Outcomes associated with adjuvant radiation after lumpectomy for elderly women with T1-2N0M0 triple-negative breast cancer: SEER analysis.

Abstract

39 Background: Adjuvant Radiation (RT) may be omitted for elderly women with early stage breast cancer having favorable estrogen receptor status, however in the setting of triple negative breast cancer (TNBC), less evidence exists to guide decision making. As some findings thus far have shown TNBC to have an increased recurrence rate, this is an important subject to address. The purpose of this study is to use the Surveillance, Epidemiology, and End Result (SEER) database to evaluate how the addition of adjuvant radiation affects the survival of women ages 70 and above with T1-2, N0, M0 TNBC that undergo Lumpectomy (L). Methods: Cases diagnosed from 2010-2011 were downloaded from the SEER Database. Inclusion criteria were ages 70 and above, with T1-2N0M0 TNBC. Kaplan meier curves calculated overall survival (OS) and disease specific survival (DSS) in months (m). Log-Rank tests were performed to compare survival. Cox multivariate regression was performed to calculate Hazard Ratios (HR) and control for confounding variables including neoadjuvant chemotherapy, number of lymph nodes sampled, age, laterality, grade, T stage, extent of surgery, existence of other cancers. Results: From 2010-2011, SEER contained 109,559 cases of breast cancer with recorded results of Her-2-neu (H2N) status. Combining other receptor values, showed 12,620 triple-negative, which was 12% of cases. Of these, 6980 (55%) had stage T1-2, N0, M0. Lumpectomy was used in 4002 of these cases. There were 974 lumpectomy cases of women aged 70 and above. RT was given in 662 (68%) cases. After 23 months, L+ RT was associated with improved OS at 98.2% compared to 85.6% for L only (p=<0.001), as well as DSS at 99% for L+RT better than 94% for L only (p=0.003). Cox Regression showed radiation demonstrated improved OS (HR=0.14, p<0.001) and DSS (0.14, p=0.01). Conclusions: The use of adjuvant RT after lumpectomy for elderly women with early stage TNBC was associated with improved OS and DSS. Noting the potential for selection bias in this study, future prospective study is required to define the management of early stage triple negative breast cancer.