Presentation (CTI)

OBJECTIVES: The standard treatment for hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2-) advanced breast cancer (aBC) in women combines cyclin-dependent kinase 4/6 inhibitors (CDK 4/6i) with endocrine therapy (ET). However, real-world evidence on the impact of CDK 4/6i on health-related quality of life (HRQoL) is limited. This study compares HRQoL between ET monotherapy and ET +CDK 4/6i in older women with aBC.
METHODS: This retrospective cohort study used 2007-2020 SEER-MHOS data to analyze women aged ≥65 with HR+/HER2- aBC who received ET alone or ET + CDK 4/6i and were surveyed within two years of treatment initiation. The primary predictor was CDK 4/6i use, and outcomes included HRQoL, measured by physical and mental component summary (PCS, MCS) scores and eight subscales from the Veterans RAND-12 Survey. Multivariate linear regression assessed HRQoL differences, adjusting for socio-demographic, clinical, and survey-related factors.
RESULTS: We identified 335 women (ET monotherapy = 287; ET + CDK 4/6i = 45) with a mean survey age of 74 years (SD = 6.42). No significant differences were observed in PCS [β = -3.18, p = 0.0622] or MCS scores [β = -0.97, p = 0.0604] between the two groups. Across six subscales, including physical functioning, pain, emotional well-being, emotional role limitation, social functioning, and energy/fatigue, no significant differences were observed. However, the ET + CDK4/6i group had significantly lower scores in physical role limitation [β = -3.34, p = 0.0451] and general health [β = -5.20, p = 0.0084] compared to the ET monotherapy group.
CONCLUSIONS: This population-level, real-world study is the first to compare HRQoL between ET monotherapy and ET + CDK4/6i in older women with aBC. The results indicate no significant overall differences, suggesting that adding CDK4/6i to ET does not meaningfully impact HRQoL and supports its use without major HRQoL concerns.