Palbociclib plus fulvestrant prolonged progression-free survival (PFS) compared with fulvestrant alone among pre- and postmenopausal Asian women with hormone receptor (HR)-positive, HER2-negative, metastatic breast cancer (MBC), according to results from the PALOMA-3 trial (ClinicalTrials.gov Identifier: NCT01942135) published in the Journal of Global Oncology.1

Treatment of MBC that becomes resistant to endocrine therapy is challenging. The purpose of this subgroup analysis was to determine the efficacy and safety of palbociclib plus fulvestrant among Asian women.

The international, double-blind, phase 3 PALOMA-3 trial randomly assigned 521 patients with HR-positive/HER2-negative MBC to receive fulvestrant plus palbociclib or placebo. Patients had disease progression while taking endocrine therapy, or during or within 12 months of completing adjuvant endocrine therapy. One previous chemotherapy regimen was allowed.

This preplanned subgroup analysis included 105 Asian women with a mean age of 54, 42% of whom were pre- or perimenopausal. Prior tamoxifen was used in 73% and prior aromatase inhibitors in 74%.

The clinical benefit response rate — defined as complete and partial responses and stable disease for at least 24 weeks — occurred in 70% and 66% of patients in the palbociclib arm compared with 52% and 53% in the fulvestrant alone arm among the Asian and non-Asian cohorts, respectively.

Treatment with palbociclib plus fulvestrant significantly prolonged PFS compared with placebo and fulvestrant. The median PFS in the palbociclib arm was not reached (95% CI, 9.2-not reached) compared with 5.8 months (95% CI, 3.5-9.2 months) in the fulvestrant only arm (hazard ratio, 0.485; 95% CI, 0.270-0.869; P = .0085).

PFS was also prolonged among non-Asians, though the PFS was shorter with a median PFS of 9.5 months (95% CI, 7.8-11.0 months) and 3.8 months (95% CI, 3.3-5.5 months) in the palbociclib and fulvestrant only arms, respectively (hazard ratio, 0.451; 95% CI, 0.343-0.593; P < .001).

Adverse events (AEs) that occurred more frequently in the palbociclib arm of the Asian cohort included hematologic AEs and stomatitis, rash, nasopharyngitis, and alopecia. There were no grade 4 events in the fulvestrant only arm, but grade 4 neutropenia (18%) and leukopenia (1%) occurred in the palbociclib arm.

According to the authors, “overall, palbociclib plus fulvestrant seems to be a reasonable treatment option in Asians with HR-positive/HER2-negative metastatic breast cancer that has progressed on prior endocrine therapy.”

Reference

  1. Iwata H, Im SA, Masuda N, et al. PALOMA-3: phase III trial of fulvestrant with or without palbociclib in premenopausal and postmenopausal women with hormone receptor–positive, human epidermal growth factor receptor 2–negative metastatic breast cancer that progressed on prior endocrine therapy—safety and efficacy in Asian patients. J Glob Oncol. 2017 Apr 11. doi: 10.1200/JGO.2016.008318 [Epub ahead of print]