The effect of margin status and molecular subtype on women with invasive breast cancer treated with breast-conservation therapy.

Abstract

83 Background: A consensus statement was recently published by SSO/ASTRO on margins for stage I and II invasive breast cancer treated with breast conserving surgery (BCS). We examined patients with invasive breast cancer who underwent BCS to determine if margin status and molecular subtype influence outcomes. Methods: We the reviewed charts of 754 Stage I-III breast cancer patients treated with BCS from 2003-2010. Margin status was defined as negative ≥ 2mm, close < 2mm and positive as tumor on ink. Conventional receptor analyses were used as markers for molecular subtype classification (luminal A, luminal B, Her2 positive, and basal). Clinicopathologic variables were tested using the Fisher’s exact, Chi-square, ANOVA F-test, and Kruskal-Wallis tests. A Cox proportional - Hazards model was used to measure the impact of these variables on locoregional recurrence (LRR), breast cancer-specific (BCSS) and overall survival (OS). Results: The median age of the cohort was 58 (range 27-89 years). Most were white (88%), had T1 tumors (76%), luminal A tumors (66%), invasive ductal histology (80%), and were node negative (76%). Of the 754 patients, 26% had close margins, 2% positive margins, and 9% unknown margins. With a median follow-up of 5.2 years, OS was 92%. Twenty eight patients had a LRR with a median time to recurrence of 5.1 years. On multivariate analysis, molecular subtype, pathologic grade (p=0.01), and use of radiation (p<0.0001) were the only significant predictors of LRR. Unknown subtype, compared to Luminal A, was less likely to have a LRR (p=0.04). Basal (p=0.0002), Her2+ (p=0.03), Luminal B (p=0.002) and unknown subtype (p=0.04) had worse BCSS compared to Luminal A tumors. Margins had no impact on LRR or BCSS but those with close margins and unknown margins had worse OS compared to negative margins (p=0.01, p=0.007). Variables predictive of OS were margins, age, race, node status, chemotherapy, anti-endocrine therapy, and radiation. Conclusions: In this cohort treated with BCS, molecular subtype was a predictor of LRR and BCSS but not OS. Margin status did not impact LRR and BCSS. Although margin status was a predictor of OS, tumor biology remains the significant determinant of outcome.