According to a new study published in the journal The Lancet Oncology, palbociclib significantly improved progression-free survival when combined with letrozole in patients with advanced estrogen receptor (ER)-positive, human epidermal growth factor receptor 2 (HER2)-negative breast cancer.
For the phase 2 study, researchers enrolled 165 patients with advanced ER-positive, HER2-negative breast cancer and randomly assigned them to receive letrozole 2.5mg orally daily with or without palbociclib 125mg orally daily for 3 weeks of each 28-day cycle.
Results showed that median progression-free survival was 20.2 months (95% CI: 13.8 - 27.5) for the combination arm and 27.9 months (95% CI: 25.5 - 31.1) for the letrozole arm (HR = 0.488; 95% CI: 0.319 - 0.748; one-sided P = 0.0004). In regard to safety, 54% of patients assigned to the palbociclib arm experienced grade 3-4 neutropenia compared with only 1% of those in the letrozole group.
In addition, 19% of those that received palbociclib experienced grade 3-4 leukopenia and 4% experienced grade 3-4 fatigue versus 0% and 1% in the letrozole alone group, respectively. No patients experienced febrile neutropenia.
The addition of palbociclib to letrozole in this phase 2 study significantly improved progression-free survival in women with advanced oestrogen receptor-positive and HER2-negative breast cancer. A phase 3 trial is currently underway.