NSABP FB-6: Phase II trial of weekly paclitaxel (WP) and pazopanib following doxorubicin and cyclophosphamide (AC) as neoadjuvant therapy for HER2-negative locally advanced breast cancer (LABC).

Abstract

1025 Background: Pazopanib is an oral, small molecule inhibitor of VEGFR-1, -2, and-3, PDGFR-α, and -β, and c-kit tyrosine kinases. The purpose of this trial was to determine the activity and safety profile of pazopanib when added to neoadjuvant WP following AC in LABC. The primary endpoint was pathologic complete response in the breast and nodes (pCR-BN). Methods: Women with HER2-negative stage IIIA-IIIC breast cancer were treated with AC (60 mg/m2/600 mg/m2) for 4 cycles every 3 weeks followed by WP 80 mg/m2 on days 1, 8, and 15 every 28 days for 4 cycles concurrently with pazopanib 800 mg orally daily prior to surgery. Postoperatively, pazopanib was given for 6 months. The regimen would be considered active if ≥14 responses (16% pCR rate in breast and nodes) were observed in 87 evaluable patients. Patients were considered evaluable if they received at least 1 dose of pazopanib. Results: Between July 2009 and March 2011, 101 pts (median age 51 yrs, range 30-71) were enrolled; 56% had stage IIIA, 34% stage IIIB, and 10% stage IIIC disease. 74 pts (73%) had ER-and/or PR-positive tumors and 27 pts (27%) were triple negative. 8 patients did not begin pazopanib. The pCR-BN rate in evaluable patients for whom surgical information was known was 18% (16/89). The pCR-BN rate in ER positive disease was 9% (6/65) and was 42% (10/24) in TNBC. Toxicities observed with WP and pazopanib included diarrhea (gr 2/3, 10%/5%), hand-foot syndrome (gr 2/3, 11%/1%), hypertension (gr 2/3, 12%/3%), neuropathy (gr 2/3, 14%/1%), and neutropenia (gr 3/4, 25%/1%). Liver toxicity during WP and pazopanib included ALT (gr 2/3/4, 13%/7%/1%), AST (gr 2/3, 7%/7%), and total bilirubin (gr 2, 2%). Conclusions: A regimen of WP and pazopanib following AC was active as neoadjuvant therapy in women with LABC and met the pre-specified criteria of interest. The activity in TNBC was notable. The toxicity profile of WP and pazopanib was consistent with previous experience. Support: GlaxoSmithKline.