Risk of second primary cancers among patients with stomach cancer: A population-based study in South Korea.

e16054 Background: The growing number of incident cases of gastric cancer along with improved survival results in a rising population of survivors at risk of second primary cancers (SPC). Aims: In this study, we analyzed SPC risk in stomach cancer survivors to compared the incidence of SPC with that expected in the general population. Methods: We selected adult ( > 19 years) patients with gastric cancer as first primary malignancy diagnosed from January 2010 to December 2014 using claims data from the Health Insurance Review and Assessment Service (HIRA) in South Korea. We analyzed the frequency and standardized incidence ratios (SIRs) to estimate the risk of SPC in gastric cancer survivors. Results: Among 115,914 patients with first primary gastric cancer, 3,165 (2.7%) developed SPC. The mean time to first SPM from the time of diagnosis of stomach cancer was 20.2 ± 12.5 months. The most common site was colorectal, which occurred in 529 patients (16.7%), and lung in 407 patients (12.9%), thyroid in 284 patients (9.0%), prostate in 270 patients (8.5%), liver in 260 patients (8.2%), and esophagus in 185 (5.8%). Among men, the most frequent were colorectal, lung, prostate and esophageal cancer; in women, colorectal cancer, thyroid and breast cancer were the most common. The SIR for all cancers was 1.24 in all patients, 1.30 in males, and 1.14 in females. Among both sexes, significantly higher SIRs were observed for cancers of the esophagus (6.94), small intestine (5.63) and Non-Hodgkin lymphoma (3.50). Interestingly, there was decreased risk of thyroid (SIR: 0.63), breast (SIR: 0.52) and skin cancer (SIR: 0.83). The risk of secondary cancer was found to be significantly higher within one year after primary cancer diagnosis (SIR: 2.42). Conclusions: Patients with gastric cancer were found to be at increased risk of developing SPC in compared to the general population. Close surveillance of these patients within one year after diagnosis was needed for early detection.