Adding endorectal magnetic resonance imaging (MRI) to the initial clinical evaluation of men with clinically low-risk prostate cancer helps to assess eligibility for active surveillance.

“Among patients initially diagnosed with clinically low-risk prostate cancer, those with tumors not clearly visualized on MRI were significantly more likely to demonstrate low-risk features when a confirmatory biopsy was performed, while patients with tumors clearly visualized on MRI were significantly more likely to have their disease status upgraded on confirmatory biopsy,” says lead investigator Hebert Alberto Vargas, MD, Department of Radiology, Memorial Sloan-Kettering Cancer Center. The study was published in Journal of Urology.

A total of 388 patients were evaluated, and these patients had an initial prostate biopsy performed between 1999 and 2010; had a Gleason score, which measures prostate cancer aggressiveness, of 6 or lower; and had a biopsy to confirm the assessment within 6 months of the initial diagnosis. All the patients had an endorectal MRI between the initial and confirmatory biopsies.

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The MRI studies were interpreted by three radiologists with different levels of experience. The first reader was fellowship trained and had previously read about 50 prostate MRI scans, the second reader was a fellow with dedicated training in prostate imaging who had read about 500 prostate MRI scans, and the third was a fellowship-trained radiologist who had read more than 5,000 prostate MRI scans. Each reader assigned a score of 1 to 5 for the presence of a tumor on the MRI, with 1 being definitely no tumor and 5 being definitely tumor.

After the confirmatory biopsies, Gleason scores were upgraded in 79 (20%) of the cases. Disease upgrades were more likely for the patients with higher MRI scores, while MRI scores of 2 or lower were highly associated with low-risk features on confirmatory biopsy. The second and third readers had substantial agreement on MRI scores, but only fair agreement was reached between the first reader and the second or third reader.

“These results suggest that MRI of the prostate, if read by radiologists with appropriate training and experience, could help determine active surveillance eligibility and obviate the need for confirmatory biopsy in substantial numbers of patients,” notes Dr. Vargas.

Active surveillance allows patients who have low-grade tumors to avoid negative side effects of prostate cancer treatment, but its success relies primarily on accurately identifying those patients who have low-risk disease that is unlikely to progress. “The fact that clear tumor visualization on MRI was predictive of upgrading on confirmatory prostate biopsy suggests that prostate MRI may contribute to the complex process of assessing patient eligibility for active surveillance,” Dr. Vargas concludes.