The PROSTOX ultra genetic test is now commercially available in the US for use in predicting which patients with localized prostate cancer are at higher risk of developing late genitourinary (GU) toxicity from stereotactic body radiotherapy (SBRT), MiraDx announced in a news release.1

Patients with a high PROSTOX score do not appear to be at higher risk for toxicity with other radiation regimens.

The test was previously available through an Early Access Program at select academic centers and private practices.

“Initial data from the PROSTOX Early Access Program in patients identified as having a high risk of toxicity to SBRT found that results from the test changed the course of treatment for 77% of these patients, helping them avoid potential complications from SBRT,” said Melissa Stoppler, MD, executive vice president of medical affairs at MiraDx, in the news release from the company.1 “Extending access to this test to a broader range of clinicians and clinical settings will enable more prostate cancer patients to benefit from testing for these novel biomarkers of toxicity to radiation treatments.”

MiraDx is also offering a financial assistance program that will provide reduced pricing to PROSTOX ultra based on household income.

Data on PROSTOX ultra

The commercial launch of PROSTOX ultra comes soon after data on the genetic test were presented at the American Society for Radiation Oncology (ASTRO)’s 67th Annual Meeting in San Francisco, California.2,3

Overall, the study showed that patients identified as genetically high-risk for GU toxicity after SBRT most frequently choose a different form of radiation and that they do not appear to be at higher risk of toxicity with these other radiation regimens. In total, the study included 98 patients with prostate cancer and PROSTOX ultra results indicating a high risk of GU toxicity from SBRT.

Among all patients in the study, 26.5% proceeded with SBRT, 46.9% received either moderately hypofractionated radiotherapy (MHFRT) or conventionally fractionated radiotherapy (CFRT), 18.4% underwent a radical prostatectomy, and 8% received high-dose rate (HDR) brachytherapy or other treatments (focal ultrasound ablation or cryotherapy).

At a minimum follow-up of 12 months, 36.8% of patients received radiotherapy experienced late grade >2 GU toxicity. However, data showed substantial differences in the rate of late grade >2 GU toxicity across radiation treatment groups. Specifically, the rate was 7.1% (95% CI, 1.5 to 19.5) among those who underwent MHFRT or CFRT, compared with 83.3% (95% CI, 62.6 to 95.3) among those who proceeded with SBRT.

According to the authors, “These differences were statistically different between MHFRT/CFRT and SBRT (Fisher’s exact p=3.6 x 10-10).”

“We were excited to confirm both that high-risk results from PROSTOX ultra testing encouraged patients and their doctors to choose alternative treatment courses for their prostate cancer. And, importantly, that these alternative approaches tended to be safe for them,” said Joanne Weidhaas, MD, professor at the David Geffen School of Medicine and head of translational research in the department of radiation oncology at UCLA, in a news release.3 “These are important steps towards truly personalizing radiation therapy—identifying the small subsets of patients who are inherently radiosensitive to one radiation regimen versus another, to enable choice.”

REFERENCES

1. MiraDx announces the commercial availability of PROSTOX™ ultra for prediction of risk of late genitourinary toxicity in prostate cancer patients considering radiation therapy. News release. MiraDx. October 2, 2025. Accessed October 7, 2025. https://miradx.com/prostox-commerically-available/

2. Kishan AU, McGreevy K, Telesca D, Weidhaas JB. Treatment choices and toxicity outcomes in patients with a high risk PROSTOX score. Presented at: American Society for Radiation Oncology 67th Annual Meeting. September 27-October 1, 2025. San Francisco, California. Poster 3362

3. MiraDx announces new research conducted by UCLA and other academic centers presented at ASTRO 2025 that confirms that prostate cancer patients identified as high-risk with PROSTOX™ ultra for SBRT toxicity can safely receive other radiation regimens. News release. MiraDx. September 29, 2025. Accessed October 7, 2025. https://miradx.com/high-risk-sbrt-toxicity-can-safely-receive-other-radiation-regimens/