Does Stereotactic Body Radiotherapy Offer Benefit in Localized Prostate Cancer?

Patients with low- to intermediate-risk prostate cancer have a number of potential management options including active surveillance (primarily for low-risk cancer) and surgery or radiotherapy with curative intent. Improvements in radiotherapy technology have enabled 5-fraction stereotactic body radiotherapy (SBRT), which involves administering higher biologic doses per treatment session in fewer total sessions with the goal of reducing therapy-related toxicity while maintaining efficacy.

Investigators conducted an open-label, randomized, phase 3, noninferiority trial in men with clinical stage T1/T2 prostate cancer with a Gleason score of 3+4 or less who had prostate-specific antigen (PSA) values ≤20 ng/mL. Participants received standard-of-care radiotherapy (using one of two standard treatment regimens) or SBRT in 5 fractions. The primary endpoint was freedom from biochemical (PSA) or clinical failure. Median age of the 874 participants was 70 years; 8.4% had low-risk and 91.6% intermediate-risk cancer.

Among the key findings:

• Clinical characteristics were well balanced between treatment arms.
• At a median follow-up of 74 months, SBRT was noninferior to control radiotherapy; 5-year incidence of freedom from biochemical/clinical failure was 95.8% with SBRT and 94.6% with control radiotherapy.
• A post hoc test for superiority was not significant.
• The incidences of late Radiation Therapy Oncology Group (RTOG) grade 2 or higher genitourinary and gastrointestinal toxic effects were 26.9% and 10.7%, respectively, with SBRT and 18.3% and 10.2% with control radiotherapy.