- 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.
- 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.
- 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.
- PFS assessed only up to 9 months.