Given the relative novelty of stereotactic body radiation therapy as a treatment modality low-risk and intermediate-risk prostate cancer, little data exist evaluating dosimetry and its impact on patient-reported quality of life (PR-QOL) metrics. Herein, we present an interim analysis of a phase II clinical trial of PR-QOL and dosimetric correlates.
Patients with biopsy-proven low-risk or intermediate-risk prostate cancer, prostate volume ≤100 cm3, and life expectancy ≥10 years were enrolled. Expanded Prostate Cancer Index Composite (EPIC) scores were tabulated by domain and evaluated in relation to dosimetry. Paired t test was performed to compare differences in scores from baseline. Minimally important differences were established using the anchor-based approach and correlations made using the χ2 test.
A total of 95 patients were analyzed with a median follow-up of 18.1 months (range, 3.0 to 76.9 mo). There were no cases of acute or late grade 3+ GI or GU toxicities. Expanded Prostate Cancer Index Composite scores in urinary obstructive/irritative domain at 1 month (−4.8, P=0.03) and bowel domain at 1, 6, and 12 months (−10.8, −6.1, and −5.2) were significantly different from pretreatment, with both returning to nonsignificant differences around 24 months. Higher bladder V37Gy (≥3.35%) was associated with both late urinary incontinence and obstructive/irritative declines. Both higher rectal D5% and rectal V36Gy >0.6 cm3 were correlated with an enhanced proportion of patients with late minimally important difference declines.
Higher dose volumes for the bladder and rectum predicted for poorer PR-QOL. In contrast to prostate brachytherapy data, neither prostate volume nor urethral dosimetry at this dose schedule correlated with urinary symptoms.
*University of Pittsburgh School of Medicine
†Department of Radiation Oncology, UPMC Hillman Cancer Center, Pittsburgh, PA
‡East Coast Radiation Oncology, Toms River, NJ
The authors declare no conflicts of interest.
Reprints: Dwight E. Heron, MD, MBA, FACRO, FACR, Department of Radiation Oncology, UPMC Hillman Cancer Center, 5230 Centre Avenue, Suite 544, Pittsburgh, PA 15232. E-mail: email@example.com.
Online date: October 3, 2019