SBRT Enhances Quality of Life but Shows Less DFS Benefits vs MH-IMRT
A recent study published in JAMA highlights findings from the phase 3 NRG-GU005 randomized clinical trial, which evaluated the efficacy of stereotactic body radiation therapy (SBRT) against moderately hypofractionated intensity-modulated radiation therapy (MH-IMRT) in patients with favorable intermediate-risk prostate cancer. This research focused on comparing outcomes related to quality of life and disease-free survival (DFS).
The trial included 698 patients with untreated, localized intermediate-risk prostate cancer, defined as clinical stage T1-T2b with specific Gleason scores and prostate-specific antigen levels. Participants were randomly assigned to receive either SBRT (36.25 Gy in five fractions) or MH-IMRT (either 70 Gy in 28 fractions or 60 Gy in 20 fractions). The primary endpoints assessed were HRQOL, specifically bowel and urinary irritative/obstructive functions, at two years and DFS at three years.
The findings revealed that SBRT significantly improved patient-reported bowel HRQOL, with fewer patients experiencing a minimal clinically important decline (MCID) compared to those who received MH-IMRT (34.9% versus 43.8%, P = .03). However, there was no statistically significant difference in MCID rates for urinary irritative/obstructive quality among the two groups (35.4% vs. 33.7%, P = .68).
Urinary incontinence after one and two years of treatment, as well as sexual function at the one-year mark, showed better outcomes in patients treated with SBRT. Additionally, SBRT was associated with a lower incidence of grade 3 or higher genitourinary adverse events compared to MH-IMRT (0.6% vs. 2.5%, P = .04).
Despite these quality-of-life benefits, SBRT did not demonstrate superior DFS. At 3 years, the DFS rate was 88.6% for patients receiving SBRT compared with 92.1% for those receiving MH-IMRT. Furthermore, SBRT patients encountered a higher rate of biochemical failure by PSA testing (7.8% vs. 4.2%, P = .04).
These findings align with previous research from the PACE-B trial and suggest that while SBRT offers some quality of life benefits with potentially lower toxicity, longer follow-up and further studies are needed. These studies may determine whether increased dosing or advanced imaging techniques could enhance the oncologic outcomes for SBRT while preserving its benefits. The researchers emphasized the importance of continued examination to optimize prostate cancer treatments for improved patient outcomes.