Table 1. Summary of intervention components in the ROSETA pilot trial.

Component	Target	Description
SMS	Forgetfulness/habit formation	SMS messages will be sent over 4 months providing practical strategies to support regular medication taking each day. The messages will be sent daily for 2 weeks, twice weekly for 8 weeks and weekly for 6 weeks.
Information Leaflet	Medication beliefs	A written information leaflet containing five elements; an explanation of how AET works with diagrams to supplement, visual displays of the benefits of AET, accurate information about the side effects of AET, answers to common concerns about AET and quotes and pictures of breast cancer survivors.
ACT	Psychological flexibility/ psychological distress	A guided self-help intervention based on ACT principles involving four skills; mindfulness, unhooking, following values and living beyond labels. The modules consist of a participant booklet, home practice tasks and audio files. The modules are supported by five individual sessions with a psychologist; 1 x 15 minute opening session, 3 x 25 minute sessions following modules 1, 2 and 3, and 1 x 15 minute closing session following module 4.
Website	Side-effect self-management	A website containing strategies to self-manage common AET side effects including; arthralgia, fatigue, vulvovaginal symptoms, gastrointestinal symptoms, hot flushes, sleep difficulties. The website uses a rating system to summarise the strength of evidence for each strategy.

Key: ROSETA= Refining and Optimising a behavioural intervention to Support Endocrine Therapy Adherence. SMS= Short Message Service. AET= adjuvant endocrine therapy. ACT= Acceptance and commitment therapy.