Patients
The CA012 trial included 97 and 89 patients who received first-line therapy in the nab-paclitaxel and paclitaxel treatment arms, respectively. The numbers of patients per treatment arm in the intent-to-treat (ITT) population of CA024 ranged from 74 to 76. Baseline characteristics within each trial for the given patient subgroups were well balanced (Table 1).
Table 1 Baseline patient characteristics
Efficacy
Overall response rate
In the CA012 trial, ORR results for each poor prognostic factor subset were similar to the results from the general ITT population (Fig. 1). The ORR was higher with nab-paclitaxel versus paclitaxel in patients with visceral dominant disease (42 vs. 23 %; P = 0.022) and short DFI (43 vs. 33 %; P = 0.417). Similarly, ORR values among patients with poor prognostic factors in trial CA024 also corresponded to the trends in the ITT population. In both subsets, patients who received nab-paclitaxel on a qw 3/4 schedule exhibited higher ORRs compared with patients who received docetaxel (Fig. 1). Although comparisons within the short DFI subgroups failed to reach statistical significance, comparisons among patients with visceral dominant lesions did demonstrate significant differences for ORR.
The mean maximum percent tumor shrinkage was also calculated for all patients in this analysis. Waterfall plots of tumor shrinkage for study CA012 are shown in Fig. 2 as a patient-by-patient overlay of treatment groups from the least tumor shrinkage to the most tumor shrinkage. Among patients with visceral dominant metastases (Fig. 2A), the mean maximum percent tumor shrinkage was 37.4 % in the nab-paclitaxel arm versus 19.9 % in the paclitaxel arm (P = 0.006). The difference in mean percent tumor shrinkage among patients with a short DFI was not statistically significant (Fig. 2B; 39.9 % for nab-paclitaxel vs. 25.4 % for paclitaxel; P = 0.096). The tumor shrinkage data for study CA024 are shown in Supplemental Figs. 1 (visceral dominant metastases) and 2 (short DFI). For patients with visceral dominant metastases, patients who received nab-paclitaxel 300 mg/m2 q3w, 100 mg/m2 qw 3/4, and 150 mg/m2 qw 3/4 had mean maximum percent tumor shrinkages of 35.5 %, 47.5 %, and 57.1 %, respectively, versus 37.0 % for the docetaxel group. For patients with a short DFI, patients who received nab-paclitaxel 300 mg/m2 q3w, 100 mg/m2 qw 3/4, and 150 mg/m2 qw 3/4 had mean maximum percent tumor shrinkages of 36.2 %, 48.1 %, and 56.1 %, respectively, versus 32.6 % for the docetaxel group. None of the differences for study CA024 were statistically significant.
Progression-free survival
In trial CA012, PFS values in both poor prognostic factor subsets favored the nab-paclitaxel arm, although the differences were not statistically significant (Table 2). Trial CA024 also showed PFS trends among the patient subsets that reflected those of the ITT population. Comparisons of PFS in patients with visceral dominant metastases revealed statistically significant differences between nab-paclitaxel 150 mg/m2 qw 3/4 and docetaxel and between both qw 3/4 nab-paclitaxel treatment groups. In both prognostic factor subsets, the nab-paclitaxel 150 mg/m2 qw 3/4 treatment arm showed the longest PFS values (13.1 and 14.1 months in the visceral dominant metastases and short DFI groups, respectively).
Table 2 Investigator-assessed PFS
Overall survival
In this subset analysis, no comparisons for median OS reached statistical significance. In CA012, median OS was numerically higher with nab-paclitaxel versus paclitaxel in each of the subgroups (Table 3). Trial CA024 once again demonstrated similar trends in each patient subgroup compared with the ITT population. In patients with visceral dominant lesions, OS was numerically highest in patients who received nab-paclitaxel 150 mg/m2 qw 3/4, while in patients with a short DFI, the OS was numerically highest with nab-paclitaxel 100 mg/m2 qw 3/4.
Treatment exposure
As the administered dose of nab-paclitaxel in the CA012 trial was higher than that of paclitaxel, patients in that treatment arm received a higher median cumulative dose (1,560 mg/m2 for patients in both subgroups who received nab-paclitaxel vs. 962.5 mg/m2 for patients in both subgroups who received paclitaxel) and a higher dose intensity (86.6 mg/m2/week for patients with visceral dominant metastases who received nab-paclitaxel and 85.3 mg/m2/week for patients with a short DFI who received nab-paclitaxel vs. 58.3 mg/m2/week for patients in both subgroups who received paclitaxel). Treatment delays and dose reductions occurred at similar frequencies between the two treatment arms across both prognostic subgroups. Patients in the nab-paclitaxel arm received a median of 6 cycles of treatment in both groups versus 5.5 for patients in the paclitaxel arm in both groups. The average dose intensities among the two patient subgroups for the nab-paclitaxel arms in trial CA024 ranged from 99.5 to 100 mg/m2/week in the 300 mg/m2 arm, 73.7–75 mg/m2/week in the 100 mg/m2 arm, and 98.7–103.1 mg/m2/week in the 150 mg/m2 arm. The median number of cycles received was highest for the nab-paclitaxel 150 mg/m2 qw 3/4 arm among patients with visceral dominant metastases (9 vs. 8 in the other arms), but among patients with a short DFI, patients in the nab-paclitaxel 100 mg/m2 qw 3/4 arm received the highest number of cycles (8 vs. 6–7 in the other arms). Among the poor prognostic factor subgroups in trial CA024, the highest rate of dose reductions took place in the nab-paclitaxel 150 mg/m2 qw 3/4 arm (44 and 50 % among patients with visceral dominant metastases and a short DFI, respectively), followed by docetaxel (30 and 26 %, respectively), and the two other nab-paclitaxel arms, which showed similar rates of dose reductions among the patient subgroups (14–18 %).
Safety
Tables 4 and 5 show the all-grade adverse events and the grade ≥3 adverse events, respectively, for the patients with poor prognostic factors in both trials. Safety results across the patient subgroups for trial CA012 were similar to the ITT population: grade 3/4 neutropenia was more frequent for paclitaxel in the poor prognostic factor subgroups, whereas sensory neuropathy and fatigue were both more frequent for nab-paclitaxel (Table 5). In trial CA024, rates of grade 3/4 adverse events in the patient subgroups very closely matched those of the ITT populations (Table 5). Accordingly, patients in each treatment arm had similar frequencies of specific adverse events for each poor prognostic factor subgroup. In the two subgroups, the rates of grade 3/4 neutropenia and fatigue were highest for the docetaxel group and lowest in the nab-paclitaxel 100 mg/m2 qw 3/4 group (no cases of grade 3/4 fatigue were reported in either qw 3/4 nab-paclitaxel arm). The nab-paclitaxel 100 mg/m2 qw 3/4 dose also produced the lowest rate of grade ≥3 sensory neuropathy in each prognostic factor subgroup.
Table 4 All-grade toxicity
Table 5 Grade ≥3 toxicity