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.