Does multicentric/multifocal breast cancer differ from unifocal breast cancer? An analysis of survival and contralateral breast cancer incidence.

Purpose we evaluated whether patients with multifocal/multicentric (M/M) breast cancer have different outcomes compared to unifocal (U) disease in terms of survival and the development of contralateral breast cancer (CBC) disease. Methods women diagnosed with stage I-III breast cancer were classified as having U or M/M disease. Prognostic factors were prospectively collected and obtained from the breast cancer outcome unit database. Univariate and multivariable analyses for the incidence of CBC were performed as well as Kaplan-Meier plots. Results 25,320 women met inclusion criteria. The 5-year cumulative incidence of CBC in the U versus M/M group was 2.3% (95% CI 2.1, 2.5) versus 2.4% (95% CI 1.6, 3.4) (P = 0.349). Breast cancer specific survival (BCSS) rate revealed a slightly worse outcome with M/M disease, RR = 1.174 (95% CI 1,004, 1.372). Conclusions M/M breast cancer did not increase the risk of metachronous CBC, but was associated with inferior BCSS.