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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.