Abstract P1-12-07: A Retrospective Analysis of nab-Paclitaxel as First-Line Therapy for Metastatic Breast Cancer Patients With Poor Prognostic Factors
Authors: O'Shaughnessy J , Gradishar W , Bhar P , Iglesias J 
Published: August 2014

Background: Solvent-based taxanes have demonstrated activity in metastatic breast cancer (MBC) patients with poor prognostic factors, an important subset of patients with aggressive disease who require special consideration in treatment optimization. nab-Paclitaxel has been compared with solvent-based (sb-) paclitaxel in a randomized phase III trial (CA012; N = 454) and docetaxel in a randomized phase II trial (CA024; N = 300) for the treatment of MBC, revealing a favorable clinical benefit for nab-paclitaxel in both intent-to-treat (ITT) populations. This retrospective analysis examines whether the safety and efficacy of nab-paclitaxel observed in these trials are maintained in patients with poor prognostic factors.

Methods: This retrospective analysis evaluated safety and efficacy of the first-line treatment of patients with MBC with the poor prognostic factors of visceral dominant metastases (dominant metastatic lesion localized to visceral tissue [ie, not in bone or soft tissues]) and early disease recurrence (≤ 2 years after completing neoadjuvant or adjuvant treatment) in the CA012 and CA024 trials.

Results: In CA012 (n = 186 first-line patients), nab-paclitaxel 260 mg/m2 every 3 weeks (q3w) demonstrated a higher overall response rate (ORR) vs sb-paclitaxel 175 mg/m2 q3w in patients with visceral dominant metastases (42% vs 23%, P = .022) and in patients with early disease recurrence (43% vs 33%, P = not significant [NS]). In CA024 (n = 300 first-line patients), significantly higher ORRs for nab-paclitaxel at 100 mg/m2 (63%, P = .002) and 150 mg/m2 (76%, P &lt; .001) the first 3 of 4 weeks (qw 3/4) vs docetaxel 100 mg/m2 q3w (37%) were observed in patients with visceral dominant metastases. The difference in ORR in this subgroup between nab-paclitaxel 300 mg/m2 q3w (44%, P = NS) and docetaxel 100 mg/m2 q3w was not statistically different. As in CA012, the differences in ORR among patients with early disease recurrence in CA024 were not statistically significant (35% to 64% for the nab-paclitaxel arms vs 21% for the docetaxel 100 mg/m2 q3w arm, all P = NS). Progression-free survival (PFS) and overall survival (OS) showed trends similar to that of ORR in both trials. Statistical significance was only achieved for median PFS in CA024 among patients with visceral dominant metastases (13.1 months for nab-paclitaxel 150 mg/m2 qw 3/4 vs 7.5 months for nab-paclitaxel 100 mg/m2 qw 3/4 [P = .010] and vs 7.8 months for docetaxel 100 mg/m2 q3w [P = .019]). Safety results were similar to those of previous reports for the ITT populations; in CA024, the lowest rates of neutropenia, sensory neuropathy, and fatigue were observed with nab-paclitaxel 100 mg/m2 qw 3/4 in both patient subgroups.

Conclusions: nab-Paclitaxel showed similar efficacy in patients with poor prognostic factors to that in the ITT populations of these 2 trials. In each trial, consistent trends in favor of nab-paclitaxel were observed for ORR, PFS, and OS vs a solvent-based taxane in the specified poor prognostic factor subgroups. No new safety signals were observed.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P1-12-07.