Prebiopsy IMPROD Biparametric Magnetic Resonance Imaging Combined with Prostate-Specific Antigen Density in the Diagnosis of Prostate Cancer: An External Validation Study

Background: Biparametric magnetic resonance imaging (bpMRI) combined with prostate-specific antigen density (PSAd) may be an effective strategy for selecting men for prostate biopsy. It has been shown that performing biopsy only for men with bpMRI Likert scores of 4-5 or PSAd ≥0.15 ng/ml/cm³ is the most efficient strategy.

Objective: To externally validate previously published biopsy strategies using two prospective bpMRI trial cohorts.

Design, setting, and participants: After IMPROD bpMRI, 499 men had systematic transrectal prostate biopsies and men with IMPROD bpMRI Likert scores of 3-5 had an additional two to four targeted biopsies.

Outcome measurements and statistical analysis: Various IMPROD bpMRI Likert score and PSAd thresholds were assessed using detection rates for significant prostate cancer (sPCa; Gleason score ≥3 + 4), predictive values, and proportion of biopsies avoided. Net benefits and decision curve analyses (DCA) were compared with the aim of finding an optimal strategy for sPCa detection. Combined biopsies were used for reference.

Results and limitations: The negative predictive value (NPV) for sPCa in IMPROD bpMRI Likert 3-5 and 4-5 score groups was 93% and 92%, respectively, while the corresponding positive predictive value (PPV) was 57% and 72%, respectively. In DCA, the optimal combination was IMPROD bpMRI Likert score 4-5 or Likert 3 with PSAd ≥0.20 ng/ml/cm³, which had NPV of 93% and PPV of 67%. Using this combination, 35% of the study patients would have avoided biopsies and 13 sPCas (6%, 13/229, of all sPCas diagnosed) would have been missed.

Conclusions: IMPROD bpMRI demonstrated a good NPV for sPCa. PSAd improved the NPV mainly among men with equivocal suspicion on IMPROD bpMRI. However, the additional value of PSAd was marginal: the NPV and PPV for IMPROD bpMRI Likert 4-5 score group were 92% and 72%, respectively, while the corresponding values for the best combination strategy were 93% and 67%.

Patient summary: We investigated a rapid prostate magnetic resonance imaging protocol (IMPROD bpMRI) combined with prostate-specific antigen (PSA) density for detection of significant prostate cancer. Our results show that IMPROD bpMRI is a good diagnostic tool, but the additional value provided by PSA density is marginal.