Asian women also benefit from palbociclib plus letrozole

Results from the PALOMA-4 trial confirmed that palbociclib plus letrozole significantly prolonged progression-free survival (PFS) as compared with placebo plus letrozole in an Asian cohort in the first-line setting for ER-positive, HER2-negative advanced breast cancer.

Prof. Binghe Xu (Peking Union Medical College, Beijing, China) presented results of PALOMA-4 (NCT02297438), currently the largest randomised phase 3 study of a CDK4/6 inhibitor in Asian women with ER-positive, HER2-negative advanced breast cancer in the first-line setting [1]. The multicentre, randomised, double-blind phase 3 study PALOMA-4 was designed to compare the clinical benefit following treatment with letrozole in combination with palbociclib versus letrozole in combination with placebo in Asian postmenopausal women with ER-positive, HER2-negative advanced breast cancer who have not received prior systemic anti-cancer therapies for their advanced/metastatic disease. A previous phase 1 study showed that this combination had similar safety and pharmacokinetic characteristics in Asian women [2].

The experimental arm of palbociclib (125 mg, orally once daily on day 1–21 of every 28-day cycle followed by 7 days off treatment) in combination with letrozole (2.5 mg, orally once daily, continuously) was compared with placebo plus letrozole. The primary endpoint was PFS, with key secondary outcomes being overall survival, number of participants with objective response, duration of response, and quality of life.

The primary endpoint was met: median PFS was 21.5 months with palbociclib + letrozole versus 13.9 months with placebo + letrozole (HR 0.677; 95% CI 0.529–0.867; P=0.0012). The PFS benefit of palbociclib + letrozole versus placebo + letrozole was observed across subgroups, except in patients aged ≥65 years.

Febrile neutropenia was reported in 2.4% of patients treated in the experimental arm. Serious adverse events occurred in 15.5% of patients in the palbociclib arm and 9.4% of patients in the placebo arm. Safety was determined to be similar to patients in previous trials with this combination, and no new safety signals were detected.

Prof. Xu concluded that the PFS data from this Asian cohort was consistent with findings from the PALOMA-2 study of mostly White patients. In addition, no new safety concerns associated with palbociclib plus letrozole were identified in Asian women. This study supports the use of palbociclib plus letrozole as first-line therapy in postmenopausal Asian women with ER-positive, HER2-negative advanced breast cancer.

1. Xu B, et al. PALOMA-4: Primary results from a phase III trial of palbociclib (PAL) + letrozole (LET) vs placebo (PBO) + LET in Asian postmenopausal women with estrogen receptor–positive/human epidermal growth factor receptor 2–negative (ER+/HER2–) advanced breast cancer (ABC). Abstract 228MO, ESMO Congress 2021, 16–21 September.
2. Xu B, et al. Cancer Chemother Pharmacol. 2021;88(1):131-141.

 

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Posted on 19 November 2021