The Pattern of Residual Tumor After Neoadjuvant Chemotherapy for Locally Advanced Esophageal Cancer and Its Clinical Significance

Objectives: To investigate the residual pattern of esophageal cancer in the esophageal wall after neoadjuvant chemotherapy (NAC) and its clinical significance. Background: NAC is a standard treatment for locally advanced esophageal cancer; however, residual tumor patterns in resected specimens after NAC and their clinico-pathological characteristics remain unknown. Methods: One hundred twenty consecutive patients with cT3 or deeper esophageal cancer underwent curative esophagectomy after NAC and achieved grade 2 histological responses between 2000 and 2016. Hematoxylin-eosin staining of residual tumor sections revealed 4 remnant categories: Type 1: shallow, Type 2: central, Type 3: deep, and Type 4: diffuse. We examined associations between these Types and clinico-pathological factors, including prognosis. Results: Forty-five (38%) specimens had no residual tumor cells in the mucosal layer. The adventitia layer displayed the lowest residual tumor cell frequency (18%) among all layers. Types 1, 2, 3, and 4 residual tumor patterns were found in 49 (41%), 33 (28%), 9 (8%), and 29 (24%) patients, respectively. Type 4 showed the maximum standard uptake value after NAC; Types 3 and 4 had higher ratios of venous invasion than Type 1 or 2. Patients with Type 3 or 4 more frequently developed pleural dissemination or distant metastasis than patients with Type 1 or 2. Survival was similar among the 4 Types. Conclusions: After NAC for locally advanced esophageal cancer, the shallow residual tumor pattern was most common, but approximately 40% of specimens showed no tumor cells in the mucosal layer. Deep and diffuse remnant patterns were associated with high risks of pleural dissemination and distant metastasis.