Second primary cancers following breast cancer in the Japanese female population

To assess the risk of developing second primary cancers following breast ca ncer in Japanese females, we performed a retrospective cohort study of 2786 patients who were newly diagnosed with breast cancer at our hospital betwe en 1970-1994, until the end of 1995 (average follow-up period, 8.6 years). The expected number of each second primary cancer was calculated by multipl ying the number of appropriate person-years at risk by the corresponding ag e- and calendar period-specific cancer incidence rates for women obtained f rom the Osaka Cancer Registry, One hundred and seventeen patients developed a second primary canter other than subsequent breast cancer, yielding an o bserved-to-expected ratio (O/E) of 1.3 [95% confidence interval (CI)=1.1-1. 6]. The risk for developing a second primary cancer was significantly eleva ted during the first year following the diagnosis of breast cancer, and dec reased with the passage of time to unity, A significantly increased risk wa s noted for the development of ovarian cancer (O/E=2.4, 95% CI CI=1.0-4.6), thyroid cancer (O/E=3.7, 95% CI=1.5-7.6) and non-Hodgkin's lymphoma (NHL) (O/E=3.5, 95% CI=1.4-7.1) among the breast cancer patients compared with th e general population. Patients who received hormonal therapy as the breast cancer treatment showed a significantly increased risk for ovarian cancer ( O/E=5.5, 95% CI=1.8-12.9). Patients who received chemotherapy as the breast cancer treatment had an increased risk, for NHL (O/E=5.0, 95% CI=1.6-11.6) . These findings indicate that Japanese female patients with breast cancer had a 30% higher risk of developing a second primary cancer than the genera l population, the higher risk being manifested in the early period followin g the diagnosis of breast canter, Medical surveillance of breast cancer pat ients for NHL, as well as for ovarian cancer and thyroid cancer, is require d.