MRI-Guided SBRT Cuts Long-Term Toxicities in Prostate Cancer

TOPLINE:

Aggressive margin reduction with MRI-guided stereotactic body radiotherapy (SBRT) led to a significantly lower incidence of late genitourinary and gastrointestinal toxicities at 2 years compared with CT-guided SBRT in men with localized prostate cancer, new data showed.

METHODOLOGY:

• MRI-guided SBRT is known to reduce planning margins in prostate cancer and lead to less acute toxicity compared with standard CT-guided SBRT. However, the long-term benefits of the MRI-guided approach remain unclear.
• To find out, researchers conducted the phase 3 MIRAGE trial, in which 156 patients with localized prostate cancer were randomly assigned to receive either MRI-guided SBRT with 2-mm margins or CT-guided SBRT with 4-mm margins.
• The MIRAGE trial initially reported the primary outcome of acute genitourinary grade ≥ 2 toxicity within 90 days of SBRT.
• In this secondary analysis, researchers evaluated physician-reported late genitourinary and gastrointestinal toxicity, along with changes in various patient-reported quality-of-life scores over a 2-year follow-up period.

TAKEAWAY:

• Over a period of 2 years, MRI-guided SBRT was associated with a significantly lower cumulative incidence of grade ≥ 2 genitourinary toxicities compared with CT-guided SBRT (27% vs 51%; P = .004). Similar outcomes were noted for grade ≥ 2 gastrointestinal toxicities (1.4% with MRI vs 9.5% with CT; P = .025).
• Fewer patients who received MRI-guided SBRT reported deterioration in urinary irritation between 6 and 24 months after radiotherapy — 14 of 73 patients (19.2%) in the MRI group vs 24 of 68 patients (35.3%) in the CT group (P = .031).
• Patients receiving MRI-guided SBRT were also less likely to experience clinically relevant deterioration in bowel function (odds ratio [OR], 0.444; P = .035) and sexual health score (OR, 0.366; P = .03).
• Between 6 and 24 months after radiotherapy, 26.4% of patients (19 of 72) in the MRI group vs 42.3% (30 of 71) in the CT group reported clinically relevant deterioration in bowel function.

IN PRACTICE:

“Our secondary analysis of a randomized trial revealed that aggressive planning for margin reduction with MRI guidance vs CT guidance for prostate SBRT led to lower physician-scored genitourinary and gastrointestinal toxicity and better bowel and sexual quality-of-life metrics over 2 years of follow-up,” the authors wrote.

SOURCE:

This study, led by Amar U. Kishan, University of California Los Angeles, was published online in European Urology.

LIMITATIONS:

The absence of blinding in this study may have influenced both physician-scored toxicity assessments and patient-reported quality-of-life outcomes. Additionally, the MIRAGE trial was not specifically designed with sufficient statistical power to evaluate the secondary analyses presented in this study.

DISCLOSURES:

This study was supported by grants from the US Department of Defense. Several authors reported receiving grants or personal fees and having other ties with various sources.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.