resection in ESCC patients who received NAC-S.

Key eligibility criteria included clinical stage IB-III (without T4 disease) ESCC, age 20-75 years, and an Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1. Patients received adjuvant therapy with four cycles of S-1 (80 mg/m²/day) administered orally for 4 weeks of 6-week cycles. The primary endpoint was 3 year relapse-free survival (RFS). If the lower confidence limit for 3 year RFS was >50%, we judged that the primary endpoint of this study was met.

A total of 52 patients were enrolled between January 2016 and January 2019. Two patients were excluded from analysis; five patients were determined to have R1 or R2 resection, and seven patients did not receive adjuvant S-1. The 3-year RFS and overall survival rates in the intention-to-treat population were 72.3% (90% confidence interval [CI] 59.9-81.5) and 85.0% (90% CI 73.9-91.6), indicating that the primary endpoint was met. Grade ≥3 adverse events with an incidence ≥10% included neutropenia (13.2%), anorexia (13.2%), and diarrhea (10.5%). There were no treatment-related deaths.

Adjuvant S-1 after NAC-S showed promising efficacy with a manageable safety profile for patients with resectable ESCC and warrants further evaluation in larger studies.