Failure patterns and the value of postoperative adjuvant radiotherapy in esophageal squamous cell carcinoma patients treated with neoadjuvant immunotherapy combined with chemotherapy.

e16151 Background: Neoadjuvant immunotherapy combined with chemotherapy followed by surgery (NICT+S) has shown favorable pathological complete response (pCR) rates and prognosis in esophageal squamous cell carcinoma (ESCC), but failure patterns and the benefits of postoperative adjuvant radiotherapy (PORT) in non-pCR patients remain unclear. Methods: A retrospective analysis assesses failure patterns, Cox regression between radiotherapy (RT) and non-radiotherapy (NRT) groups before and after PSM, and safety evaluation. Results: Local regional recurrence, especially lymph node metastasis, was the most common failure pattern (51.7%) in non-pCR ESCC patients treated with NICT+S, occurring primarily within 18 months after surgery. PORT displayed a trend of survival benefits in the post-PSM Kaplan-Meier analysis (P = 0.059, HR = 0.369, 95% CI: 0.123–1.088). It significantly improved the 1-year DFS in patients with ypN+ (92.4% vs. 73.3%), ypN2-3 (88.9% vs. 50.0%), non-T downstaging (95.7% vs. 74.6%), non-TNM downstaging (93.5% vs. 78.3%), non-smokers (94.1% vs. 72.6%), non-drinkers (100% vs. 77.4%), KPS≥90 (100% vs. 80.4%), and lower esophageal tumors (100% vs. 76.7%) (all P < 0.05).The patients without N downstaging or with moderate to well-differentiated tumors achieved superior 1-year and 2-year DFS rates when adding PORT (P < 0.05). 79 (97.3%) patients had PORT-related adverse events (AEs), and the most common AEs were Grade I-II bone marrow suppression and esophageal mucositis. Conclusions: Local regional recurrence is the most common recurrence pattern in ESCC patients undergoing NICT+S. PORT shows the significant survival benefits in patients with ypN+ or without downstaging, which exerts the potential values in improving the prognosis for LA-ESCC patients.