A population-based analysis evaluating risk of second primary upper abdominal cancers following radiotherapy for resectable gastric cancer

Radiotherapy is widely used in the perioperative treatment of gastric cancer. But the risk of second primary upper abdominal cancers in gastric cancer patients undergoing radiotherapy is still unclear. From the Surveillance, Epidemiology, and End Results (SEER) database, 6666 patients with gastric cancer between January 1975 and December 2010 from 8 registries were included in the analysis. Fine-Gray competing risk regression was used to analyze the cumulative incidence of second primary upper abdominal cancers. The radiotherapy-associated risk for gastric cancer patients was estimated by Poisson regression. The long-term survival was analyzed using Kaplan–Meier method. Among 6666 patients, 1138 (17.1%) patients received radiotherapy and surgery, 5528 (82.9%) patients only received surgery. The cumulative incidence of second primary upper abdominal cancers was 6.38% in patients received radiotherapy and 2.56% in patients received surgery only ( P < 0.001). In multivariable competing risk regression, radiotherapy was a risk factor of occurring second primary upper abdominal cancers ( P = 0.032; HR 1.656). In multivariable Poisson regression, radiotherapy for gastric cancer was associated with second primary upper abdominal cancers ( P = 0.002; RR 1.754). There was no significant difference in five-year survival among second primary upper abdominal cancer patients received radiotherapy or not received radiotherapy ( P = 0.167; HR 1.367). However, the 5-year survival among second primary upper abdominal cancer patients received radiotherapy was significantly lower than matched only primary upper abdominal cancer patients ( P = 0.034; HR 1.399). Radiotherapy for gastric cancer was associated with the risk of second primary upper abdominal cancers. Further research for the prevention and treatment of second primary upper abdominal cancers is necessary.