Study underway to assess 3-fraction SBRT regimen in prostate cancer

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Key Takeaways

The PRECISION study investigates a 3-fraction SBRT regimen for localized prostate cancer, aiming to reduce side effects compared to the 5-fraction regimen.
The study will enroll 100 patients, using the RayPilot Tumor Tracking System for real-time organ movement monitoring to improve treatment accuracy.
Primary outcomes include urinary and bowel toxicity, with secondary measures assessing IPSS, erectile, and bowel function scores.
Initial data from the study is anticipated in 1-2 years, with final results expected after 5 years of follow-up.

"The goal of the PRECISION study is to ensure that treatment with 3 radiation doses does not lead to greater side effects than those observed in the PACE-B study," says Professor Duncan B. McLaren, MBBS.

The first patients have been dosed in the phase 2 PRECISION study (NCT06117059), investigating the effectiveness of a 3-fraction regimen of stereotactic body radiotherapy (SBRT) in patients with low- to intermediate-risk localized prostate cancer, Micropos Medical announced in a news release.¹

The study was initiated in response to findings from the phase 3 PACE-B study (NCT01584258), which were published in 2024 in the New England Journal of Medicine.² Data showed that 5 fractions of SBRT was noninferior to conventionally or moderately hypofractioned SBRT in terms of biochemical or clinical failure in patients with low- to intermediate-risk localized prostate cancer.

Professor Duncan B. McLaren, MBBS

"The goal of the PRECISION study is to ensure that treatment with 3 radiation doses does not lead to greater side effects than those observed in the PACE-B study. I am confident that we can demonstrate effective cancer treatment with less side effects," said Professor Duncan B. McLaren, MBBS, of the Edinburgh Cancer Centre in Scotland, in the news release.¹

In total, the PRECISION study plans to enroll 100 patients with prostate cancer across clinical trial sites in the US and Europe. Patients will receive 3 fractions of SBRT over the course of 3 consecutive days. The RayPilot Tumor Tracking System will be used as a complement to treatment to enable real-time monitoring of organ movement. According to Micropos Medical, this tool can enable improved target accuracy, thereby minimizing potential adverse effects.

Patients included in the study must have low- to favorable intermediate-risk prostate cancer per National Comprehensive Cancer Center criteria, a prostate volume under 80cc, an International Prostate Symptom Score (IPSS) below 20, and a Qmax above 10cc per second and a urinary residual less than 150 mLs.³

Patients with previous TURP, hip replacements, or radiotherapy to the pelvis are not eligible for enrollment. Participants will also be excluded if they have T3a disease or above, a Gleason score of 7, or a PSA greater than 20 ng/mL.

The primary outcome measures include urinary and bowel toxicity, each measured using Radiation Oncology/Toxicity Grading (RTOG) and Common Terminology for Adverse Events criteria. Secondary outcome measures also include IPSS, erectile function scores, and bowel function scores.

According to Micropos Medical, initial data from the study are anticipated in 1 to 2 years. Final results will be reported following an additional 5 years of follow-up.

Data from PACE-B

PACE-B was a phase 3, open-label trial that enrolled 874 patients with localized prostate cancer. Patients were randomly assigned to receive a reduced dose of SBRT (n = 433; 36.25 Gy in 5 fractions over a period of 1 or 2 weeks) or conventionally or moderately hypofractioned SBRT (n = 441; 78 Gy in 39 fractions over a period of 7.5 weeks or 62 Gy in 20 fractions over a period of 4 weeks).

At a median follow-up of 74 months, the 5-fraction SBRT was shown to be noninferior to standard SBRT in the incidence of freedom from biochemical or clinical failure. Specifically, the 5-year incidence of freedom from biochemical or clinical failure was 95.8% (95% CI, 93.3 to 97.4) in the 5-fraction SBRT arm, compared with 94.6% (95% CI, 91.9 to 96.4) in the standard SBRT arm (unadjusted HR, 0.73; 90% CI, 0.48 to 1.12; P = .004 for noninferiority).

The cumulative incidence of RTOG grade 2 or greater genitourinary toxicity was 26.9% (95% CI, 22.8 to 31.5) in the 5-fraction SBRT arm vs 18.3% (95% CI, 14.8 to 22.5) in the standard SBRT arm (P < .001). Similarly, late RTOG grade 2 or higher gastrointestinal toxicity occurred in 10.7% (95% CI, 8.1 to 14.2) of patients in the 5-fraction arm vs 10.2% (95% CI, 7.7 to 13.5) of patients in the standard SBRT arm (P = .94).

REFERENCES

1. Micropos Medical: Precision study underway - 100 prostate cancer patients treated in just three radiation sessions. News release. Micropos Medical. March 27, 2025. Accessed April 14, 2025. https://micropos.se/2025/03/27/precision-study-underway-100-prostate-cancer-patients-treated-in-just-three-radiation-sessions/

2. van As N, Griffin C, Tree A, et al. Phase 3 trial of stereotactic body radiotherapy in localized prostate cancer. N Engl J Med. 2024;391(15):1413-1425. doi:10.1056/NEJMoa2403365

3. The PRECISION study: 3 fractions of prostate SBRT and RayPilot HypoCath Image Guidance (PRECISION). ClinicalTrials.gov. Last updated December 5, 2024. Accessed April 14, 2025. https://clinicaltrials.gov/study/NCT06117059