Should triple-negative breast cancer (TNBC) subtype affect local-regional therapy decision making?

Abstract

The more aggressive biologic characteristics and the current lack of targeted therapy for triple-negative breast cancer (TNBC) make local-regional management decisions challenging for physicians. TNBC is associated with patients of younger age, black race and BRCA1 mutation carriers. Distinctions between BRCA1-associated and sporadic TNBC include increased lifetime risk of ipsilateral and contralateral breast cancer after breast cancer therapy (BCT) for BRCA carriers, which is not shared by sporadic TNBC. However, the presence of a BRCA mutation should not preclude a breast-conservation approach in patients who are otherwise appropriate candidates for BCT. Data suggest that local-regional relapse (LRR) at baseline after BCT appears to be comparable for TNBC and the HER2-positive subgroups, but is about 50% greater than luminal tumors. LRR appears to be similarly increased after mastectomy; thus, TNBC should not be a contra-indication for BCT. Recent hypothesis-generating data suggest less LRR after BCT (where radiation is routinely delivered) than with mastectomy for early-stage TNBC. To date, no specific local-regional guideline recommendations for TNBC exist. Level I outcome data for TNBC using accelerated partial breast irradiation (APBI) and hypofractionated whole-breast irradiation (hWBRT) are lacking. TNBC should be treated with APBI only on clinical trials. Although hWBRT may be considered in TNBC, its association with younger age, advanced disease and use of systemic chemotherapy often precludes its use for this subtype. Until definitive treatment strategies are validated in large datasets and confirmed in randomized trials, TNBC subtype, in and of itself, should not direct local-regional management treatment decisions.