Breast cancer multifocality-multicentricity and locoregional recurrance.

Abstract

1029 Background: The impact of multifocality (MF) and multicentricity (MC) on locoregional (LR) control for invasive breast cancer, and the optimal local treatment strategy for these tumors, is unknown. In particular, there is disagreement in the literature regarding the use of Breast Conservation Therapy (BCT). We evaluated a large single institution cohort of MF and MC breast cancers to determine if they had inferior LR control rate when compared to their unifocal counterparts. Methods: MF and MC were defined pathologically as more than one lesion in the same quadrant and more than one lesion in separate quadrants, respectively. Patients were categorized by presence or absence of MF or MC disease and by the LR treatment modality received – BCT (n=256), mastectomy alone (n=466), or mastectomy plus post-mastectomy radiation therapy (n=184). 10 patients who underwent BCT for MC disease against physician advice were excluded. MF and MC tumors were analyzed both as a group and as separate entities. Kaplan-Meier product limit method was used to calculate 5-year LR control rate. Cox proportional hazards models were fit to determine independent associations of MF/MC disease with LR control. Results: Median follow up was 52 months. Out of 3722 patients with stage I-III disease who did not receive neoadjuvant chemotherapy, 906 (24%) had MF (n=673) or MC (n=233) disease. 5-year rate of LR control rate was 99% in the MF group, 96% in the MC group, and 98% in the unifocal group, (P = 0.44). Subset analysis revealed no statistical difference in LR control regardless of the type of LR treatment, (P = 0.67 in the BCT group, P = 0.37 in the mastectomy alone group, and P = 0.29 in the mastectomy plus post-mastectomy radiation therapy group). There were 21 in-breast recurrences after BCT (8.2%). After controlling for other risk factors, MF and MC did not have an independent impact on LR control rate. Conclusions: MF and MC disease are not independent risk factors for LR recurrence. Patients with MF and MC breast cancer had similar rates of LR control to their unifocal counterparts, regardless of LR treatment modality. Our 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 post-mastectomy radiation therapy.