Breast cancer multifocality-multicentricity and survival outcomes.

Abstract

1104 Background: Studies have consistently shown a correlation between multifocal (MF) and multicentric (MC) breast cancers and the rate and extent of lymph node metastases, but the literature is divided on whether there is a corresponding impact on survival outcomes. In the absence of compelling evidence to dictate otherwise, the convention according to current TNM staging guidelines has been to stage and treat MF and MC cancers according to the diameter of the largest lesions, without taking other foci of disease into consideration. We evaluated a large single institution cohort of MF and MC breast cancers to determine their frequency, clinico-pathological characteristics and effect on survival outcomes. 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. Kaplan-Meier product limit method was used to calculate relapse-free survival (RFS), breast cancer-specific survival (BCSS) and overall survival (OS). Cox proportional hazards models were fit to determine independent associations of MF/MC disease with survival outcomes. Results: Out of 3924 patients, 942 (24%) had MF (n=695) or MC (n=247) disease. MF and MC disease was associated with higher T-stages (T2 26% vs. 21.6%; T3 7.4% vs. 2.3%, P<0.001), higher nuclear grade (grade 3 44% vs. 38.2%, P<0.001), lymphovascular invasion (26.2% vs. 19.3%, P<0.001) and lymph node metastases (43.1% vs. 27.3%, P<0.001). After a median follow up of 51 months, MC but not MF breast cancers were associated with significantly worse 5-year RFS (90% vs. 95%, P=0.02) and BCSS (95% vs. 97%, P=0.01), and a trend towards worse 5-year OS (92% vs. 93%, P=0.08). After controlling for other risk factors, multifocality and multicentricity did not have an independent impact on RFS, BCSS or OS. This was true for the subset of T1N0 breast cancers as well. Conclusions: MF and MC breast cancers occurred in 24% of the cases and were associated with poor prognostic factors, but they were not independent predictors of worse survival outcomes. Our findings support the current TNM staging system of using the diameter of the largest lesion to assign T-stage.