In the international phase III NRG-GU005 trial, stereotactic body radiotherapy (SBRT) improved bowel-related quality of life vs moderately hypofractionated intensity-modulated radiotherapy (IMRT) in patients with favorable intermediate-risk prostate cancer. However, Ellis et al reported in JAMA that SBRT did not improve urinary irritative/obstructive–related quality of life or demonstrate superior cancer control.
“The treatment of prostate cancer with radiotherapy is evolving. How quickly radiotherapy can be delivered, and the relative risks and benefits of such a treatment, is of significant public interest,” the investigators wrote. “This study has immediate impact on patients and physicians considering a shorter course of radiotherapy for localized prostate cancer.”
Study Details
NRG-GU005 accrued patients with localized prostate cancer across 136 centers in Asia, Canada, Europe, and the United States. Eligible patients had clinical stage T1 to T2b disease with a Gleason score of 3 + 4 (Grade Group 2) and a prostate-specific antigen (PSA) level of less than 20 ng/mL or a Gleason score of 3 + 3 (Grade Group 1) and a PSA level of 10 to 20 ng/mL.
A total of 698 patients (median age = 68 years) were randomly assigned in a 1:1 ratio to receive SBRT at 36.25 Gy in 5 fractions (n = 353) or moderately hypofractionated IMRT at 70 Gy in 28 fractions or 60 Gy in 20 fractions (n = 345).
The primary outcomes of the trial were minimal clinically important declines in the Expanded Prostate Cancer Index Composite–26 Item (EPIC-26) urinary irritative/obstructive and bowel domains at 2 years and disease-free survival at 3 years. Follow-up data were provided for a median of 3.2 years.
Key Findings
At 2 years, urinary irritative/obstructive–related quality-of-life outcomes were not found to differ between the SBRT and moderately hypofractionated IMRT groups (35.4% vs 33.7%; P = .68). Outcomes for urinary incontinence at 1 and 2 years and sexual function at 1 year appeared to favor SBRT. Grade 3 or 4 genitourinary adverse events were less frequent with SBRT than with moderately hypofractionated IMRT (0.6% vs 2.5%; P = .04). Fewer patients experienced a decline in bowel-related quality of life with SBRT vs moderately hypofractionated IMRT (34.9% vs 43.8%; P = .03).
The 3-year disease-free survival rate was 92.1% (95% confidence interval [CI] = 88.9%–95.2%) with moderately hypofractionated IMRT vs 88.6% (95% CI = 85.2%–92.1%) with SBRT (one-sided log-rank P < .001 for futility). The biochemical disease–free survival failure rate by PSA testing was higher with SBRT (7.8% vs 4.2%; P = .04).
“SBRT did not result in improved urinary irritative/obstructive–related quality of life compared with moderately hypofractionated IMRT at 2 years but did improve bowel-related quality of life,” the investigators concluded. “SBRT was not superior to moderately hypofractionated IMRT in terms of cancer control at 3 years.”
Looking ahead, the investigators noted that future research should explore differences in SBRT techniques for prostate cancer.
Rodney J. Ellis, MD, of the University of South Florida, Tampa, is the corresponding author of the article in JAMA.
Disclosure: The study was supported by the National Cancer Institute and the Cancer Therapy Evaluation Program. For full disclosures of the study authors, visit jamanetwork.com.
