nab-Paclitaxel for first-line treatment of patients with metastatic breast cancer and poor prognostic factors: a retrospective analysis

Nanoparticle albumin-bound paclitaxel (nab-paclitaxel) has demonstrated clinical benefit in metastatic breast cancer (MBC) in a randomized phase III trial versus paclitaxel (CA012; N = 454) and in a randomized phase II trial versus docetaxel (CA024; N = 300). This retrospective analysis examines whether patients with poor prognostic factors demonstrate similar outcomes to the intent-to-treat (ITT) populations in these trials. This retrospective analysis evaluated the efficacy and safety of previously untreated patients with MBC with the following poor prognostic factors: visceral dominant metastases and short disease-free interval (DFI; ≤2 years). In CA012 (n = 186 first-line patients), nab-paclitaxel demonstrated a significantly higher overall response rate (ORR) versus paclitaxel in patients with visceral dominant metastases (42 vs. 23 %; P = 0.022), whereas the higher ORR for nab-paclitaxel in patients with a short DFI (43 vs. 33 %; P = NS) was not statistically significant. In CA024, a significantly higher ORR for nab-paclitaxel 150 mg/m2 versus docetaxel was observed in patients with visceral dominant metastases (76 vs. 37 %; P < 0.001). No significant differences in ORR were observed in patients with a short DFI. Although progression-free survival (PFS) and overall survival showed trends similar to ORR, statistical significance was only achieved for comparisons of PFS in patients with visceral dominant metastases in CA024 (13.1 months for nab-paclitaxel 150 mg/m2 vs. 7.8 months for docetaxel [P = 0.019] and 7.5 months for nab-paclitaxel 100 mg/m2 [P = 0.010]). Safety results were similar to previous reports of the ITT populations. nab-Paclitaxel demonstrated similar efficacy in patients with poor prognostic factors as in the ITT populations of these two trials. In each trial, ORR was significantly higher for nab-paclitaxel versus the comparator taxane among patients with visceral dominant metastases.