Clinicopathologic Characteristics, Survival, and Treatments for Gastric Adenosquamous Carcinoma: A Population-Based Study

Background: Gastric adenosquamous carcinoma (GASC) is a rare entity with distinctive characteristics that are not fully understood. In the present study, we evaluated the characteristics of this rare disease. Methods: The U.S. Surveillance, Epidemiology, and End Results program database was searched to determine the clinicopathologic features, prognostic factors, and treatments for 246 patients with GASC and 42,735 patients with gastric adenocarcinoma (GAC). Results: Relative to GAC, GASC is associated with higher proportions of cardia involvement, high-grade tumours, deep tumour invasion, metastatic lymph nodes, and chemotherapy treatment. In patients who underwent potentially curative surgery (PCS), GASC was associated with a higher proportion of radiotherapy use and poorer overall survival (p < 0.001), although no significant difference (p = 0.802) was observed after propensity score matching (PSM). Multivariate analysis after PSM revealed that the independent prognostic factors for GASC were TNM stage [hazard ratio (HR): 1.512; p = 0.021] and regional nodes examined (HR: 0.588; p = 0.02). In patients with advanced disease, no significant difference in survival between GASC and GAC was observed (p = 0.212), although survival was significantly poorer for GASC after PSM (p = 0.019). Multivariate analysis after PSM revealed that the independent prognostic factors for GASC were invasion depth (HR: 1.303; p = 0.036) and chemotherapy (HR: 0.444; p < 0.001). Conclusions: Relative to GAC, GASC was associated with more aggressive features, although survival outcomes were similar after PCS. Chemotherapy remains a mainstay of treatment for patients with advanced GASC, but its role remains unclear for patients who are undergoing PCS.