Comparing Preliminary Acute Toxicity between Two Recent Prospective Radiotherapy Treatments for Patients with Prostate Cancer: Reduced PTV Margins vs GTV Boost

Abstract

To compare the acute toxicity of the two clinical trials of prospective radiotherapy treatment of prostate cancer: Integrated Advanced Imaging for Treatment Planning and Guidance (Margin) study, and the Tumour-Targeted Radiotherapy (Target) study. 23 patients enrolled in the Margin study were treated using an IMRT plan with prescription dose of 78 Gy with reduced PTV margins of 3 mm to left/right and 5 mm to anterior-posterior and crania-caudal direction guided by means of daily cone beam CT (CBCT) imaging prior to treatment. A subset of patients in the Target study received only external beam radiation therapy. These 10 patients were treated using volumetric modulated arc therapy (VMAT) with a prescription dose of 76 Gy to the CTV and 95 Gy to the GTV (integrated VMAT boost). The acute toxicity for GI and GU was measured using CTCAE V4.0 toxicity assessments. Margin study showed GI toxicity of 30.43%, 60.87%, and 8.7% for grade 0, 1 and 2, respectively. GU toxicity was 4.35%, 78.26%, and 17.39%. The Target study showed a more promising preliminary result. GI toxicity in the Target study was 60.5.43%, and 37.5% for grade 0 and 1. The GU distribution showed 12.5% and 87.5% for grade 0 and 1. No grade 2 or higher toxicity was reported in Target patients. Target study showed a lower acute toxicity in both GI and GU compared to Margin study. Due to the limited sample size in both studies, however, further investigation is warranted for both acute toxicity and late toxicity with a larger sample size.