Should MRI be Mandatory Prior to Active Surveillance Decisions for Patients with Intermediate Risk Prostate Cancer?

New research suggests the use of prostate magnetic resonance imaging (MRI) may have a considerable impact on the management of patients deemed to have low-risk and intermediate-risk prostate cancer (PCa).

For the retrospective study, recently published in the Journal of Urology, researchers reviewed MRI data from 1,204 men with newly diagnosed low-risk PCa and 287 men with favorable intermediate-risk PCa as per classification guidelines from the National Comprehensive Cancer Network (NCCN). The patients in the cohort (median age of 64) were drawn from the 46-facility Michigan Urological Surgery Improvement Collaborative registry and all had active surveillance from June 2016 to January 2021, according to the study. The researchers noted a median follow-up of 11 months.

The researchers found that PI-RADS > 4 was associated with a 17.4 percent cumulative incidence of biopsy reclassification at two years in comparison to 8.5 percent for patients with PI-RADS 1-3 lesions. At 48 months, the cumulative incidence for biopsy reclassification was 43.1 percent in patients with PI-RADS > 4 lesions in contrast to 32.4 percent for those with PI-RADS 1-3 lesions, according to the study authors.

Multivariable analysis revealed that biopsy reclassification was 2.3 times more likely with PI-RADS > 4 assessments than PI-RADS 1-3 prostate lesions.

“ … We found that higher baseline MRI PI-RADS (score 4/5) was independently associated with higher hazard of biopsy reclassification to > GG3 disease, adjusted for clinical and pathologic factors,” wrote lead study author Kiran R. Nandalur, M.D., who is affiliated with the Department of Radiology and Molecular Imaging at the William Beaumont University Hospital in Royal Oak, Mich., and colleagues.

(Editor’s note: For additional content on prostate cancer imaging, click here.)

The researchers also noted significant percentages of high PI-RADS scoring among patients in grade group 1 (GG1) or those deemed to have low risk of PCa as per NCCN classification. Over 86 percent of patients with PI-RADS > 4 lesions were in grade group 1 and over 79 percent were in the low NCCN risk group, according to the study authors.

“Given the favorable outcomes in these patients based on current models, the prognostic role of MRI appears to be largely adjunctive to potentially aid in identifying the small number of patients at increased hazard of reclassification and identifying patients who may be very low hazard and need less intense follow-up,” posited Nandalur and colleagues.

In addition to finding no statistically significant correlations between MRI PI-RAD assessments and GG or NCCN classifications, the researchers noted no difference between PI-RADS 3 assessments and PI-RADS 1 and 2 interpretations with respect to biopsy reclassifications.

“In our study, patients with baseline PI-RADS 3 lesions were not at significantly higher hazard of reclassification than those with low PI-RADS (1/2), suggesting these patients can be counseled similar to low suspicion MRI findings and managed with less intensive follow-up,” added Nandalur and colleagues.

(Editor’s note: For related content, see “Study: mpMRI-Targeted Biopsies Offer Better Detection of Cribriform and Intraductal PCa than Systematic Biopsies,” “Study: PSMA PET/CT More Advantageous than MRI for Locoregional Staging of Prostate Cancer” and “Could MRI-Based AI Offer Better Risk Stratification for Prostate Cancer than PI-RADS?”)

In regard to study limitations, the authors acknowledged variable follow-up timing and a lack of clarity on whether PI-RADS version 2 or version 2.1 was utilized in initial MRI assessment in the cohort. The researchers also noted a lack of clarity on whether MRI and biopsy results correlated to the same areas.