MRI-Based Model for Prostate Biopsy Risk Stratification

Key Points

  • The MRI-based model improved predictive area under the curve to 84% from 64% with the clinical model.
  • The MRI-based model would have resulted in 18 fewer biopsies per 100 men.

In a study reported in JAMA Oncology, Mehralivand et al found that inclusion of magnetic resonance imaging (MRI) findings in a predictive model may reduce unnecessary biopsies in men with suspected prostate cancer.

Study Details

In the study, a predictive model adding MRI-derived prostate volume and Prostate Imaging-Reporting and Data System version 2 (PI-RADSv2) category (with category ≤ 2 as reference) to clinical variables (age, African American ethnicity, prior negative biopsy, abnormal results of digital rectal exam, and prostate-specific antigen level) was developed in a cohort of 400 patients from a single institution. The model was tested in a validation cohort of 251 patients from 2 independent institutions. Patients underwent MRI, MRI/transrectal ultrasound (TRUS) fusion–guided biopsy, and 12-core systematic biopsy in one session.

The primary outcome was the risk of clinically significant prostate cancer on biopsy, defined as a Gleason score of 3 + 4 or higher in at least one biopsy core.

Predictive Ability

Overall, 193 of 400 patients (48.3%) in the development cohort and 96 of 251 patients (38.2%) in the validation cohort had clinically significant prostate cancer. Use of the MRI-based predictive model in the validation cohort improved the receiver operating characteristic area under the curve to 84% compared with 64% with the baseline clinical model (P < .001). At a risk threshold of 20%, the MRI model had a much lower rate of false-positives vs the baseline model (46% vs 92%) and a small reduction in the true-positive rate (89% vs 99%). The net reduction in the number of false-positive findings with the MRI-based model vs having to perform a biopsy in all patients with positive MRI results was equivalent to 18 fewer unnecessary biopsies per 100 men, with no increase in the number of missed clinically significant prostate cancers.

The investigators concluded: “The inclusion of MRI-derived parameters in a risk model could reduce the number of unnecessary biopsies, while maintaining a high rate of diagnosis of clinically significant prostate cancers.”

The study was funded by the National Cancer Institute.

Baris Turkbey, MD, of the Molecular Imaging Program, National Cancer Institute, is the corresponding author of the JAMA Oncology article.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.


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