Second primary cancer after diagnosis of stomach cancer in Osaka, Japan.

The risk of developing a second primary cancer following stomach cancer was estimated from data accumulated in the Osaka Cancer Registry. Of the 38,777 male patients and 22,391 female patients newly diagnosed in the period 1966-1986 who were followed up until the end of 1986, 778 and 267 developed a second cancer other than stomach cancer, respectively, whereas the expected numbers had been 928.8 (RR = 0.84, 95% CI = 0.78-0.90) and 297.7 (RR = 0.90, 95% CI = 0.79-1.01). The risks were higher among younger patients (aged 30-54 at the diagnosis of stomach cancer) than among older patients (aged 55-69 at the diagnosis of stomach cancer). Significantly elevated risks were observed for cancers of the oral cavity & pharynx (RR = 1.56), colon (RR = 1.61) and rectum (RR = 1.56) for males, and oral cavity & pharynx (RR = 2.59) for females as second cancers. Results were substantially similar among the localized stomach cancer patients. Among younger male patients with gastrectomy, the risk of developing pancreatic cancer was elevated 10 or more years after stomach cancer diagnosis. The present study suggests the necessity of following up stomach cancer patients in order to enable the early diagnosis of digestive tract cancer.