Stereotactic body radiotherapy (SBRT) is a standard treatment for localized prostate cancer. However, the side effects of this treatment can be severe and long-lasting, impacting a patient’s urinary, bowel, and sexual functions. To protect healthy tissue, imaging scans are used to plan radiation therapy, creating small margins around the tumor. Magnetic resonance imaging (MRI) guidance allows for more precise treatment, reducing the margins around the prostate, which means less exposure to surrounding healthy tissue. The primary goal in radiation oncology research is to optimize radiation delivery to the tumor while minimizing damage to surrounding structures. Previous studies have indicated that MRI guidance for aggressive margin-reduction (AMR) in SBRT for prostate cancer reduces acute toxicity, but the long-term benefits remained unclear. A two-year analysis has now confirmed that MRI-guided SBRT not only reduces acute treatment toxicity but also offers sustained benefits for patients' quality of life.

In a two-year follow-up study, researchers from the UCLA Health Jonsson Comprehensive Cancer Center (Los Angeles, CA, USA) discovered that MRI-guided SBRT significantly reduced long-term side effects and enhanced quality of life, particularly in terms of bowel and sexual health, compared to traditional CT-guided treatment. This study was a secondary analysis of the phase 3 MIRAGE clinical trial, which assessed the impact of MRI guidance in delivering high-precision radiation therapy for prostate cancer, as opposed to the standard CT-guided SBRT that requires larger treatment margins.

The results revealed that patients receiving MRI-guided SBRT experienced fewer urinary and bowel side effects. Specifically, 27% of MRI-guided patients reported moderate or severe urinary issues, such as incontinence and irritation, compared to 51% of those receiving CT guidance. Furthermore, gastrointestinal toxicity, including bowel problems, was observed in only 1.4% of MRI-guided patients, a significant reduction compared to 9.5% in the CT-guided group. MRI guidance also led to improved scores on quality-of-life assessments, particularly in bowel function and sexual health. These findings, published in European Urology, suggest a promising shift in prostate cancer treatment, highlighting the potential of MRI-guided radiation therapy to improve patient outcomes.

“This study adds strong evidence that the enhanced precision and accuracy afforded by MRI-guided SBRT leads to significantly fewer urinary, bowel, and sexual side effects for men receiving prostate SBRT,” noted Dr. Amar Kishan, executive vice chair of radiation oncology at the David Geffen School of Medicine at UCLA and first author of the study. “The MRI-guided approach, which includes real-time tracking of the prostate itself and the use of a built-in MRI to help deliver the radiation, allows us to use significantly narrower planning margins when delivering radiation, leading to less radiation to normal tissues. This in turn reduces the risk of enduring side effects that can impact a patient’s quality of life." 

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