LAUSR

Although neoadjuvant chemotherapy (NAC) has recently became a standard treatment for locally-advanced esophageal squamous cell carcinoma (ESCC), residual pattern of cancer cells in resected specimen after NAC has not been clarified yet. A total of 120 patients with cT3 or T4 ESCC who underwent curative esophagectomy after NAC and achieved grade2 as histological efficacy between 2000–2016 were analyzed. We classified the pattern of residual tumor into 4 categories; Type 1: Shallow remnant (between mucosa and submucosa), Type 2: Central remnant (between submucosa and muscularis propria), Type 3: Deep remnant (between muscularis propria and adventitia), and Type 4: diffuse remnant (between mucosa/submucosa and muscularis propria/adventitia) and examined its relationship with clinicopathological factors and prognosis. The tumor remnant type was categorized as follows; Type 1/Type 2/Type 3/Type 4: = 49/33/9/29 cases. Forty-five cases had no residual cancer cells in the mucosal layer. The positivity rate of lymphatic invasion was similar between 4 categories, while the positivity of venous invasion was significantly higher in Type 3 and 4 as compared to Type 1 or 2 (P = 0.04). Regarding the pattern of recurrence, lymph node recurrence was more common in Type 1 (69%) and Type 2 (83%) compared to Type 3 (50%) or Type 4 (38%) (P = 0.29). Notably, more patients with Type 3 or 4 developed pleural dissemination or distant metastasis as compared with those with Type 1 or 2 [pleural dissemination: Type 1/2/3/4: 0%/0%/50%/38% (P = 0.029), distant metastasis: Type 1/2/3/4: 31%/13%/50%/88%, (P = 0.11)]. No significant difference in 2-year recurrence-free survival rate was identified among 4 categories (Type 1/2/3/4: 65.9%/78.0%/74.1%/71.8%, P = 0.757). The most common pattern of residual tumor after NAC for advanced ESCC was shallow remnant although approximately forty percent of cases inversely showed tumor disappearance at least in mucosal layer. Lymph node metastases was the predominant pattern of disease recurrence in patients with the shallow and middle remnant type while deep and diffuse remnant pattern were significantly associated with pleural dissemination and distant metastasis. All authors have declared no conflicts of interest.