191 Background: Risk of second primary malignancies (SPM) is not known in gastric cancer. In this population based study, we analyzed rates of SPM in gastric cancer. Methods: We selected adult (≥18 years) patients with gastric cancer as first primary malignancy diagnosed from January 1992 to December 2011 from Surveillance, Epidemiology and End Result 13 database. We used SEER*stat’s multiple primary standardized incidence ratio (MP-SIR) session to calculate the risk of SPM diagnosed 6 months after the diagnosis of index gastric cancer. Results: Among 31,818 patients with first primary gastric cancer, 1674 (5.26%) developed 1,839 SPM with observed/expected (O/E) ratio of 1.09 (95% CI = 1.05-1.15, p<0.0001) and excess risk of 16.15 per 10,000 population. The median time to first SPM from the time of diagnosis of stomach cancer was 49 months (range 6 months to 19.08 years). There was significantly increased risk of gastrointestinal malignancies [O/E ratio 1.65 (CI=1.53-1.79, p<0.001)], thyroid cancer [O/E ratio 1.98 (CI=1.32-2.84, p<0.01)] and myeloid leukemia [O/E ratio 1.47(CI=1-2.09, p<0.05)]. Interestingly, there was significantly decreased risk of melanoma, breast cancer and prostate cancer. Conclusions: Our study showed that patients with gastric cancer are at higher risk of gastrointestinal malignancies, thyroid cancer and myeloid leukemia. Similarly, risk of melanoma, breast cancer and prostate cancer in patients with gastric cancer is lower than general population.
Risk of second primary cancers among patients with a first primary gastric cancer: A population-based study in North Portugal
