Abstract S1-10: Association between the 21-gene recurrence score (RS) and benefit from adjuvant paclitaxel (Pac) in node-positive (N+), ER-positive breast cancer patients (pts): Results from NSABP B-28

Abstract

Abstract Background: The RS result predicts outcome in N- and N+, ER+ pts treated with adjuvant endocrine therapy. RS also predicts benefit from adjuvant chemotherapy (CT) and pts with a high RS result receive most of the benefit. We evaluated the association between RS and paclitaxel (Pac) benefit in N+, ER+ pts from NSABP B-28. Methods: B-28 compared 4 cycles of doxorubicin/cyclophosphamide (AC) vs. AC followed by Pac × 4 (AC→Pac). Pts ≥50 yrs and those<50 yrs with ER+ and/or PR+ tumors also received 5 yrs of tamoxifen starting with CT. From 8/95 to 5/98 3060 pts were accrued. The present study includes 1065 pts, ER+ by central tissue microarray IHC assay, tamoxifen-treated, and with a RS result from the Oncotype DX 21-gene assay by standard processes. Sub-distribution analyses were used for loco-regional recurrence (LRR) to account for competing risks, including distant recurrence (DR), second primary cancers, and death. Kaplan-Meier estimates and Cox models were used for other clinical outcomes. Results: Median follow-up time was 11.2 yrs. Of the 1065 pts, 386 (36%) had low RS (<18); 364 (34%) intermediate RS (18–30); and 315 (30%) high RS (≥31). RS was a significant predictor of LRR, DFS event, DR, and death in univariate analyses both in pts treated with AC and in those treated with AC→Pac (Table). Pts with low RS had similar outcomes at 10 yrs when treated with AC→Pac vs. AC (Table). The majority of Pac benefit was observed in pts with intermediate/high RS (Table). Interaction tests between RS and Pac benefit were not statistically significant (LRR: p = 0.75, DFS: p = 0.65, DR: p = 0.93, death: p = 0.30). Conclusions: RS significantly predicts risk for LRR, DR, DFS event, and death in N+, ER+ pts treated with AC or AC→Pac adjuvant CT. Pts with a low RS value have similar outcomes whether treated with AC or with AC→Pac and most of Pac benefit is evident in pts with intermediate/high RS. Although there was no significant interaction between RS and Pac benefit, these results support previous findings of lack of CT benefit in pts with a low RS result. Supported by: NCI grants U10-CA-12027, -69651, -37377, -69974, U24-CA-114732, and CA-75362; Susan G. Komen for the Cure® grants; and Bristol-Myers Squibb Pharmaceutical Research Institute Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr S1-10.