Variation in uptake and dose reduction of CDK4/6 inhibitors for the treatment of breast cancer in England, 2019-2024: a descriptive observational study using OpenPrescribing Hospitals

Background The number of novel cancer therapies approved for use in England by the National Institute for Health and Care Excellence is increasing. Monitoring the adoption of new therapies is important to assess equity of access and evaluate real-world prescribing practices. OpenPrescribing Hospitals has recently been launched to facilitate analysis of open secondary care medicines data in England. Using this platform, we set out to describe the use of cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors, including the frequency of dose reductions, within National Health Service (NHS) hospitals in England between January 2019 and December 2024. Methods The monthly proportion of each CDK4/6 inhibitor relative to total CDK4/6 inhibitor use was calculated at hospital level. Regional variation was assessed across Cancer Alliances by comparing the proportions of each CDK4/6 inhibitor used within each alliance in 2021 and 2024. Use of lower strength palbociclib and abemaciclib was used as a proxy for dose reductions. Findings There was more than a 3-fold increase in the use of CDK4/6 inhibitors between 2019 and 2024. In 2019, 78.6%, 11.9% and 9.5% of CDK4/6 inhibitors used were palbociclib, abemaciclib and ribociclib, compared with 40.2%, 41.2% and 18.6% in 2024. There was variation in the relative percentage change in use of each agent by Cancer Alliance. Use of lower strengths was common for both palbociclib (60%) and abemaciclib (63%). Interpretation Changes in usage appeared responsive to publication of key evidence and regulatory milestones. There was a higher apparent frequency of dose reductions than reported in clinical trials. OpenPrescribing Hospitals is an accessible, publicly available tool for understanding uptake and use of medicines in NHS hospitals in England.