Long-term prognosis of mixed histological-type gastric cancers cured by endoscopic resection: a multicenter...

Gastric cancer is divided into differentiated and undifferentiated types and sometimes exhibits mixed histology. However, the risk of gastric cancer-related death after curative endoscopic resection for mixed histology remains unknown. This study evaluated the long-term prognosis of mixed histological type gastric cancers treated with endoscopic resection.

Data from a Japanese multicenter prospective cohort study were analyzed. Patients with single gastric cancer lesions who underwent curative endoscopic resection were included and divided into those with pure or mixed histological types. Patients with both types of gastric cancer were compared in terms of 5-year overall survival and 5-year disease-specific survival related to primary gastric cancers.

Pure histological type was observed in 6434 patients with 6434 lesions, and mixed histological type was observed in 161 patients with 161 lesions. Overall survival was not significantly different between patients with both types (p = 0.415). The 5-year disease-specific survival was lower in patients with mixed histological type than in those with pure histological type (p = 0.003). After stratification by curative endoscopic resection criteria, in cases of pT1a/M, differentiated-type dominance, tumor size ≤ 3 cm with ulcerative findings, no lymphovascular invasion, and R0 resection, the 5-year disease-specific survival was significantly lower in patients with mixed histological type than in those with pure type (p < 0.001).

The long-term prognosis in cured cases, including those with mixed histological type, was favorable. Stratification analysis showed that mixed histological types with ulcers were more likely to cause primary gastric cancer-related death than pure histological type and might need more careful surveillance.

UMIN Clinical Trial Registry, UMIN000005871.