Impact of Prostate Radiotherapy on Urinary Bacterial Profiles and the Emergence of Multidrug-Resistant Organisms: A Prospective Study

Background Radiotherapy represents a major therapeutic modality for localized prostate cancer. Despite technological advances, pelvic irradiation remains associated with urinary complications including radiation cystitis and urinary tract infections (UTIs). Emerging evidence suggests that radiation may alter urinary microbiota and promote antibiotic resistance. Objective To evaluate the impact of prostate radiotherapy on urinary bacteriological profiles and the emergence of multidrug-resistant bacteria. Methods This prospective study included 120 patients treated for prostate cancer between March 2024 and February 2026 at the Radiation Oncology Department of Hassan II University Hospital, Fez. All patients received 3D conformal radiotherapy with or without androgen deprivation therapy. Urine cultures and antibiograms were performed before radiotherapy, weekly during treatment, and during follow-up at 1, 3 and 6 months. Infection rates and antibiotic resistance profiles were analyzed. Results Urinary infection incidence was 24% before radiotherapy, 18% during treatment, and increased to 40% after treatment. Escherichia coli (48%) and Enterococcus faecalis (32%) were the most common pathogens before radiotherapy. Multidrug-resistant bacteria increased from 10% before treatment to 28% after radiotherapy. Multivariate analysis identified radiotherapy as the only independent factor significantly associated with the emergence of resistant strains (p < 0.01). Conclusion Prostate radiotherapy significantly modifies the urinary bacteriological ecosystem and promotes the emergence of multidrug-resistant organisms. Systematic microbiological monitoring is recommended during and after radiotherapy.