Retrospective study of incidence, risk factors, and tumor spectrum of second primary cancers after gastric cancer

The development of second primary cancers (SPCs) has become an important late effect in gastric cancer (GC) survivors; yet its incidence, risk factors, and clinical implications are poorly defined. A multicenter retrospective study in China, with a follow-up of 16 years, evaluated long-term risk of SPCs in the Multidisciplinary Alliance of Gastric Integrative Studies (MAGIS) cohort. Among 11,027 GC survivors (8,519 men and 2,508 women), 241 (2.19%) developed SPCs. The cumulative incidence of SPCs 5, 10, and 15 years after gastrectomy was 1.25% (95% CI 1.03-1.46), 2.97% (2.55-3.39), and 4.15% (3,40-4.91), respectively. The most frequent SPCs were lung (23.2%), colorectal (21.6%), and esophgeal (12.9%) cancers, with marked sex-specific differences: lung cancer predominated in males, while cervical cancer was most common in females. Factors associated with SPC occurrence included older age at gastrectomy, chronic HBV/HCV infection, family history of cancer, and elevated preoperative systemic inflammation. The derived model stratified patients into low-, intermediate-, and high-risk groups, with corresponding 10-year SPC risks of 2.07%, 3.61%, and 4.33%. SPCs detected during asymptomatic surveillance were more frequently diagnosed at stage I than those identified after symptom onset (47.4% versus 17.6%; p<0.001). The authors conclude that SPCs represent an important long-term health burden among GC survivors.