MRI-Guided Radiotherapy Improves Prostate Cancer Outcomes, Comparison

January 18, 2023 - For patients with prostate cancer, magnetic resonance imaging (MRI)-guided radiotherapy led to better outcomes than computed tomography (CT)-guided radiotherapy. This clinical trial supported claims that MRI-guided radiotherapy improved margin reductions for patients with prostate cancer, thus improving patient outcomes and quality of life.

Researchers in the publication noted, “compared with CT guidance, MRI-guided SBRT significantly reduced both moderate acute physician-scored toxic effects and decrements in patient-reported quality of life. Longer-term follow-up will confirm whether these notable benefits persist.”

The study was a phase III randomized clinical trial that recruited 156 patients with prostate cancer. All participants were 18 or older when they were recruited between May 5, 2020, and October 1, 2021. Patients underwent stereotactic body radiotherapy (SBRT) for a clinically localized prostate adenocarcinoma. Data were analyzed between January 15, 2021, and May 15, 2022, with each patient undergoing three or more months of follow-ups.

All patients received 40 Gy of SBRT in five sessions, with half guided by CT (4 mm margins) and the other half directed by MRI (2 mm margins). According to the research, MRI-guided SBRT had a significantly lower incidence of genitourinary toxic effects, at 24.4% compared to 43.4%.

Gastrointestinal side effects and toxicities were virtually nonexistent for those treated with MRI-guided SBRT, with an incidence of 0%. Conversely, those undergoing CT-guided SBRT had a 10.5% incidence of gastrointestinal toxicities.

Additionally, MRI-guided therapy was less likely to cause a 15 or greater point increase in the  International Prostate Symptom Score (IPSS). Only 6.8% of MRI-guided patients had a significant rise in IPSS compared to 19.4% in the CT-guided group. Finally, researchers stated that only one-quarter of patients in the MRI-guided therapy group had elevated Expanded Prostate Cancer Index Composite-26 (EPIC-26) bowel scores. In contrast, half of those in the CT-guided group did.

"We felt that MRI-guided radiotherapy allows a much tighter margin around the prostate to be targeted due to the enhanced imaging capabilities of MRI and the ability to track the prostate and control the beam in real-time during treatment. The significant reduction in urinary and bowel toxicity seen in our trial reflects the importance and relevance of this tighter margin made possible by MRI-guided radiation therapy,” said Amar Kishan, MD, Chief of the Genitourinary Oncology Service at UCLA, in a press release.