Exploring trial acceptability, recruitment, and retention in a pilot optimisation randomised controlled trial of a behavioural intervention to support medication adherence in women with breast cancer: A qualitative process evaluation.

BACKGROUND: Complex factorial trials are increasingly employed to optimise complex behavioural interventions. However, acceptability of such designs to participants are unknown. In this qualitative process evaluation of a pilot optimisation randomised controlled trial (O-RCT) for a behavioural intervention to support medication adherence in women with breast cancer, we explored acceptability of trial participation, alongside barriers and facilitators to recruitment and retention. METHODS: We conducted a 2 4-1 fractional factorial pilot O-RCT evaluating the feasibility of four intervention components aiming to support adherence to adjuvant endocrine therapy in women with breast cancer. 52 women were randomised to one of eight conditions, comprising unique intervention component combinations. Four-months post-randomisation, 20 participants completed a semi-structured interview guided by the Theoretical Framework of Acceptability (TFA) and Theoretical Domains Framework (TDF). Data were analysed using rapid qualitative analysis and findings were mapped onto TFA and TDF constructs. RESULTS: Generally, participation in the trial was perceived positively ( affective attitude). Most women reported easy participation ( burden), confidence in capabilities ( self-efficacy, beliefs about capabilities), minimal opportunity costs ( opportunity cost), and personal benefit from participation ( perceived effectiveness, knowledge, beliefs about consequences). Randomisation process understanding ( coherence), and questionnaire retention experiences were mixed; women reported reduced motivation to complete questionnaires due to length, repetitiveness, and emotional impact ( motivation and goals, memory, attention, and decision processes) . Participation decisions were shaped by contextual factors, ( environmental context and resources), altruism, personal benefit, and wanting to advance science ( social/professional role and identity, motivation and goals). CONCLUSIONS: This qualitative process evaluation suggests participation in an O-RCT was acceptable. Low randomisation coherence and questionnaire burden are notable areas for improvement. Future studies within trials should explore approaches to explaining factorial trials to participants. Barriers and facilitators to recruitment and retention were similar to parallel group randomised trials, suggesting interventions addressing these may be applicable regardless of trial design.