Early Outcomes of Stereotactic Body Radiotherapy for Localized Prostate Cancer: A Retrospective Analysis.

BACKGROUND: Prostate cancer is the most common cancer in US males. While conventional beam radiotherapy has been commonly used, there has been a shift toward hypofractionation, which involves using fewer higher-dose fractions over a shorter treatment course. Stereotactic body radiotherapy (SBRT) further condenses treatment to 5 fractions in < 2 weeks. METHODS: This was a retrospective chart review of a veteran population with localized prostate cancer who received SBRT between November 2014 and October 2024 at the Kansas City Veterans Affairs Medical Center. Androgen deprivation therapy (ADT) or pelvic nodal irradiation with ADT was administered where indicated. Patients were included and followed for at least 24 months to assess efficacy and genitourinary (GU) and gastrointestinal (GI) toxicity using Radiation Therapy Oncology Group (RTOG) criteria. Cone-beam computed tomography was exclusively used for image-guided radiotherapy without the use of fiducials or hydrogel spacers. RESULTS: A total of 174 patients met the inclusion criteria. The median age was 74 years, and the median prostate-specific antigen level was 11.9 ng/mL. Twenty-six patients had a Gleason score (GS) of 1, 77 had GS 2, 41 had GS 3, 18 had GS 4, and 12 had GS 5. Patients had a median follow-up of 45 months, and the disease-free survival and overall survival rates were 96.6% and 99.4%, respectively. There were 6 biochemical failures (3.4%), with 1 patient dying from metastatic cancer. The cumulative RTOG grade II and higher GU toxicity was 28.2% (26.4% grade II, 1.2% grade III, and 0.6% grade IV toxicity with rectovesical fistula requiring surgery). The cumulative RTOG grade II or higher GI toxicity rate was 3.4% with no grade III or IV complications. CONCLUSIONS: This retrospective analysis indicates that a short course of SBRT for localized prostate cancer demonstrates acceptable toxicity and promising early efficacy, even without the use of fiducials or hydrogel spacers. Longer follow-up is warranted to confirm these findings.