TOPLINE

In a randomized trial of men with intermediate-risk prostate cancer, stereotactic body radiotherapy (SBRT) improved bowel-related quality of life vs moderately hypofractionated intensity-modulated radiation therapy (IMRT). But it offered no advantage in terms of 3-year disease-free survival.

METHODOLOGY

• SBRT allows patients with prostate cancer to have a shortened radiotherapy course (typically five treatments over 2 weeks). The phase 3 NRG-GU005 trial was designed under the hypothesis that SBRT would also improve patient quality of life and disease-free survival relative to moderately hypofractionated IMRT.
• The trial enrolled patients at 136 centers in Asia, Europe, and North America from November 2017 to June 2022. A total of 698 patients (median age, 68 years) with localized intermediate-risk prostate cancer were randomly assigned in a 1:1 ratio to receive either SBRT (36.25 Gy in five fractions) or IMRT (70 Gy in 28 fractions or 60 Gy in 20 fractions).
• Primary outcomes were disease-free survival at 3 years and quality of life at 2 years, assessed by the frequency of minimal clinically important decline in the urinary irritative or obstructive and bowel domains of the EPIC-26 patient-reported survey.
• IMRT or related techniques with image guidance were required; rectal spacing was used in 55.6% of patients, rectal balloon alone in 1%, both in 3.2%, and neither in 40.3%.

TAKEAWAY

• At 2 years, there was no significant difference between the SBRT and IMRT groups in the proportion of patients with minimal clinically important decline in urinary irritative or obstructive-related quality of life (35.4% vs 33.7%; P = .68).
• Fewer patients in the SBRT arm had clinically important declines in bowel-related quality of life at 2 years: 34.9% vs 43.8% of patients in the IMRT arm (P = .03).
• However, disease-free survival at 3 years was lower with SBRT than with IMRT (88.6% vs 92.1%; hazard ratio [HR], 1.38; P < .001 for futility).
• In addition, biochemical failure rates at 3 years were higher with SBRT vs IMRT (7.8% vs 4.2%; adjusted HR, 1.82; P = .046). But patients receiving SBRT had fewer grade 3 or 4 genitourinary adverse events (0.6% vs 2.5%; P = .04).

IN PRACTICE

The finding that SBRT was better in terms of some quality-of-life outcomes, but not disease control, “has immediate impact on patients and physicians considering a shorter course of radiotherapy for localized prostate cancer,” the study authors wrote. An accompanying editorial noted that both SBRT and hypofractionated IMRT are now well-established options, and radiologists have many tools — including dose selection, image guidance, and treatment margins — to tailor treatment for individual patients.

“Ultimately, the most important message emerging from NRG-GU005 may be that optimizing prostate cancer outcomes requires attention to a constellation of treatment parameters rather than a singular focus on fractionation schedule,” the editorialists of the study wrote.

SOURCE

The study, led by Rodney J. Ellis, MD, of the University of South Florida in Tampa, Florida, was published online in JAMA.

LIMITATIONS

The trial was designed to test superiority rather than noninferiority of SBRT compared with moderately hypofractionated IMRT for disease-free survival. The protocol-defined SBRT did not explore focal radiation dose escalation and prioritized dose uniformity over higher doses to prostate tissue than those used in other studies. Quality-of-life and toxicity data were limited to 2 years of follow-up.

DISCLOSURES

The trial was supported by the National Cancer Institute. Several authors disclosed financial relationships with AstraZeneca, Astellas Pharma, Bayer, Boston Scientific, and other companies. Full disclosures are noted in the original article.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.