Age-stratified toxicity patterns of CDK4/6 inhibitors in older women with breast cancer: Disproportionality analysis from the FAERS database

BACKGROUND: Despite their benefits, the safety of cyclin-dependent kinases 4 and 6 (CDK4/6) inhibitors in older patients remains underexplored. We aimed to investigate the toxicities associated with CDK4/6 inhibitors in subgroups of older patients, through analysis of the FAERS database. METHODS: In this retrospective pharmacovigilance analysis, we identified 49,223 females with breast cancer (aged 18-100 years), in which a CDK4/6 inhibitor (palbociclib, ribociclib, or abemaciclib) was recorded as the primary suspect drug. Patients were stratified into four age groups: <65, 65-74, 75-84, and ≥85 years. Disproportionality analysis using the reporting odds ratio method was conducted to detect positive disproportionality signals between individual adverse events and CDK4/6 inhibitors. We performed age-stratified multivariate analyses to detect age-related differences. RESULTS: Acute renal failure and interstitial lung disease associated with abemaciclib were reported more frequently in geriatric age subgroups, while gastrointestinal and hematologic adverse events showed a declining reporting frequency with advancing age. Significant age-related increases in the odds of reporting dementia, hearing and vestibular disorders, lens disorders, arthritis, thrombotic events, and central nervous system hemorrhagic complications were identified in palbociclib-treated patients. Ribociclib showed increased reporting of acute renal failure, chronic kidney disease, cardiac arrhythmias, and ischemic heart disease in geriatric age subgroups, whereas the reporting frequency of liver-related adverse events declined with advancing age. CONCLUSIONS: Older adults receiving CDK4/6 inhibitors experience higher rates of renal, pulmonary, cardiac, and neurocognitive toxicities, with abemaciclib linked to renal and pulmonary, palbociclib to neurological and thrombotic/hemorrhagic, and ribociclib to renal and cardiac adverse events.