Pattern of tumor regression after neoadjuvant chemoimmunotherapy for esophageal squamous cell carcinoma

Background: Immune checkpoint inhibitors have been increasingly applied for esophageal cancer. The aims of this study were to evaluate the pattern of tumor regression after neoadjuvant chemoimmunotherapy. Methods: From January 2020 to December 2021, 138 patients with esophageal squamous cell carcinoma who had esophagectomy after neoadjuvant chemoimmunotherapy were reviewed. Surgical and pathological results were analyzed, and tumor regression pattern was evaluated. Results: Of the 138 patients, 65 (47.1%) patients had chemotherapy combined with camrelizumab, 48 (34.8%) with pembrolizumab, 13 (9.4%) with tislelizumab, and 12 (8.7%) with sintilimab. Sixty-four patients (46.4%) underwent McKewon procedure, and 74 (53.6%) Ivor-Lewis procedure, respectively. There were 131/138 patients (94.9%) who had R0 resections, and the median number of resected lymph nodes was 28. Pneumonia was the most common complication after surgery (14.5%). Pathological complete regression occurred in 28 patients (20.3%). Regarding to residual tumor, there were 50 patients (36.2%) with residual tumor in the mucosa, 81 (58.7%) in the submucosa, 85 (61.6%) in the muscularis propria, 47 (34.1%) in the adventitia and 71 (51.4%) in the lymph nodes. There were 88 patients with no residual tumor in the mucosa, of whom 60 (68.2%) had residual tumors in other layers or in the lymph nodes. Conclusions: In this retrospective study, esophagectomy after neoadjuvant chemoimmunotherapy is safe with acceptable surgical risk. Preferential clearing of tumor cells in mucosa layer is common after immunotherapy, while the rate of complete pathological response is relatively low, indicating surgery is still necessary.