NRG-GU005: five-fraction SBRT spared bowel function and continence better than IMRT, but did not improve disease control

Design

Phase 3, international, open-label randomised trial (NRG-GU005)

Population

698 men with localised intermediate-risk prostate cancer

Primary outcome

EPIC-26 urinary and bowel decline at 2 years; DFS at 3 years

Effect

Bowel decline 34.9% vs 43.8% (P = 0.03); 3-year DFS 88.6% vs 92.1%

NRG-GU005 randomised 698 men with intermediate-risk localised prostate cancer at 136 centres to SBRT (36.25 Gy in 5 fractions) or moderately hypofractionated IMRT (70 Gy in 28 or 60 Gy in 20). Median follow-up was 3.2 years.

Urinary irritative decline at two years did not differ (35.4% vs 33.7%). Bowel quality-of-life decline was less frequent with SBRT (34.9% vs 43.8%, P = 0.03), and continence and one-year sexual function favoured SBRT. Grade 3–4 genitourinary events were fewer (0.6% vs 2.5%). Three-year disease-free survival was 88.6% with SBRT and 92.1% with IMRT; SBRT was not superior.

Five fractions instead of 20–28 is a large gain in convenience and, here, in bowel function. But the trial was designed to show SBRT better on disease control, and it was not. Longer follow-up will matter.

• Offer SBRT as an option for intermediate-risk disease where the expertise exists.
• Discuss the quality-of-life advantage and the absence of a disease-control advantage.
• Continue moderately hypofractionated IMRT as a standard.
• For patients travelling long distances — common in India — five fractions may weigh heavily.

Why it matters

It confirms SBRT is kinder, which moves the decision to convenience and patient preference.

Don't overread it

Not superior on disease-free survival is not the same as proven equivalent; three years is short for prostate cancer.

The statistics, in plain English

The bowel difference (34.9% vs 43.8%) is about 9 fewer men in 100 with a meaningful decline. The disease-free survival figures overlap in their confidence intervals, and the trial tested for superiority, which SBRT did not show.

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