FINDINGS
A study led by UCLA Health Jonsson Comprehensive Cancer Center investigators found that stereotactic body radiotherapy (SBRT), a form of high-dose radiation delivered in just five sessions, after prostate surgery is safe and as effective as traditional, longer courses of radiation in preventing prostate cancer from returning.
After more than four years of follow-up, researchers found:
- 60% of patients remained free of biochemical recurrence, meaning there were no signs of cancer or rise in PSA, and no need for additional hormone therapy.
- SBRT without hormone therapy lowered the risk of recurrence compared to conventional radiation.
- Side effects were generally manageable. Serious bowel problems occurred in 7% of patients, and urinary issues in 32%. Using MRI-guided radiation helped reduce urinary side effects even further.
- Most patients maintained their quality of life, with minimal changes in urinary, bowel and sexual health.
BACKGROUND
After prostate surgery, some men remain at risk of their cancer coming back. Radiation therapy can lower this risk, but the standard approach usually involves daily treatments for several weeks, which can be burdensome for patients. Researchers have been exploring whether SBRT, already a proven option for men who have not had surgery, could also be safe and effective in the post-surgery setting. Its use has been limited, however, because of concerns about safety and the sensitivity of nearby organs.
METHOD
The SCIMITAR Phase 2 trial enrolled 100 patients at UCLA and the University of Southern California who had undergone a radical prostatectomy and were considered at higher risk of recurrence. Patients received SBRT in five sessions over roughly 10 days, with some also receiving hormone therapy or lymph node radiation based on physician guidance. Patients were then monitored for about 4.5 years for cancer recurrence, side effects and quality of life.
IMPACT
These results build on earlier findings, which showed SBRT is safe and convenient over a two-year period. Together, the studies suggest that SBRT may be a faster, simpler option for men who need radiation after prostate surgery.
“These findings suggest this faster treatment approach could offer an alternative to conventional, longer radiation courses for men at risk of recurrent prostate cancer,” said co-first author Dr. Amar Kishan, professor and executive vice chair of radiation oncology at the David Geffen School of Medicine at UCLA and co-director of the cancer molecular imaging, nanotechnology and theranostics program at the UCLA Health Jonsson Comprehensive Cancer Center. “Importantly, side effects were manageable in a majority of men, particularly with MRI-guided treatment, and most men were able to maintain their quality of life.”
JOURNAL
The study was published in the journal European Urology and presented at the 2025 American Society for Radiation Oncology (ASTRO) Annual Meeting.
AUTHORS
Dr. Kishan is the study's co-first author. Dr. Jesus Juarez Casillas, co-chief resident in the department of radiation oncology at UCLA, is the other co-first author. The senior author is Dr. Michael Steinberg, professor and chair of radiation oncology at the David Geffen School of Medicine at UCLA and director of Clinical Affairs at the UCLA Health Jonsson Comprehensive Cancer Center. Other UCLA authors are Tahmineh Romero Kalbasi, Ankush Sachdeva, John Nikitas, Danielle Karasik, Luca Valle, Kekoa Taparra, Robert Reiter, Christopher Saigal, Karim Chamie, Nicholas Donin, Arnold Chin, Matthew Rettig, Nicholas Nickols and James Lamb. A full list of authors can be found here.
FUNDING
The study was supported in part by grants from the National Institutes of Health Prostate Cancer Specialized Programs of Research Excellence and the U.S. Department of Defense.
Journal
European Urology