Nab-Paclitaxel Outduels Paclitaxel in HR+/HER2- and Triple-Negative MBC

Fadi Braiteh, MD

Among patients with HR+/HER2- or triple-negative metastatic breast cancer, nab-paclitaxel (Abraxane) improved time to treatment discontinuation (TTD), time to next treatment (TTNT), and had a favorable safety profile compared with paclitaxel, according to a real-world database analysis presented at the 33rd Annual Miami Breast Cancer Conference®.

Nab-paclitaxel is approved by the FDA for use in patients with metastatic breast cancer (MBC) following the failure of combination chemotherapy for metastatic disease or relapse within 6 months of adjuvant chemotherapy. The approval was based on a pivotal phase III trial that showed an overall response rate of 33% with nab-paclitaxel versus 19% with paclitaxel (P = .001) in the frontline or later settings. The median time to progression was 5.3 months versus 3.9 months, respectively (P = .006).

Despite this approval, there is a paucity of comparative effectiveness data in the real-world setting for subsets of patients with MBC who are HR+/HER2- or triple-negative. For this reason, Fadi Braiteh, MD, University of Nevada School of Medicine, and colleagues conducted a retrospective analysis comparing use of nab-paclitaxel versus paclitaxel in these breast cancer subtypes.

Braiteh et al examined data from an electronic medical record platform (Navigating Cancer). Their analysis included patients with HR+/HER2- (n = 446) or triple-negative MBC (n = 228) who received first- or second-line treatment with nab-paclitaxel or paclitaxel between December 1, 2010, and October 1, 2014.

The analysis included only patients treated in a real-world setting, not in clinical trials. Monotherapy was preferred, but patients were still included if they received combination regimens with a targeted agent. Patients received at least 2 doses of nab-paclitaxel or paclitaxel. Individuals were excluded if they received nab-paclitaxel and/or paclitaxel sequentially as first- and second-line therapy.

Nab-paclitaxel was administered at the FDA-approved dose of 260 mg/m² every 3 weeks, or 100 mg/m² or 150 mg/m² once per week for 3 of 4 weeks. Patients received paclitaxel at 175 mg/m² every 3 weeks or 80 mg/m2 weekly.

In the HR+/HER2- group, 172 patients received nab-paclitaxel, 58% in the first-line and 42% in the second line. Among the 274-patient paclitaxel cohort, 49% received the drug in the first line and 51% received it in the second line. Eighty-one percent and 95% of the nab-paclitaxel and paclitaxel groups, respectively, received the treatment weekly.

Incidence of lung, liver, and brain metastases were even between the arms; however, bone metastases was higher in the nab-paclitaxel arm at 89% versus 61%. Targeted therapy use was even at 6% in both arms, as was prior chemotherapy within 1 year, at 11% versus 8% in the nab-paclitaxel versus paclitaxel arms, respectively.

In the triple-negative breast cancer (TNBC) group, 95 patients received nab-paclitaxel, 81% in the first-line and 19% in the second line. Among the 133-patient paclitaxel cohort, 47% received the drug in the first line and 53% received it in the second line. Eighty-six percent and 96% of the nab-paclitaxel and paclitaxel groups, respectively, received the treatment weekly.

Incidence of lung, liver, and brain metastases were even between the arms; however, bone metastasis was higher in the nab-paclitaxel arm at 65% versus 37%. Targeted therapy use was comparable at 10% versus 7%, as was prior chemotherapy within 1 year, at 23% versus 17%.

In the HR+/HER2- TTD was significantly longer with nab-paclitaxel at 4.5 months versus 2.9 months with paclitaxel (P <.001). The median TTNT was significantly improved with nab-paclitaxel at 6.9 versus 5.3 months, respectively (P <.001).

The TTD was also significantly longer with nab-paclitaxel in the TNBC cohort at 3.3 versus 2.8 months with paclitaxel (unadjusted P = .005). The median TTNT with nab-paclitaxel was numerically higher; however, the difference was not statistically significant: 6.2 versus 5.4 months (unadjusted P = .580).

Across both the HR+/HER2- and TNBC cohorts, neuropathy rates were lower and antiemetics and treatments for allergic reactions to doses were used less frequently among patients receiving nab-paclitaxel. Treatment for bone loss, G-CSF, and hydrating agents were used less frequently with paclitaxel versus nab-paclitaxel.

In the HR+/HER2- arm, notable all-grade adverse events (AEs) with nab-paclitaxel versus paclitaxel included anemia (26% vs 33%), neutropenia (19% vs 14%), nausea and vomiting (12% vs 10%), pain (1% vs 11%), neuropathy (3% vs 8%), and dehydration (9% vs 7%).

The all-grade AE rates were comparable for nab-paclitaxel versus paclitaxel in the TNBC arm: anemia (24% vs 35%), neutropenia (18% vs 12%), nausea and vomiting (12% vs 5%), pain (5% vs 7%), neuropathy (1% vs 11%), and dehydration (15% vs 5%).

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