Risk Of Locoregional Recurrence In Triple Negative Breast Cancer Patients Treated By Breast Conserving Therapy Vs. Mastectomy: A Population-Based Study

Triple negative (TN) subtype (estrogen receptor, progesterone receptor, and human epidermal growth factor 2 receptor negative) is known to have poorer clinical outcomes compared to other breast cancer molecular subtypes. This study investigates the risk of locoregional recurrence (LRR) in women with stages I to III TN breast cancers treated with breast conserving therapy (BCT), defined as lumpectomy followed by adjuvant radiation therapy (RT) compared to modified radical mastectomy (MRM). A cohort of 657 eligible patients with stages I to III TN breast cancer diagnosed and treated with curative intent between January 1999 to December 2007, were identified from a single institution cancer registry. The medical records for all patients were reviewed and clinical, pathologic and treatment characteristics were recorded. The primary outcome was 5-years (5Y) LRR free survival. Kaplan-Meier estimates for 5Y LRR rate and 5Y overall survival (OS) was obtained, comparing those treated with BCT to MRM. Univariate and multivariate analysis was performed using the Cox proportional hazards model. With a median follow-up of 70 months, (18 - 151 months), the 5Y LRR rate for the entire cohort was 17% and 5-years OS was 68%. BCT was offered to 42% (n = 274) and MRM to 58% (n = 382). Chemotherapy was given to 71% (n = 466) with the majority receiving an anthracyclin-based regimen (84%, n = 552). In stage I and II, the proportion by T and N are: T1/2-N0 65% (n = 424), T1/T2-N1 23% (n = 150). In the T1/T2-N0 subgroup 47% received BCT (n = 198) and 53% MRM (n = 226). The 5Y LRR rate for BCT was 7% and MRM 21% (p = 0.0027); and 5Y OS for BCT was 83% and MRM 67% (p = 0.0066). Within the MRM of this subgroup, 9% (n = 19) also received adjuvant RT. In the T1/T2-N1 subgroup 39% received BCT (n = 58) and 61% MRM (n = 92), with 5Y LRR rate for BCT was 9% and MRM 24% (p = 0.0807); and 5Y OS for the BCT group was 74% and MRM 56% (p = 0.1174). Within the MRM of this subgroup, 68% (n = 63) received adjuvant RT. In multivariate Cox regression analysis, surgery (MRM compared to BCT) HR: 1.52 (1.01-2.29, p = 0.047), and presence of lymph vascular invasion HR: 1.95 (1.29 - 2.94, p = 0.002) were independent prognostic factors associated with significant reduction in OS. The use of adjuvant chemotherapy HR: 0.38 (0.25 - 0.58, p < 0.001) was an independent prognostic factor associated with significant improvement in OS. This study demonstrates a lower risk of LRR in patients treated with BCT compared to MRM in the T1/T2-N0 subgroup of TN breast cancer. Further investigation is required to determine if RT would provide higher locoregional control in women treated with MRM. Differentiating TN basal-like and non-basal phenotypes should also be addressed in future studies.