KEY POINTS
- SRAM was a single-centre, open-label, randomized phase II trial including 121 patients with node-negative high-risk prostate cancer. All received 18–24 months of androgen deprivation therapy.
- Patients received either once-weekly SBRT delivering 40 Gy in 5 fractions to the prostate, 36.25 Gy in 5 fractions to the seminal vesicles, and 25 Gy in 5 fractions to the pelvis, or conventional IMRT delivering 76 Gy in 38 fractions, including 50 Gy in 25 fractions to the prostate and pelvis.
- Acute grade ≥2 gastrointestinal toxicity occurred in 8.3% with SBRT versus 39.0% with IMRT (p<0.0001). Acute grade ≥2 genitourinary toxicity was 23.3% versus 36.1%, respectively (p=0.126).
- One grade 3 gastrointestinal event, diarrhea, occurred in the IMRT arm. No grade 3 genitourinary events were reported.
- At 1 week, clinically meaningful deterioration in EPIC bowel scores occurred in 29% with SBRT versus 62% with IMRT (p=0.0002), while urinary deterioration occurred in 58% versus 77% (p=0.0232). Differences were largely transient, with scores converging by 3 months.
CLINICAL TAKEAWAY
Once-weekly prostate-and-pelvis SBRT produced substantially less acute gastrointestinal toxicity than conventionally fractionated IMRT, with no statistically significant increase in genitourinary toxicity. This is an important randomized phase II safety signal, but it is not yet practice-changing: the analysis was single-centre, follow-up for the reported outcomes was limited to 3 months, prostate PTV margins differed between arms, and late toxicity and oncologic efficacy remain unknown.
SOURCE
International Journal of Radiation Oncology, Biology, Physics