Partial Prostate Salvage High Dose Rate Brachytherapy

Overview

A dose-response relationship for radiation in the management of prostate cancer is well established. Local recurrence of prostate cancer after external beam radiotherapy occurs in at least 40% of patients treated because of inability to deliver sufficient dose through external beam techniques. These patients respond well to re-irradiation using brachytherapy with about 50% of selected patients remaining free of recurrence 5 years after salvage. Advanced imaging using multiparametric Magnetic Resonance Imaging (mpMRI) allows identification of the site of recurrence, permitting partial prostate salvage brachytherapy. There is extensive literature on Low Dose Rate salvage brachytherapy but less on High Dose Rate.

Appropriately selected patients with histologically documented recurrence 3 years or more after initial external beam radiotherapy will undergo mpMRI for identification of the site of recurrence. A planning transrectal ultrasound (TRUS) will be obtained for fusion with the mpMRI and transposition of the target volume (GTV=gross tumor volume). A margin of 4.5 cm will be added to the GTV to create a focal planning target volume (PTV). The margin may be cropped at the interface with critical organs. Two fractions of HDR brachytherapy will be delivered, each from a single implant, 2 weeks apart. Following treatment patients will be monitored for toxicity and quality of life using the Expanded Prostate cancer Index (EPIC) questionnaire as well as the International Prostate Symptom score. Efficacy will be evaluated by monitoring the Prostate Specific Antigen (PSA) and if PSA is rising during follow-up, PSMA PET will be ordered when clinically indicated..