Survival Trends and Profiling of Gastric Mixed Adenoneuroendocrine Carcinoma (gMANEC) in the Current Era

Gastric mixed adenoneuroendocrine carcinoma (gMANEC) is a histopathologic diagnosis with at least 30% each of exocrine and endocrine components. Although prognosis is thought to be driven by the relative exocrine or endocrine dominance, gMANEC has been clinically treated as gastric adenocarcinoma (gAC). The overall survival of gMANEC as compared to gastric neuroendocrine carcinoma (gNEC) or gAC remains undefined. Using the National Cancer Database, patients with gastric tumors were queried from 2004 to 2016 for gMANEC, gNEC, and gAC histologies. Demographic and clinicopathologic features were recorded. Univariate and multivariate Cox proportional hazards analyses were performed to delineate factors associated with overall survival (OS). Overall, 404 patients diagnosed with gMANEC were identified. Patients had a median age 68 years, were majority male, and predominantly Caucasian. Gastric MANEC was more frequently poorly differentiated (73%vs 52% (gAC) vs 20% (gNEC), P < .001) with lymphovascular invasion (57%vs 38%vs 27%, P < .001) and lymph node involvement (59%vs 49%vs 36%, P < .001); these factors were associated with worse OS on univariable analysis. Finally, tumors >5 cm and lymph node involvement were independent predictors of worse survival. The median OS of patients with gMANEC was 41.5 months. Gastric MANEC and gAC have a similarly dismal prognosis and thus should be continued to treat like gAC. Pathologic nodal metastasis, tumor size and grade are useful prognostic factors.