FLIPPER: Postmenopausal breast cancer patients benefit from first-line palbociclib–fulvestrant
medwireNews: Adding palbociclib to fulvestrant as first-line therapy improves 1-year progression-free survival (PFS) in postmenopausal women with hormone receptor-positive, HER2-negative, endocrine-sensitive, metastatic breast cancer, shows the phase 2 FLIPPER trial.
Joan Albanell (Hospital del Mar, Barcelona, Spain) explained at the ESMO Virtual Congress 2020 that results from the previously published PALOMA-3 trial showed survival benefits with this combination in women with advanced breast cancer who had failed on prior treatment.
He added that the results from this current analysis “provide evidence for superiority of fulvestrant plus palbociclib versus fulvestrant plus placebo in the first line treatment of endocrine sensitive [hormone receptor-positive/HER2-negative metastatic breast cancer] patients.”
Among the 189 study participants, 94 were randomly assigned to receive the CDK4/6 inhibitor palbociclib 125 mg for 3 weeks on and 1 week off per 28-day cycle plus fulvestrant 500 mg on days 1 and 15 of the first cycle and then once every 28 days, while 95 women were randomly assigned to receive placebo plus fulvestrant.
The women who received palbociclib–fulvestrant had a 1-year PFS rate of 83.5%, which was significantly higher than the 71.9% rate for women who received placebo with fulvestrant, giving a hazard ratio (HR) of 0.55, which met the prespecified superiority margin of 0.60.
The median PFS of the palbociclib arm was also significantly longer than that of the placebo arm, at 31.8 versus 22.0 months, respectively, and an HR of 0.52.
When patients were stratified by the stage and site of disease, the PFS benefit of adding palbociclib to fulvestrant remained significant among patients who had de novo metastatic or visceral disease (HR=0.30 and 0.53, respectively), but not among those who had recurrent or nonvisceral disease (HR=0.89 and 0.60, respectively).
The presenter noted that patients in the palbociclib combination arm were nearly threefold more likely to achieve a complete or partial response than those in the placebo arm, with respective objective response rates of 68.3% and 42.2%. They were also twofold more likely to derive a clinical benefit lasting at least 24 weeks, at a rate of 90.4% versus 80.0%.
Albanell said that, “as expected,” the most common adverse events (AEs) associated with palbociclib were hematologic, including grade 3–4 neutropenia (68.1%), leukopenia (26.6%), and lymphopenia (14.9%).
AEs resulted in discontinuation of palbociclib with or without fulvestrant in 19.9% of patients in the combination arm and the discontinuation of fulvestrant in 4.2% of patients in the placebo group. But overall, Albanell described the toxicity profile of the palbociclib–fulvestrant duo as “manageable.”
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