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The real-world, phase 4 PADMA study showed a significant and clinically meaningful improvement in time-to-treatment failure (TTF) and progression-free survival (PFS) with palbociclib plus endocrine therapy (ET) compared with chemotherapy alone in patients with high-risk HR-positive/HER2-negative metastatic breast cancer (mBC).
Sibylle Loibl, MD, PhD, from the University of Frankfurt, in Germany, noted, although “international guidelines recommend ET combined with a CDK4/6 inhibitor as first-line therapy in HR-positive/HER2-negative mBC, many patients still received chemotherapy during the initiation of the PADMA trial due to the lack of prospective data.”
The randomized, open-label, multicenter, phase 4 PADMA trial enrolled 130 men and women with HR-positive/HER2-negative mBC, an indication for mono-chemotherapy, and a life expectancy of over 6 months. Participants had no prior treatment for metastatic disease, no asymptomatic bone-only or oligo-metastatic disease, and no uncontrolled central nervous system (CNS) metastases. This trial is the first prospective study to compare palbociclib plus ET versus chemotherapy in the first-line setting. Participants were stratified by ET resistance or sensitivity and symptomatic or asymptomatic disease.
Significantly longer TFF and PFS were observed in the palbociclib plus ET arm compared with standard chemotherapy, with a median TFF of 17.2 months versus 6.1 months (HR 0.46; 95% CI 0.31–0.69; P<0.001) and median PFS of 18.7 months versus 7.8 months (HR 0.45; 95% CI 0.29–0.70; P<0.001). The data showed a positive trend toward improvement in overall survival (OS), with a median OS of 46.1 months versus 36.8 months. Notably, the palbociclib plus ET arm showed a higher incidence of hematological toxicity than the chemotherapy arm: 98.8% versus 58.6% (P<0.001). Non-hematological AEs were similar between the two arms, and no new safety signals were observed.
Prof. Loibl concluded that “the PADMA study contributed to the data that endocrine-based therapy with a CDK4/6 inhibitor is the standard of care in the first-line treatment of patients with high-risk HR-positive/HER2-negative mBC.”
Medical writing support was provided by Kulsoom Abdul.
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