Updated results of the combined analysis of NCCTG N9831 and NSABP B-31 adjuvant chemotherapy with/without trastuzumab in patients with HER2-positive breast cancer

Abstract

512 Background: The joint efficacy analysis of NCCTG N9831 and NSABP B-31 demonstrated improved outcomes with the addition of trastuzumab (H) to doxorubicin and cyclophosphamide (AC) followed by paclitaxel (T) in women with surgically removed HER2- positive breast cancer (NEJM 2005). Following this report, patients randomized to AC→T and less than 6 months from completion of chemotherapy were eligible to receive H. We have updated the initial combined results of these two trials. Methods: Primary and secondary efficacy endpoint were disease free survival (DFS) and overall survival (OS). Cox modeling was performed. Hazard ratios are adjusted for nodal status, tumor size, T schedule, hormone receptor status, and trial (also age for OS). Results: Among the 3,969 women enrolled (ages: 22 to 80yrs), there have been 619 events (H group: 222, non-H: 397). First events were: recurrence (511), contralateral breast disease (18), other second primary cancers (48), and death without recurrence or second primary cancers (42). The median follow-up among the 3,711 women still alive is 2.9 years (range up to 6,4 years). The 4 yr DFS rate and 4 yr OS rate respectively were: 85.9% (95%CI: 84.0–87.8%) and 92.6% (95%CI: 91.2–94.2%) in H group and 73.1% (95%CI: 70.6–75.8%) and 89.4% (95%CI: 87.6–91.2%) in non- H group. Hazard ratio for adjuvant (H/non-H) was 0.49 (P<0.0001; 95%CI: 0.41–0.58) for DFS and 0.63 (P=0.0004; 95%CI: 0.49–0.81) for OS.The rates of a first event per 1,000 women/year during yrs 1–4 were: 26.7, 52.9, 49.6 and 23.2 for H and 42.3, 102.3, 107.6 and 61.5 for non-H. The impact of crossover on clinical outcome will be explored. Conclusions: With an increase in the median follow-up of 11 months and with 225 additional events, the demonstration of substantial improvement in outcomes with the addition of trastuzumab to chemotherapy persist. This improvement continues in spite of some degree of cross-over occurring after the initial results were reported.Updated data regarding crossover outcomes and H duration (as they relate to disease free survival) will be presented. [Table: see text]