Palbociclib in Patients With HR+/HER2- Advanced or Metastatic Breast Cancer and Bone-Only Metastasis: A Systematic...

Bone-only metastatic breast cancer remains generally incurable and is associated with considerable morbidity and mortality. The limited data available on palbociclib treatment outcomes in patients with HR+/HER2- advanced/metastatic breast cancer (ABC) and bone-only metastasis are dispersed across a myriad of publications reporting subgroup analyses from individual randomized clinical trials (RCTs) or real-world evidence (RWE) studies. Therefore, we conducted a systematic literature review of all available evidence from RCTs and RWE studies to date to better understand palbociclib treatment outcomes and inform clinical management of this patient subset.

PubMed, Embase, Cochrane Library, and relevant conference proceedings were systematically searched through December 2024. Phase 2/3 RCTs and RWE studies evaluating efficacy/effectiveness, safety, or health-related quality of life (HRQoL) of palbociclib in patients with HR+/HER2- ABC and bone-only metastasis were included.

Qualitative synthesis was performed for 61 articles, including 13 and 48 reporting RCT and RWE data, respectively. Our analysis included data from >5000 patients with bone-only metastasis treated with palbociclib. All RCTs and RWE studies (3 each) comparing palbociclib plus endocrine therapy (ET) versus ET alone in patients with bone-only metastasis showed reduced risk of disease progression and/or death with palbociclib plus ET (RCTs, 37% to 71% reduction; RWE, 26% to 45% reduction). Trends suggesting an overall survival benefit with palbociclib plus ET versus ET alone were observed in 2 RCTs (23 to 64% reduction in risk of death) and 3 RWE studies (16 to 28% reduction); however, statistical significance was not often reached. Although data are limited, available evidence suggests palbociclib is generally tolerable and maintains HRQoL in this patient subgroup.

Data from RCTs and RWE studies indicate that palbociclib plus ET is effective in patients with HR+/HER2- ABC and bone-only metastasis. Further research is needed on safety and HRQoL in this subgroup.