# Robotic Stereotactic Body Radiation Therapy for High-Risk Prostate Cancer: The Georgetown University Experience

## TL;DR

This study shows that robotic SBRT is a safe and effective treatment for high-risk prostate cancer, with good cancer control and minimal impact on quality of life.

## Contribution

The study provides long-term quality of life and cancer control data for high-risk prostate cancer patients treated with robotic SBRT.

## Key findings

- Three-year biochemical disease-free rate was 89% in high-risk prostate cancer patients treated with robotic SBRT.
- Most recurrences were bone metastases, followed by PSA-only recurrences and local or lymph node involvement.
- Quality of life scores remained largely stable or improved after treatment, with minimal clinically significant decline.

## Abstract

Introduction

Stereotactic body radiation therapy (SBRT) has emerged as a highly conformal and hypofractionated treatment modality, demonstrating safety and efficacy in low- and intermediate-risk prostate cancer (PCa). Traditionally, high-risk (HR) PCa has been managed with conventional fractionation external beam radiotherapy. Such extended treatment may be burdensome to elderly PCa patients. There is a dearth of long-term patient-reported outcome data for HR PCa patients treated with SBRT. This retrospective study examines cancer control and health-related quality of life (HRQOL) outcomes in HR PCa patients receiving robotic SBRT.

Materials and methods

HR PCa patients who underwent robotic SBRT treatment (7-7.25 Gy in five fractions over one to two weeks) from December 2008 to July 2023 were included in this retrospective analysis. Biochemical failure was defined according to the Phoenix criteria as a rise in PSA of ≥2 ng/mL above the nadir. Patterns of failure were classified as PSA only, local, pelvic node, abdominal node, or bone. Patients completed the 26-item expanded PCa index composite (EPIC)-26 questionnaire at baseline, three, six, 12, 18, 24, and 36 months post radiotherapy. HRQOL domain scores for urinary incontinence, urinary irritative/obstructive, and bowel function were calculated following EPIC-26 scoring guidelines, with higher scores indicating improved quality of life (QOL). Kruskal-Wallis tests and Post-Hoc Dunn Multiple Comparison Tests were employed to examine significant changes within HRQOL domains. Minimally important differences were calculated using 0.5 of a standard deviation at baseline.

Results

A total of 216 patients, with a median age of 75 years, completed the treatment and had a median follow-up of 40 months. Seventy-five percent of patients received androgen deprivation therapy prior to radiotherapy initiation. The three-year biochemical disease-free rate was 89%. Among all recurrences, bone metastases were the most common (34.15%), followed by PSA-only recurrences (24.39%), local recurrences (17.08%), and abdominal and pelvic lymph node involvement (12.2% each). At the initiation of RT, patients exhibited a urinary incontinence domain score of (mean ± SD) 86.04 ± 1.27, a urinary irritative/obstructive domain score of 83.4 ± 1.06, and a bowel domain score of 92.7 ± 0.85. Three years post-treatment, the urinary incontinence domain score decreased to 84.4 ± 1.9, the urinary irritative/obstructive domain score increased to 86.3 ± 1.34, and the bowel domain score decreased to 90.63 ± 1.37. These changes did not reach statistical and/or clinical significance.

Conclusions

At the three-year follow-up mark, favorable cancer control was achieved, and patients had recovered mainly to near baseline urinary and bowel function. SBRT demonstrated excellent tolerability with minimal impact on PCa-specific HRQOL in HR PCa patients. These findings underscore the potential of SBRT as a convenient treatment option for HR PCa, offering promising outcomes and preserving patient QOL.