Shorter radiation treatment after surgery found safe for prostate cancer patients

For men who undergo a radical prostatectomy for the treatment of prostate cancer, post-surgery radiation therapy can play a vital role in reducing the risk of recurrence. Despite its benefits, many patients decline or defer radiation because it requires daily sessions for several weeks. 

Now, a new study published in JAMA Oncology and led by UCLA Health Jonsson Comprehensive Cancer Center investigators suggests there may be a faster option. Researchers found that stereotactic body radiotherapy (SBRT), a form of high-dose radiation delivered in just five sessions, is as safe as conventional treatment, with similar side effects and a similar impact on quality of life. 

This approach could remove a major barrier to post-surgery radiation therapy. SBRT shortens treatment time, reduces healthcare costs, and may have biological advantages in targeting prostate cancer. UCLA has long been a pioneer in SBRT for treating patients who have not yet had surgery, and now with the SCIMITAR trial, we have the first phase II data in the world to support this treatment in men who have had surgery." 

Dr. Amar Kishan, executive vice chair of radiation oncology, David Geffen School of Medicine at UCLA and senior author of the study

SBRT is a well-established treatment for prostate cancer, offering strong long-term control with minimal side effects. However, its use after a radical prostatectomy-a common surgery to remove the prostate gland-has been limited due to concerns about the shifting position of the prostate bed and nearby healthy tissues. As a result, only a few clinical trials have explored SBRT in the post-surgery setting, despite its potential benefits. Significant improvements in radiation delivery, including newer MRI-guided radiation therapy that provides clearer images and real-time tracking, have led to increased comfort with exploring post-surgery SBRT. 

To better understand the feasibility of SBRT in this setting, researchers conducted a study called SCIMITAR to investigate whether these advancements could make SBRT a viable option for post-surgery patients.

The study followed 100 men who received SBRT after radical prostatectomy for over two years. During this time, the researchers tracked patients' urinary, bowel, and sexual health, comparing outcomes to 200 patients who underwent conventional radiation.

The researchers found SBRT did not cause more side effects than standard treatment. About 25% of patients experienced moderate urinary issues and 4% had severe symptoms. For bowel issues, 3% had moderate issues and 3% had severe symptoms, rates consistent with those seen in conventional radiation. 

Patients who received SBRT reported no significant differences in quality of life compared to those who had conventional radiation, even after two years.

The study also found that MRI-guided SBRT reduced gastrointestinal and late genitourinary side effects even further, suggesting that newer imaging techniques could make the treatment even safer.

"We attribute this difference to primarily the narrower planning margin (3mm vs 5mm), which in turn we were confident using because of the more accurate daily setup imaging and improved motion management with gating," said Kishan, who is also an investigator in the UCLA Health Jonsson Comprehensive Cancer Center. 

The researchers caution that longer-term studies are needed to confirm SBRT's effectiveness. The UCLA-led EXCALIBUR trial is expected to provide more data on its long-term impact. An update on SCIMITAR, focusing on cancer control rates, is planned for later this year.

"This study is a crucial step toward making prostate cancer treatment more accessible to patients," said study co-author 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. "We're optimistic that shorter, more convenient radiation schedules will improve care and quality of life for men with prostate cancer."

The study's first author is Dr. John Nikitas, a resident in the department of radiation oncology at UCLA Health. Other UCLA authors are Tahmineh Romero, Dr. Luca F. Valle, Ankush Sachdeva, Natalie Chong, Vince Basehart, Antonio Franco, Dr. Robert Reiter, Dr. Christopher Saigal, Dr. Karim Chamie, Dr. Mark S. Litwin, Dr. Nicholas M. Donin, Dr. Matthew Rettig, Dr. Nicholas G. Nickols and Minsong. A full list of authors is included with the article.

The study was supported in part by grants from the National Institutes of Health and the Department of Defense.