Comparison of Stereotactic Body Radiotherapy with Conventional or Low-Fraction Radiotherapy for Patients with Low/Intermediate-Risk Localized Prostate Cancer

To demonstrate whether Stereotactic Body Radiotherapy (SBRT) is not inferior to conventionally or moderately hypo- fractionated radiotherapy (fewer treatments with more radiation delivered with each treatment) regimens for PSA and/or clinical failurefor localized prostate cancer, researchers undertook a clinical trial, called “PACE-B” They enrolled me with stage T1-T2 prostate cancer, Gleason score less than or equal to 3+4, and PSA less than or equal to 20 ng/mL and randomized them to receive SBRT (36.25 gray [Gy] in 5 fractions over 1-2 weeks) or control radiotherapy (CRT) (78Gy/ fractions over 7.5 weeks, or 62Gy/20 fractions over 4 weeks). It is noteworthy that they did not permit the use of hormonal therapy, which is sometimes also used in such patients, and enhances the response to radiation in higher-risk patients. The primary endpoint was the proportion who remained free from PSA or clinical evidence of treatment failure. To call SBRT non-inferior, the failure rate had to be no more than 1.45 times higher than that of CRT.

They randomized 874 patients from 38 centers (CRT=441, SBRT=433) between August 2012 and January 2018. Their median age was 69.8 years, median PSA 8.0 ng/mL, NCCN (National Comprehensive Cancer Network) risk group was 9.3% low, 90.7% intermediate. The 5-year biochemical/clinical failure-free rate was 94.6% for CRT vs 95.8% for SBRT. Thus, SBRT was not inferior to CRT. However, moderate urinary side effects were more common with SBRT, and the gastrointestinal side effects were virtually the same in both groups.

N Engl J Med. 2024 October 16; 391(15): 1413–1425