Phase 1/2 Study on Stereotactic Hypofractionated Once-Weekly Radiation Therapy for Nonmetastatic Prostate Cancer

Abstract

Purpose/Objective(s): Stereotactic radiotherapy has shown promising results in Phase II studies, but has been investigated predominantly in patients with low-intermediate risk disease. We conducted a clinical trial of stereotactic hypofractionated radiotherapy delivered in once-weekly fractions on patients with non-metastatic disease to test feasibility, acute toxicities, patient reported outcomes, and biochemical control in a cohort with predominantly high-risk disease. Purpose/Objective(s): Patients with prostatic adenocarcinoma, Gleason 6-10, T1-4N0 (staged with multiparametric MRI and bone scans) and PSA < 0.001) but reduced to 10.9 at 6 months (P = 0.05). Of the 21 parameters studied in the EORTC QLQ framework, only the urinary symptom score showed a clinically meaningful worsening from a mean of 20/100 at baseline to 34/100 at end of treatment (P < 0.001), but reduced to 24/100 at 6 months (P = 0.08). Other functional or symptomatic scales did not show any clinically meaningful worsening. There was 1 patient each with late grade 2 rectal bleeding and grade 2 urinary toxicity. With a median follow-up of 25 months, 1 patient developed a distant failure at 10 months, with a 2 year biochemical control rate of 96.7%. Conclusion(s): In a cohort of mainly high risk cancers in a developing country, stereotactic once-weekly radiation therapy was easy to implement, safe and well tolerated with a low incidence of acute toxicity. Preliminary biochemical control and late toxicity profiles are encouraging. This paves the way for further prospective evaluation in a larger cohort of patients with high-risk disease.