Abstract
14575 Background: In metastatic BC, Av significantly improves patient (pt) outcomes when added to paclitaxel and has been evaluated in a large, phase III trial in combination with T (AVADO). Adding X to T significantly improves overall survival and the XTAv triplet combination is highly active first-line for metastatic BC. To evaluate XTAv in early BC, we initiated a pilot, phase II study in pts scheduled to receive neoadjuvant chemotherapy. Methods: Pts with invasive HER2-negative T2–4c >2 cm, N0–3, M0 BC and no prior systemic therapy received 21-day cycles of Av 15 mg/kg (30–90-minute IV infusion, d1×5 cycles) plus T 75 mg/m2 (d1×6 cycles) plus X (950 mg/m2 bid 14d on/7d off×6 cycles). Pts underwent surgery 2–4 weeks after completing XTAv, followed by radiotherapy, chemotherapy, and hormone therapy according to institution guidelines. Pathologic complete response (pCR), the primary endpoint, was defined as no evidence of invasive tumor in the final surgical sample (T0 or DCIS). Secondary endpoints included clinical response rate (RR), breast-conserving surgery (BCS) rate, and safety. Results: Baseline characteristics (n=18) were: median age 48 years (range 34–69); T4a (6%), T3 (39%), T2 (56%); ER+ (67%); PR+ (61%). Most pts (72%) received all 6 cycles. BCS was possible in 14 pts (78%; 95% CI: 52–94); 2 additional pts (11%) had BCS followed later by mastectomy and 2 pts (11%) underwent modified radical mastectomy. Sentinel lymph nodes were negative in 10 (67%) of 15 pts undergoing sentinel biopsy. pCR rate was 22% (95% CI: 6–48). Clinical RR was 83%. T stage was T3 (17%), T2 (11%), T1 (50%), CIS (6%), T0 (17%). XTAv was well tolerated, with no unexpected toxicities. Conclusions: The 22% pCR rate suggests that the activity of XT in HER2-negative BC can be increased by adding Av. Further evaluation of this regimen in early BC is recommended. No significant financial relationships to disclose.
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