A quarter of women stop taking the breast cancer drug abemaciclib before completing the recommended two-year course, and adherence to a similar drug, ribociclib, appears even worse. This matters because nearly 57,000 women are diagnosed with primary breast cancer each year in the UK, and 75–80% have oestrogen-sensitive tumours. These women are prescribed daily endocrine therapy for five to ten years after surgery, and now CDK4/6 inhibitors like abemaciclib can further reduce recurrence risk. But trial data show 26% of patients discontinued abemaciclib early, undermining its potential benefit. The SWEET-PLUS project will identify why women stop or skip these drugs. Researchers will interview about 25 women—including those from groups with worse outcomes—and run focus groups with roughly 20 healthcare professionals. In the final phase, the team will work with breast cancer patients to co-design a support intervention, building on an existing programme that already helps women adhere to endocrine therapy. If successful, the intervention could reduce breast cancer recurrences and deaths, benefiting patients, their families, and the NHS by ensuring more women complete the full treatment course.
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Research Questions What are the determinants of (non-)adherence to CDK4/6 inhibitors in women with early-stage breast cancer? What information and support do patients and clinicians believe is needed to support adherence to CDK4/6 inhibitors, and how can this best be delivered? Background Almost 57,000 women are diagnosed with a primary breast cancer annually in the UK. Although treatments are highly effective, and most women have early-stage disease, the cancer may still recur up to 30 years later. 75-80% of women have oestrogen sensitive tumours (known as ER+ve) and are recommended to take endocrine therapy daily for 5-10 years after surgery +/ radiotherapy/chemotherapy to reduce recurrence risk. Biological therapies, specifically CDK4/6 inhibitors, may further reduce recurrence risk. Abemaciclib has recently been approved by NICE for use alongside endocrine therapy in early ER+ve disease. However, in trials, 26% of patients discontinued abemaciclib before the recommended two-year treatment period. Positive trial results are emerging for ribociclib in early disease and it is likely to be available soon. However, adherence appears even poorer for ribociclib. To achieve full benefits of these biological therapies, women need to be supported to take them as recommended. Aim SWEET-PLUS will identify determinants of (non-)adherence to CDK4/6 inhibitors in early ER+ve breast cancer, and use that information to co-develop an intervention to support women adhere to these drugs alongside endocrine therapy. Methods Phase 1 will explore experiences of CDK4/6 inhibitor utilisation among women with early ER+ve breast cancer. Semi-structured interviews will be conducted with ~25 women (with quotas for women from groups with worse outcomes), exploring understanding of the medication, experiences of use, adherence and what did/might have helped or hindered adherence. Phase 2 will involve focus groups with healthcare professionals (~20 participants across 3/4 groups) to investigate their experiences of prescribing CDK4/6 inhibitors and associated follow-up care, and how/what they advise women about adherence. In Phase 3, the research team will work in partnership with breast cancer patients to co-design an intervention to support women adhere to CDK4/6 inhibitors (alongside endocrine therapy) for the recommended period. This will be an "add-on module" to our HT&Me intervention which supports adherence to endocrine therapy in women with early stage ER+ve breast cancer (NIHR200098). Initial pre-testing and refinement will be conducted. Timelines Prior to start: ethical/HRA approvals; site R&D review Months 1-8: Phase 1 recruitment & analysis Months 4-12: Phase 2 recruitment & analysis Months 13-16: Phase 3 workshops and module co-design Months 17-18: Phase 3 intervention pre-testing PPI Women with breast cancer have been involved in developing the application and will be actively involved in delivery, including reviewing patient-facing materials, advising and supporting recruitment, reviewing results and dissemination. Anticipated Impact and Dissemination The intervention developed will support adherence to CDK4/6 inhibitors in early breast cancer. Long-term, this will reduce recurrences and breast cancer deaths, benefiting patients, families, and the NHS. Results will be published in papers, briefings, infographics, and a screencast/podcast. The team will work with charities, commissioners and other organisations to ensure findings are used to benefit patients.
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