MRI Guidance for Stereotactic Body Radiotherapy Reduced Toxic Effects Among Patients With Prostate Cancer

Results from the Phase 3 MIRAGE Trial

A significant reduction of moderate acute physician-scored toxic effects and decrements in patient-reported quality of life was noted with magnetic resonance imaging (MRI)-guided stereotactic body radiotherapy (SBRT) vs computed tomography (CT)-guided, for patients with clinically localized prostate adenocarcinoma.

Amar Kishan, MD, University of California, Los Angeles, California, and coauthors wrote, “Both acute and late toxic effects can manifest as urinary, bowel, and sexual dysfunction and contribute to treatment-related burden [with CT-guided SBRT].” While MRI-guided SBRT has become commercially available and offers multiple theoretical advantages, “these advantages have yet to be demonstrated in a randomized clinical trial.” The MIRAGE trial aimed “to demonstrate that aggressive [planning target volume] margin reduction with MRI-guided radiotherapy reduces acute toxic effects following SBRT for localized prostate cancer.”

In this nonblinded, single-center, phase 3 clinical trial, 156 patients with clinically localized prostate cancer who were receiving SBRT were enrolled between May 5, 2020, and October 1, 2021. Patients were randomized on a 1-to-1 basis to receive either SBRT with CT guidance (control arm, n = 77) or SBRT with MRI guidance (MRI arm, n = 79). The primary end point of the study was the incidence of acute grade ≥2 genitourinary toxic effects within 90 days following SBRT.

At the data cut-off date of May 15, 2022, all patients had a follow-up duration of ≥3 months. The incidence of acute grade ≥2 genitourinary toxic effects was 24.4% in the MRI arm and 42.4% in the control arm, representing a statistically significant difference (P = .01). The incidence of acute grade ≥2 gastrointestinal toxic effects was also significantly lower in the MRI arm vs the CT arm (0.0% vs 10.5%; P = .003). There was an association between MRI guidance and a lower percentage of patients with a ≥15-point increase in International Prostate Symptom Score at 1 month (6.8% vs 19.4%; P = .01) and ≥12-point decrease in Expanded Prostate Cancer Index Composite-26 bowel scores at 1 month (25.0% vs 50.0%; P = .001).

Limitations to the study included: a lack of blinding, single-center setting, and debatable clinical significance of acute toxicity end points.

Dr Kishan et al concluded, “our results demonstrated that the aggressive margin reduction afforded by MRI guidance allowed a substantial reduction in acute physician-scored toxic effects as well as multiple patient-reported outcomes metrics.” They added that longer-term follow-up is needed to determine whether these improvements will apply to late toxic effects and differences in sexual outcomes will occur.

Source:

Kishan AU, Ma TM, Lamb JM, et al. Magnetic Resonance Imaging-Guided vs Computed Tomography-Guided Stereotactic Body Radiotherapy for Prostate Cancer. JAMA Oncol. Published online January 12, 2023. doi:10.1001/jamaoncol.2022.6558