Cancer risk in women with previous breast cancer.

BACKGROUND Excess risks of several second neoplasms following breast cancer have been reported. However, these risks have still to be quantified. PATIENTS AND METHODS We considered 9,729 breast cancer patients registered by the Swiss Cancer Registries of Vaud and Neuchâtel (covering about 786,000 inhabitants) and followed up from 1974 to 1998. RESULTS Overall, 443 second primary neoplasms (other than second primary breast cancers) were observed versus 389 expected [standardised incidence ratio (SIR): 1.14; 95% confidence interval (CI) 1.04-1.25]. The SIRs were above unity for endometrium (SIR = 1.5), ovary (1.3), colorectum (1.1), gallbladder (1.4), cutaneous malignant melanoma (1.4), kidney (1.4), lymphomas (1.4) and leukaemias (1.2), as well as for selected tobacco-related neoplasms. The largest excess risk was found for soft tissue sarcomas (STS) with 10 cases observed versus 3.1 expected (SIR = 3.2; 95% CI 1.5-5.9). Of these, eight occurred in potentially irradiated areas. CONCLUSIONS This analysis confirms the existence of a modest excess in several neoplasms occurring after breast cancer. The substantial excess of STS confirms the strong association between irradiation and STS.