A study led by researchers at the UCLA Jonsson Comprehensive Cancer Center has found that magnetic resonance imaging, or MRI, frequently underestimates the size of prostate tumors, potentially leading to undertreatment.
January 11, 2021 — A study led by researchers at the UCLA Jonsson Comprehensive Cancer Center has found that magnetic resonance imaging, or MRI, frequently underestimates the size of prostate tumors, potentially leading to undertreatment.
The study authors found that such underestimation occurs most often when the MRI-measured tumor size is small and the PI-RADS score, which is used to classify lesions in prostate MRI analysis, is low.
For prostate tumor treatments to be successful, both the MRI size measurement and PI-RADS score must be accurate because they allow physicians to determine precisely where tumors end and where the normal, healthy tissue surrounding them begins.
MRI is frequently used to diagnose and manage prostate cancer. It is also increasingly used as a means to map and guide delivery of new, highly focused therapies that use freezing (cryotherapy), ultrasound (HIFU) and heat (laser ablation) to destroy cancerous tissue in the prostate gland while sparing healthy tissue.
Researchers compared MRI-measured tumor size with actual tumor size after prostate removal in 441 men treated for prostate cancer.
Improving the ability to better predict ablation margins will allow for more successful treatments for men with prostate cancer and can help reduce the morbidity of prostate cancer treatment.
For more information: www.uclahealth.org
September 28, 2026 
