Breast cancer: palbociclib-related neutropenia mostly transient, manageable

  • The Oncologist

  • curated by Miriam Davis, PhD
  • Univadis Clinical Summaries
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Takeaway

  • Palbociclib-related neutropenia was mostly transient and manageable by dose modifications for grade ≥3 events, without appearing to compromise efficacy in a newly published hematologic safety analysis of PALOMA-2.

Why this matters

  • The phase 3 trial previously demonstrated a PFS benefit for adding palbociclib to letrozole was improved PFS in estrogen receptor (ER)-positive, human epidermal growth factor receptor 2 (HER2)-negative advanced breast cancer.
  • Palbociclib-related neutropenia is common but more benign than chemotherapy-related neutropenia.

Study design

  • Randomized trial of letrozole (2.5 mg/day continuously) with (n=444) or without (n=222) oral palbociclib (n=444) given at 125 mg daily for 3 weeks on/1 week off.
  • This descriptive hematologic safety analysis was performed at baseline, days 1 and 15 (first 2 cycles), and day 1 of subsequent cycles.
  • Funding: Pfizer Inc.

Key results

  • Neutropenia was the most frequent adverse event of any grade (95.3%) associated with palbociclib+letrozole, compared with 18.9% with placebo+letrozole.
    • Grade 3 neutropenia occurred in 55.6% of palbociclib+letrozole patients.
    • Grade 4 neutropenia occurred in 11.5% of them.
  • Median duration of each grade ≥3 neutropenia episode was 7 (range, 1-115) days.
  • Neutropenia was managed by dose reductions in 24.3% of palbociclib+letrozole patients.
  • No difference in PFS with palbociclib dose-reductions vs no dose-reductions.

Limitations

  • PFS assessed only up to 9 months.