Risk of second primary cancers among patients with a first primary gastric cancer: A population-based study in North Portugal

Abstract

Background: The growing number of incident cases of gastric cancer along with improved survival result in a rising population of survivors at risk of second primary cancers (SPC). We estimated the cumulative incidence of metachronous (diagnosed >2 months after first primary cancer [FPC]) SPC in gastric FPC patients and compared the incidence of metachronous SPC with that expected in the general population. Methods: A cohort of gastric FPC patients from the North Region Cancer Registry of Portugal, diagnosed in 2000–2006 (n = 7427) was followed to 31 December 2010 for synchronous and metachronous SPCs. Cumulative incidence of metachronous SPCs taking into account death as a competing event and standardized incidence ratios (SIR) of metachronous SPCs were estimated. Results: Overall, 331 (4.5%) patients developed an SPC (26.9% synchronous and 73.1% metachronous). Over half of the SPCs occurred in digestive organs. Among men, the most frequent were colon, prostate, and trachea, bronchus and lung; in women, colon, breast and thyroid were the most common. The 10-year cumulative incidence of metachronous SPC for males was 5.7% and for females 3.5%. The SIR for all cancers was 1.30 in males and 1.20 in females. Among both sexes, significantly higher SIRs were observed for cancers of the oesophagus (males: 4.99; females: 8.03), small intestine (males: 11.04; females: 13.09) and colon (males: 2.42; females: 2.58). Conclusions: Patients with a gastric FPC were found to be at increased risk of developing SPC, mainly in digestive organs, when compared to the general population. Close surveillance of these patients may allow early detection of SPC.