Local-regional recurrence in women with small node-negative, HER2-positive breast cancer: results from a prospective multi-institutional study (the APT trial)

PurposeWomen with HER2-positive breast cancer treated prior to effective anti-HER2 therapy have higher rates of local-regional recurrence (LRR) than those with HER2-negative disease. Effective systemic therapy, however, has been shown to decrease LRR. This study examines LRR in women with HER2-positive breast cancer treated on a single-arm prospective multicenter trial of adjuvant trastuzumab (H) and paclitaxel (T).MethodsPatients with HER2-positive tumors3.0cm with negative axillary nodes or micrometastatic disease were eligible. Systemic therapy included weekly T and H for 12weeks followed by continuation of H to complete 1 year. Radiation therapy (RT) was required following breast-conserving surgery (BCS), but dose and fields were not specified. Disease-free survival (DFS) and LRR-free survival were calculated using the Kaplan-Meier method.ResultsOf the 410 patients enrolled from September 2007 to September 2010, 406 initiated protocol therapy and formed the basis of this analysis. A total of 272 (67%) had hormone receptor-positive tumors. Of 162 patients undergoing mastectomy, local therapy records were unavailable for two. None of the 160 for whom records were available received RT. Among 244 BCS patients, detailed RT records were available for 217 (89%). With a median follow-up of 6.5years, 7-year DFS was 93.3% (95% CI 90.4-96.2), and LRR-free survival was 98.6% (95% CI 97.4-99.8).ConclusionLRR in this select group of early-stage patients with HER2-positive disease receiving effective anti-HER2 therapy is extremely low. Ifconfirmed in additional studies, future investigational efforts should focus on de-escalatinglocal therapy.