Outcomes of patients with triple-negative breast cancer treated with radiation therapy.

Abstract

88 Background: This study compares outcomes between different types of loco-regional treatment modalities used in patients with triple negative breast cancers. Methods: 299 patients with triple negative breast cancer diagnosed between April 2004 and August 2011 at a single institution and who were treated with radiation therapy were included in an IRB-approved retrospective review. Electronic charts were reviewed for demographic and pathologic data as well as outcome data including locoregional and distant recurrence. The median follow up period was 3 years. 200 (70%) patients underwent lumpectomy with whole breast irradiation (WBI). 68 (22.7%) patients received mastectomy and radiation while 31(10.4%) patients were treated with lumpectomy with accelerated partial breast irradiation (APBI). Results: Forty-nine patients (16.4%) experienced recurrence (10 local; 6 contralateral; 3 regional; 36 distant). There was a significant (p<0.0001) difference in the proportion of patients that experienced a recurrence in each treatment group: 34% (n=23) in mastectomy with radiation group; 12% (n=23) in lumpectomy with WBI group; 10% (n=3) in lumpectomy with APBI group. On univariate analysis, tumor size, tumor stage, nodal stage, overall stage, total number of positive nodes, total number of nodes removed, and whether or not the patients had an axillary lymph node dissection were significantly associated with recurrence (p<0.05). When these predictor variables, including treatment type, were examined using a stepwise cox proportional hazards regression model for recurrence, the only variables that remained significant were tumor stage (p= 0.0003) and the number of positive nodes (p= 0.0008). Survival curves were significantly different (p = 0.016) between the lumpectomy with WBI group and the mastectomy with radiation group. Over all follow-up times, the probability of survival was smallest for the mastectomy with radiation group. Conclusions: The recurrence pattern for triple negative breast cancers treated with radiation therapy was primarily distant for all treatment modalities. In our patient population, tumor stage and number of positive lymph nodes predicted for recurrence while radiotherapy technique did not.