Mediation analysis of adherence to pelvic floor muscle training and weekly self-monitoring on urinary symptoms in men with localized prostate cancer

INTRODUCTION: Men treated curatively for localized prostate cancer often experience urinary complications that impair quality of life. The Prostate Cancer-Patient Empowerment Program (PC-PEP) is a six-month, digital intervention integrating pelvic floor muscle training (PFMT), fitness, nutrition, and intimacy support. While early initiation of PC-PEP improves urinary outcomes, the influence of adherence remains unclear. This mediation analysis examined whether reported PFMT duration and engagement with self-monitoring mediate the association between timing of PC-PEP delivery (early vs. late) and urinary outcomes. METHODS: In a randomized, crossover trial, 128 men with localized prostate cancer were assigned to receive PC-PEP immediately (early group, n=66) or after six months of standard care (late group, n=62). Urinary outcomes were assessed using the Expanded Prostate Cancer Index Composite (EPIC) and International Prostate Symptom Score (IPSS). Weekly compliance surveys tracked engagement. Mediation and moderated mediation analyses adjusted for age, comorbidity, treatment modality, and baseline urinary function. RESULTS: Mean reported weekly PFMT duration did not differ between groups. The early group had higher compliance survey completion (98.8% vs. 64.1%, p