Determining individual preferences for gynecomastia avoidance among men with prostate cancer: A qualitative study.

TPS407 Background: Biochemical recurrence (BCR) affects 20–50% of men within 10 years of primary therapy for prostate cancer (PCa). The EMBARK trial demonstrated improved metastasis-free survival with Enzalutamide (ENZ), alone or in combination with ADT, compared with ADT alone. However, ENZ monotherapy introduces a side effect profile notably of gynaecomastia, nipple pain, and breast tenderness—occurring in approximately 45% of patients and causing treatment discontinuation in 16% of cases. Gynaecomastia may significantly affect men’s quality of life (QoL) due to changes in body image and associated discomfort. Previous qualitative work on breast-related symptoms in PCa is limited and largely focused on ADT-related, non-painful enlargement, without reflecting contemporary attitudes or the ENZ-specific side effect profile. As treatment options expand, understanding men’s perceptions of these side effects is critical to shared decision-making and aligning treatment strategies with patient preferences. Discrete choice experiments (DCEs) are an established method to quantify treatment preferences by identifying trade-offs between attributes such as efficacy, toxicity, and QoL. To inform a future DCE on treatment preferences, qualitative work is needed to explore men’s perceptions of breast-related side effects, their impact, and the acceptability of prophylactic measures such as tamoxifen. Methods: This qualitative study will use semi-structured interviews to explore men’s experiences and perceptions of gynaecomastia related to BCR PCa treatments, forming the basis for the development of DCE attributes and levels in a subsequent study. Purposive sampling will be used to recruit two groups: (1) men with BCR PCa without prior ADT/ENZ exposure, and (2) men with prior ADT/ARPI exposure who have experienced breast-related side effects. Approximately 10–12 participants per group (20–24 total) will be recruited, with final sample size determined by information power. Interviews will be conducted via telephone or videoconference, lasting approximately 30 minutes. Topics will include perceptions of QoL impacts, breast-related symptoms (hypothetical or experienced), attitudes towards prophylaxis, and the impact on body image and treatment decision-making. Interviews will be audio-recorded, transcribed verbatim, and analysed using NVivo. Demographic and clinical data (age, years since diagnosis, treatments received) will be collected. To mitigate risk of distress, participants will be informed of sensitive topics in advance, retain the right to skip questions or withdraw, and a distress protocol will be in place. Verbal informed consent will be recorded prior to interviews to minimise collection of identifying information. This study will generate foundational qualitative data to support patient-centred approaches to BCR PCa treatment decision-making. Clinical trial information: ACTRN12625001210460p.