A genetic test that reads inherited DNA may one day help men with prostate cancer decide whether a short, high-dose course of radiation is right for them. UCLA researchers are presenting data at the American Society for Radiation Oncology (ASTRO) annual meeting in Boston showing that men flagged as high risk by the test were about 36 times more likely to develop long-term urinary side effects after stereotactic body radiation therapy, or SBRT. The findings are scheduled for presentation Sept. 29, according to a UCLA Health announcement.
The question matters because most men with localized prostate cancer live many years after treatment. That makes quality of life, including bladder, bowel, and sexual function, central to the decision. Late urinary problems such as urgency, leakage and discomfort can appear months after radiation and sometimes persist. MiraDx, the company behind the test, cites earlier research showing that more than 20% of men treated with external radiation experience persistent urinary side effects.
The research is early, and it arrives alongside new trial results comparing surgery with five-session radiation. Together, they give men more to discuss with their doctors but no single new rule to follow.
Inside the UCLA Genetic Test Findings
The test, called PROSTOX, looks for inherited genetic differences that may affect how a person's tissue responds to radiation. The study was led by Dr. Amar Kishan, executive vice chair of radiation oncology at UCLA's David Geffen School of Medicine, and Dr. Joanne Weidhaas, a professor of radiation oncology at UCLA. The researchers analyzed data from four clinical trials involving 457 men who received SBRT.
Men classified as high risk were about 36 times more likely to develop late urinary side effects than those classified as low risk. In a separate prospective trial, using the test to guide treatment reduced moderate to severe urinary side effects, in part by steering high-risk men toward a longer course of radiation instead of SBRT. The work is listed as Abstract 311 in the ASTRO program.
SBRT delivers radiation in about five sessions over one to two weeks. Longer courses spread smaller doses across several weeks, which means more trips to the clinic and more time away from work. For men who are good candidates for both, knowing their likely side-effect risk could help them weigh convenience against comfort.
Surgery Versus Five-Session Radiation Gets Longer-Term Data
On Sept. 28, researchers from The Royal Marsden and The Institute of Cancer Research in London presented eight-year results from the PACE-A trial, which randomly assigned men with low- or intermediate-risk localized prostate cancer to SBRT or prostate removal surgery. The trial included 123 men. At eight years, 91.2% of men treated with SBRT and 83.7% of those who had surgery remained free of signs that their cancer had returned or progressed.
Side effects differed more clearly. At five years, 3 of 36 surveyed SBRT patients used at least one urinary pad a day, compared with 14 of 29 surgery patients.
The results show that "SBRT appears to achieve comparable long-term cancer control to surgery, helping patients make more informed decisions about their care," said Prof. Nicholas van As, the trial's chief investigator, in an Institute of Cancer Research release. The trial was small, with only 13 recurrence or progression events in total, and it was not designed to prove the two treatments are equivalent for cancer control. It was funded by Accuray and Varian, companies that make radiation equipment.
Evidence Gaps and a Financial Tie Worth Knowing
The UCLA findings are a conference presentation, not a peer-reviewed paper with full data. The public summary reports relative risk but not how many high-risk men actually developed lasting side effects. Without absolute numbers, men cannot yet judge how much the test would change their personal odds.
Men should also know that a version of the test is already sold. Weidhaas is a co-founder of MiraDx, the company that markets PROSTOX tests to patients considering SBRT and longer radiation courses. That relationship does not invalidate the research, but independent studies will matter before the test becomes routine care. Major treatment guidelines have not been updated to recommend it, and insurance coverage may vary.
Questions to Ask a Radiation Oncologist
Men with newly diagnosed localized prostate cancer typically weigh active surveillance, surgery, and several forms of radiation. Useful questions include whether active surveillance is reasonable for your cancer's risk level and whether you are a candidate for SBRT, a longer course, or both. It also helps to ask how your current urinary symptoms and prostate size affect side-effect risk.
On the genetic test specifically, men can ask whether their results would change the doctor's recommendation, what the absolute risk of side effects would be, and whether insurance covers the test. It is also reasonable to ask how the center manages urinary side effects if they occur and how many SBRT treatments it performs each year.
Anyone with blood in the urine, inability to urinate, or fever and pain after treatment should contact their care team right away. Men should not delay or switch treatment based on news reports alone, and a second opinion from a urologist or radiation oncologist can help when options seem close.
MedicalDaily previously covered shifting prostate cancer screening guidance and will follow the UCLA data if it appears in a peer-reviewed journal.
Key Questions Answered
What is the PROSTOX genetic test?
It is a test of inherited DNA that aims to identify men at higher risk of long-term urinary side effects after prostate radiation. UCLA researchers are presenting new data on it at ASTRO 2026.
What did the UCLA study find?
Across four trials involving 457 men, those classified as high risk were about 36 times more likely to develop late urinary side effects after SBRT than those classified as low risk.
Is the test part of standard care?
Not yet. A commercial version is sold, but major guidelines do not recommend it routinely, the new data have not been peer reviewed and insurance coverage may vary.
What did the PACE-A trial show?
At eight years, cancer control was similar after SBRT and surgery, while fewer SBRT patients needed daily urinary pads at five years.
What is SBRT?
Stereotactic body radiation therapy delivers high, precisely targeted doses of radiation in about five sessions over one to two weeks.
What should men ask their doctor?
Whether active surveillance is an option, whether they are candidates for SBRT or longer radiation, how their urinary health affects risk, and whether genetic testing would change the recommendation.
Published by Medicaldaily.com
