Abstract P5-13-02: Impact of Adjuvant Trastuzumab on Local Regional Recurrence: Data from the NCCTG N9831 Study

Abstract

Abstract Background: Trastuzumab (H) improves disease-free survival (DFS) in patients (pts) with HER2 positive breast cancer (BR Ca) when used with adjuvant chemotherapy. We herein compare the rates of local regional recurrence (LRR) in pts randomized to adjuvant chemotherapy with or without adjuvant H. Methods: The phase 3 randomized trial NCCTG N9831 enrolled 3505 pts with high risk HER2 positive Br Ca to evaluate the effect of adjuvant H on DFS. Pts were randomized to either doxorubicin (A) and cyclophosphamide (C) followed by paclitaxel (T); or AC→TH→H. RT was given concurrently with H after ACT chemotherapy. Pts analyzed underwent lumpectomy (L) + radiotherapy (RT), mastectomy (M) alone, or M+RT. All pts underwent sentinel lymph node biopsy alone and/or axillary dissection. 2816 pts were eligible for competing risk analysis of LRR as a first event (competing risks were distant recurrence, contralateral Br Ca, second primary cancer, or death). Median follow-up is 5.3 years. Results: Primary breast therapy included L+RT 1062 (38%), M 711 (25%), and M+RT 1043 (37%). Axillary dissection was performed in 90% of pts but less frequently with L+RT (83%) compared to M (88%) or M+RT (98%), chi-sq P<0.001. Stage at presentation was I 41%, II 51%, and III 8% with a significant greater proportion of higher stage pts undergoing M+RT, chi-sq P<0.001. Overall the 5-year LRR rate was 4.1% (95% CI 3.5-4.9%) and similar among the treatment groups: L+RT 4.7% (95% CI 3.6-6.1%), M 3.5% (95% CI 2.4-5.1%), and M+RT 2.3% (95% CI 1.6-3.4%). Among pts with a LRR, 66% were local recurrence only, 11% were local-regional, and 23% were regional only. In the L+RT patients with a LRR, the corresponding rates were 74%, 7%, and 19%, respectively. In the M patients with a LRR, the corresponding rates were 40%, 23%, and 37%, respectively. In the M+RT patients with LRR, the rates were 79%, 4%, and 17%, respectively. H is associated with a non-statistically significant reduction in the risk of LRR for pts who receive L+RT or M+RT (Table 1). No such trend was seen in the M alone group but the number of events was low. Table 1. LRR According to Local and Adjuvant Treatment Groups Conclusion: The LRR as the first reported site of failure was low with a median 5. 3 year follow-up. Adjuvant H was associated with a trend of lower LRR in the pts treated with L + RT or M+RT. This observation suggests an additive effect of RT and H on LRR that warrants further investigation. The small number of local-regional events in this one randomized trial supports further investigation of LRR across other adjuvant trastuzumab trials. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P5-13-02.