Chemoradiotherapy and Subsequent Immunochemotherapy as Conversion Therapy in Unresectable Locally Advanced Esophageal Squamous Cell Carcinoma: A Phase II NEXUS-1 Trial

PURPOSE: This phase II trial investigated the safety and efficacy of chemoradiotherapy (CRT) followed by immunochemotherapy (iCT) and surgery in unresectable locally advanced esophageal squamous cell carcinoma (ESCC). PATIENTS AND METHODS: Patients with unresectable locally advanced ESCC received radiotherapy (50 Gy/25f, 5 days/week) and nab-paclitaxel (100 mg on day 1/week) plus cisplatin (25 mg/m2 on day 1/week) for 5 weeks, followed by tislelizumab (200 mg on day 1/cycle) plus chemotherapy (nab-paclitaxel 150 mg/m2 and cisplatin 75 mg/m2 on day 2/cycle) for two 21-day cycles. Patients who converted to resectable underwent surgery 2 to 4 weeks afterward. The primary endpoint was a 1-year progression-free survival (PFS) rate. RESULTS: Thirty patients were enrolled and underwent CRT (median follow-up: 21 months), of whom 24 received iCT. Twenty (66.7%) patients achieved resectability (R0: 95.2%; pathologic complete response: 65.0%; major pathologic response: 90.0%). One-year PFS and overall survival (OS) rates were 79.4% and 89.6%, respectively. The R0 resection group exhibited longer PFS (median, not reached vs. 8.4 months; HR = 0.28; 95% confidence interval, 0.08-0.84; P = 0.02) and OS (median, not reached vs. 19.2 months; HR = 0.18; 95% confidence interval, 0.04-0.73; P < 0.01) than the nonsurgery group. Grade 3 to 4 adverse events were observed in 11 (11/30, 36.7%) patients, and immune-related pneumonitis was observed in 5 (5/24, 20.8%) patients. Post-CRT minimal residual disease before surgery was associated with unfavorable PFS and OS. CONCLUSIONS: Our study met the primary endpoint. Conversion CRT and subsequent iCT followed by surgery was a promising treatment strategy for unresectable locally advanced ESCC.