Second primary gastric cancers in a region with an overall high risk of gastric cancer.

OBJECTIVE

To compare the incidence rates of gastric cancer among cancer survivors with those in the general population, and estimate the probability of a gastric second primary cancer being diagnosed 10 years after any other first primary cancer.

METHOD: A cohort of first primary cancers (other than gastric) diagnosed in Northern Portugal between 2000 and 2006 (n=64,648) was followed until 31/12/2012 for gastric second primary cancers. Incidence rates, standardized incidence ratios and the cumulative incidence of gastric second primary cancers were calculated.

RESULTS

Overall, 330 patients developed gastric second primary cancers (21.2% within two months). The incidence rate of gastric second primary cancers was higher within two months of the first primary cancer (standardized incidence ratios: 5.20 in males and 7.89 in females), particularly among survivors of cancers of the oesophagus, colon and rectum, than in the remaining period (standardized incidence ratios: 0.64 in males and 0.74 in females). The 10-year risk of a gastric second primary cancer was 0.6% (males: 0.7%; females: 0.4%).

CONCLUSION

The incidence rate of gastric second primary cancers among cancer survivors was higher than in the general population only soon after the first primary cancer, and lower thereafter. Despite the high mortality, the probability of a gastric second primary cancer within 10-years of the first primary cancer was 0.6%.