Background: Our purpose was to examine the incidence and impact on survival of other primary malignancies (OPM) outside of the breast in breast cancer patients and to identify risk factors associated with OPM. Methods: Patients with stage 0-III breast cancer treated with breast conserving therapy at our center from 1979 to 2007 were included. Risk factors were compared between patients with/without OPM. Logistic regression was used to identify factors that were associated with OPM. Standardized incidence ratios (SIRs) were calculated. Results: Among 4,198 patients in this study, 276 (6.6 %) developed an OPM after breast cancer treatment. Patients with OPM were older and had a higher proportion of stage 0/I disease and contralateral breast cancer compared with those without OPM. In a multivariate analysis, older patients, those with contralateral breast cancer, and those who did not receive chemotherapy or hormone therapy were more likely to develop OPM after breast cancer. Patients without OPM had better overall survival. The SIR for all OPM sites combined after a first primary breast cancer was 2.91 (95 % confidence interval: 2.57-3.24). Significantly elevated risks were seen for numerous cancer sites, with SIRs ranging from 1.84 for lung cancer to 5.69 for ovarian cancer. Conclusions: Our study shows that breast cancer patients have an increased risk of developing OPM over the general population. The use of systemic therapy was not associated with increased risk of OPM. In addition to screening for a contralateral breast cancer and recurrences, breast cancer survivors should undergo screening for other malignancies.
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