Study purpose: To examine whether adjuvant therapy for gastric cancer increases the risk for second primaries, and whether smoking and drinking increase the risk.
Subjects and methods: 1, 631 patients who were newly diagnosed with gastric cancer and underwent curative operation at Osaka Medical Center for Cancer and Cardiovascular Diseases during 1978-92. Incidence of second primaries were examined through linkage to Osaka Cancer Registry as of the end of December 1995. Observed number of second primaries (0) was compared with the expected according to the incidence in general population (E). Proportional hazards model was used to estimate hazard rate ratio (HR) for second primaries.
Results: 149 second primaries were observed. Seventeen cases, detected within 2 months after diagnosis of gastric cancer, were excluded. O/E ratio was 1.13 for adjuvant chemotherapy, 0.93 for immuno-chemotherapy, and 0.78 for immunotherapy, while 1.14 for operation only (not significant). Age-, sex-, and stage-adjusted HR was 1.02 (95% C.I. 0.69-1.50) for chemotherapy, 0.80 (0.41-1.57) for immuno-chemotherapy, and 0.60 (0.08-4.34) for immunotherapy, as compared with the risk for operation only. Among males, HR for current smokers vs. never smokers was 1.82 (1.02-3.26).
Conclusions: Adjuvant therapy for gastric cancer did not significantly increase the risk for second primaries, while smoking elevated it. J Epidemiol, 2000 ; 10 : 300-304