Supporting adherence to adjuvant CDK4/6 inhibitors in women with early breast cancer (SWEET-PLUS): protocol for a...

Breast cancer is the most common cancer in women in the UK. For women who have early-stage oestrogen-receptor positive (ER+ve) disease, daily oral adjuvant endocrine therapy reduces risk of recurrence. Recently, CDK4/6 inhibitors, a form of biological therapy, have been approved for use alongside endocrine therapy. However, trial data suggest there may be challenges with adherence to CDK4/6 inhibitors. This study aims to explore the experiences of adherence and support needs of women who have been prescribed CDK4/6 inhibitors for early ER+ve breast cancer. It will also co-develop an intervention to support women with adherence to these drugs alongside endocrine therapy through an evidence-based, theory-informed and patient-centred approach.

The SWEET-PLUS study has three phases. Phase I uses semi-structured interviews or focus groups to explore the experiences of women with early breast cancer who have been prescribed CDK4/6 inhibitors. It will also explore their support needs and experiences of adherence. Phase II involves interviews or focus groups with healthcare professionals who support CDK4/6 inhibitor prescription and associated care to understand the existing support and unmet needs. Phase I and II findings will inform phase III, which comprises workshops and user testing interviews to co-develop an intervention to support women with adherence to CDK4/6 inhibitors alongside endocrine therapy. This will be delivered as an additional module prototype designed for future integration into the existing HT&Me intervention, which supports women with adherence to endocrine therapy.Data from phases I and II will be analysed using a framework approach-based thematic analysis. Phase III data will be analysed through content analysis.

SWEET-PLUS received ethical approval from the National Health Services (NHS) Health Research Authority (Cambridge East Research Ethics Committee (25/EE/0220)). Research findings will be disseminated through peer-reviewed journal articles and via international and national conferences. Further dissemination will be guided by patient and public involvement.