Impact of age and comorbidities on real-world outcomes in advanced breast cancer patients treated with palbociclib in first line: a nation-wide Danish retrospective study

BACKGROUND AND PURPOSE: Palbociclib, a cyclin-dependent kinase 4/6 (CDK4/6) inhibitor, combined with aromatase inhibitors (AI), can be used in first-line treatment for estrogen receptor (ER) positive, human epidermal growth factor receptor 2 (HER2) normal advanced breast cancer (ABC). This study aims to assess the impact of age and comorbidities on the progression-free survival (PFS) and overall survival (OS) of patients treated with palbociclib and AI.

MATERIALS AND METHODS: This nationwide, retrospective cohort study included 604 women with ER positive, HER2 normal ABC treated with palbociclib and an AI between 2017 and 2021. Data were obtained from the Danish Breast Cancer Group database. Survival outcomes were analyzed based on age, Charlson Comorbidity Index (CCI), number of comorbidities, and comorbidity type. PFS and OS were estimated using the Kaplan-Meier method.

RESULTS: Median PFS for all patients was 30.6 months (95% confidence interval [CI], 27.4-34.2), and median OS was 55.6 months (95% CI, 51.8-58.9). Patients aged 65-75 years had significantly longer PFS and OS (p = 0.031 and p = 0.012) than patients aged under 65 and over 75 years. Visceral metastases were associated with shorter PFS and OS (p = 0.005). Comorbidity burden, including CCI score and comorbidity type, did not significantly affect survival outcomes.

INTERPRETATION: In our data set, univariate analyses suggest age and visceral metastases to be potential factors influencing outcomes in patients with ABC treated with palbociclib plus an AI. Comorbidities, did not significantly impact survival, suggesting that palbociclib is well-tolerated in patients with varying health profiles.

CLINICALTRIALS: gov ID: NCT06307457.