Hypofractionated Image-Guided Radiotherapy (IGRT) With Organ Motion Mitigation and Urethral Sparing for Prostate Cancer

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The present study evaluates the safety, feasibility, quality-of-life effects, PSA kinetics, and clinical outcomes of definitive dose-escalated external beam radiotherapy for localized adenocarcinoma of the prostate. Eligible patients will have biopsy-proven localized prostate adenocarcinoma without radiographic evidence of regional or distant metastases and without MRI evidence of radiographic T3/T4 disease. Patients may have low-risk, intermediate-risk, or selected high-risk disease. Previous or concomitant hormonal therapy is allowed but is not required, provided prior hormonal therapy was not given for more than 6 months before protocol therapy. Patients enrolled in the study will receive image-guided volumetric modulated arc radiotherapy (IGRT-VMAT) to 45 Gy in five fractions of 9 Gy each, delivered on five consecutive treatment days unless a clinically or operationally justified interruption is required. Treatment will use organ-motion mitigation, urethral localization, online target tracking, urethral sparing, and treatment-planning quality assurance procedures designed to support normal tissue sparing and accurate radiation delivery. A rectal balloon with air filling will be used for prostate immobilization and anatomical reproducibility, and a urethral catheter loaded with beacon transponders will be used for set-up reproducibility and online tracking. Patients will be followed at approximately 1 month after treatment, then at approximately 3, 6, 9, and 12 months, and every 6 months thereafter through 60 months. Patients will be followed for a minimum of 5 years. Follow-up assessments will include physician-graded gastrointestinal and genitourinary toxicity using NCI CTCAE v4.0, patient-reported urinary, bowel, and sexual quality-of-life outcomes using validated instruments including EPIC, IPSS, and IIEF questionnaires, and serum PSA testing. Biochemical relapse-free survival will be assessed using the Phoenix definition, and recurrence patterns will be summarized from clinically indicated imaging.