The impact of multifocal (MF) or multicentric (MC) breast cancer on locoregional (LR) control rates is unknown. Methods. MF was defined as two or more separate invasive tumors in the same quadrant of the breast. MC was defined as two or more separate invasive tumors occupying more than one quadrant of the same breast. Patients were categorized by LR treatment: breast conservation therapy (BCT; n = 256), mastectomy (n = 466), or mastectomy plus postmastectomy radiation therapy (PMRT; n = 184). All patients with MC disease had mastectomy (10 patients treated with BCT for MC disease were excluded). The Kaplan-Meier product limit method was used to calculate 5-year LR control rate. Cox proportional hazards models were used to determine independent associations of multifocality or multicentricity with LR control. Results. A total of 906 patients had either MF disease (n = 673) or MC disease (n = 233). With median follow-up of 52 months, the 5-year LR control rate was 99% for MF, 96% for MC, and 98% for unifocal tumors (p = .44). Subset analysis revealed no difference in LR control regardless of the LR treatment (p = .67 for BCT, p = .37 for mastectomy, p = .29 for mastectomy plus PMRT). There were five in-breast recurrences after BCT in the MF group. MF and MC did not have an independent impact on LR control rate on multivariate analysis. Conclusion. MF and MC disease are not independent risk factors for LR recurrence. Patients with MF and MC breast cancer had rates of LR control similar to those of their unifocal counterparts. These data suggest that BCT is a safe option for patients with MF tumors and that MF or MC disease alone is not an indication for PMRT.
Keywords: Breast cancer; Locoregional; Multicentric; Multifocal; Outcomes.