Impact of Cognitive Behavioural Therapy for Insomnia on Endocrine Therapy Adherence

The aim of this study is to investigate the impact of cognitive behavioural therapy for insomnia on adherence to endocrine therapy medication in breast cancer survivors.

Approximately 70% of breast cancer cases are hormone-receptor positive, therefore treatable with endocrine therapy medication. When taken as prescribed, this is effective in reducing the risk of breast cancer recurrence following primary treatment. However, research indicates that nonadherence (not taking medication as prescribed, whether due to forgetfulness or deliberately missing a dose) is an issue, with side effects being a consistent predictor of nonadherence. Sleep problems are one of the most common endocrine therapy side effects. The aim of this study is to explore the influence of cognitive behavioural therapy for insomnia (CBT-I) on endocrine therapy adherence in breast cancer survivors. Participants will be randomised to 1 of 2 groups: intervention, or waitlist control. Both groups will complete measures of sleep and other endocrine therapy side effects (depression, anxiety, fatigue, musculoskeletal pain, and vasomotor symptoms) at baseline, post-intervention, and 12-week post-randomisation follow-up. Following randomisation, the intervention group will receive 4 weekly group CBT-I sessions remotely through videoconferencing, whereas waitlist control participants will receive the intervention after 12 weeks, once all measures are completed. Primary outcome will be self-reported endocrine therapy adherence, with secondary outcomes including insomnia symptoms and other endocrine therapy side effects.