Quality of life (QOL) and acute toxicities of a pilot study of focal salvage high-dose rate (HDR) prostate brachytherapy in patients with local recurrence after definitive external-beam radiotherapy (XRT).

Abstract

79 Background: Despite dose-escalated radiotherapy, studies of post-treatment biopsies of the prostate for intermediate-risk prostate cancer suggest that approximately 20% will be positive. Salvage options include surgery, brachytherapy, cryotherapy or high-frequency ultrasound. However, the risk of significant complications (e.g. fistula, incontinence, bladder neck contracture), is not insignificant. The objective of this pilot study is to explore the QOL, toxicities and efficacy of focal salvage HDR prostate brachytherapy. Methods: This study was approved by the institution’s research ethics board. Eligible patients included: biopsy-confirmed local recurrence >30 months after XRT, MRI demonstrating solitary recurrence confined to the prostate, negative metastatic workup, IPSS <15, post-XRT PSA <10ng/mL, prostate volume ≤50cc. Salvage ultrasound-based HDR brachytherapy was performed with a prescription dose of 27Gy divided over two implants separated by 1 week to the target volume (TV) as seen on MRI with dose constraints to the urethra and rectum. Results: Eleven patients (mean age 73 years) have been enrolled in the study. At initial presentation, there were 4, 6 and 1 low-, intermediate- and high-risk disease, and initial XRT received was 70-78Gy. The Gleason score of the local recurrence was 7 and 8-10 in 6 and 5 patients, respectively. The pre-HDR mean PSA was 5.0 (range 1.3 – 9.29). The median size of the recurrence on MRI was 10mm and median volume of the TV was 5.9cc (2.2-16.1), TV V100 96.0%, urethral D10 64.5% and rectal D1cc 42.9%. Ten patients have at least 6 months of follow-up (median 10 months), and no acute GU/GI grade 3-5 toxicities were observed, including urinary retention. The most common acute toxicity was frequency and nocturia. Mean IPSS at baseline, 1-, 3- and 6-months was 6, 8, 7 and 5. At 6-months, 9 of 10 patients had a lower PSA (mean 1.78) than baseline. There was no significant change in EPIC urinary, bowel and sexual domains within the first 6-months. Conclusions: Preliminary data suggests that focal salvage HDR brachytherapy was technically feasible with minimal acute toxicities. Clinical trial information: NCT01583920.