A randomized, double-blind phase II study of the oral tyrosine kinase inhibitor (TKI) axitinib (AG-013736) in combination with docetaxel (DOC) compared to DOC plus placebo (PL) in metastatic breast cancer (MBC)

Abstract

1003 Background: Single-agent DOC is commonly used to treat MBC. Axitinib (AG) is a potent TKI of VEGFRs. A phase I lead-in study identified 80 mg/m2 q3wks of DOC in combination with 5 mg BID of AG as the recommended phase 2 dose. The primary objective was to determine whether the time to progression (TTP) of AG+DOC arm is superior to DOC+PL. Methods: Pts with no prior chemotherapy for MBC and =12 mos from adjuvant chemotherapy (aCT), measurable disease, ECOG performance status (PS) of 0–2, and no uncontrolled brain metastases were randomly assigned (2:1) to receive treatment with either DOC+AG or DOC+PL without prophylactic growth factor in cycle 1. Tumor measurements were performed q9wks. Pts were stratified according to estrogen receptor (ER) status, prior aCT and PS (0–1 or 2). Results: A total of 168 pts were randomized. 92 pts had received prior aCT, 27 of whom received a prior taxane. Treatment arms were well balanced for prior adjuvant and taxane therapy. A median of 7 cycles of AG+DOC (range: 1–18) and 7 cycles of DOC+PL (range: 1–23) were administered. The most common non-hematologic adverse events observed in the AG+DOC arm included diarrhea (60%), nausea (53%), alopecia (51%), fatigue (49%), stomatitis (44%) and vomiting (40%). Grade 3/4 adverse events that were increased with AG+DOC vs DOC included febrile neutropenia (16 vs 7%), fatigue (13 vs 5%), stomatitis (13 vs 2%), diarrhea (11 vs 0%) and hypertension (5 vs 2%). Other grade 3/4 hematologic toxicities were similar in both arms. The median TTP (by RECIST) was 8.2 mo with AG+DOC arm and 7 mo with DOC+PL arm with a hazard ratio of 0.73 (prespecified, one-sided p=0.052). The overall response rate (ORR) was 40% for AG+DOC arm and 23% for DOC+PL arm (p=0.038). In a hypothesis-generating subgroup analysis, the median TTP in patients receiving prior aCT was 9.0 mo with AG+DOC arm and 6.3 mo with DOC+PL arm with a hazard ratio of 0.54 (p=0.012). Within this stratum, ORR was 45% for AG+DOC arm and 13% for DOC+PL arm (p=0.003). Conclusions: The anti-angiogenic TKI AG combined with DOC (80 mg/m2 q3wks) as first line therapy for MBC has an acceptable safety profile and promising anti-tumor activity. No significant financial relationships to disclose.