2ND-PRIMARY CANCERS IN BREAST-CANCER PATIENTS IN SLOVENIA

Data from the Cancer Registry of Slovenia were used in a cohort study to determine whether the incidence of second primary cancers in patien ts with first primary breast cancer differs from the incidence expecte d in the general population. Special interest was given to long-term s urvivors. The expected numbers of second primary cancers were calculat ed by multiplying the number of appropriate person-years at risk by th e corresponding age- and calendar-period-specific cancer incidence rat es for women in Slovenia. The risk of a second primary cancer was expr essed as the standardized incidence ratio (SIR). Of the 8,917 patients newly diagnosed in the period 1961-85 and followed-up to the end of 1 994, 547 (6.2 percent) developed second primary cancers, whereas 410 ( 4.7 percent) were expected (SIR = 1.3, 95 percent confidence interval [CI] = 1.2-1.4). The risk was higher among younger patients. In long-t erm survivors, the risk was increased significantly for second primary cancer of the breast (SIR = 1.4, CI = 1.1-1.7), lung cancer (SIR = 1. 6, CI = 1.1-2.3), melanoma (SIR = 2.7, CI = 1.5-4.4) and non-melanoma skin cancers (SIR = 2.0, CI = 1.6-2.4), corpus uteri cancer(SIR = 1.6, CI = 1.2-2.1), ovarian cancer(SIR = 2.3, CI = 1.7-3.0), and thyroid c ancer (SIR = 2.5, CI = 1.2-4.6). Our results confirm the findings of s everal cohort studies carried out in Europe, the United States, and Ja pan, indicating that breast cancer patients should be monitored carefu lly for the occurrence of second primary cancers.