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Multiparametric MRI Is Often False-Negative for Clinically Significant Prostate Cancer

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Originally published on Urologic Oncology: Seminars and Original Investigations

Key findings

  • This study compared 301 patients who had suspicious results on prostate multiparametric MRI (mpMRI) and had prostate cancer detected during subsequent biopsy with 215 patients who did not have suspicious mpMRI
  • Clinically significant prostate cancer was detected in 15% of the nonsuspicious group
  • The nonsuspicious group had significantly lower median tumor volume than the suspicious group (40% vs. 50%, P=0.005), but the 40% figure indicates many relatively large tumors went undetected by mpMRI
  • Prostate-specific antigen density >0.15 ng/mL/cc was a statistically significant independent predictor of clinically significant prostate cancer in the nonsuspicious group
  • 20-core standard template biopsy should not be routinely omitted for patients who have negative prostate mpMRI

Multiparametric magnetic resonance imaging (mpMRI) has substantially improved the detection and localization of prostate cancer. However, there's still no consensus about how to manage patients who have a negative mpMRI but persistent clinical suspicion of prostate cancer.

Chin-Lee Wu, MD, PhD, director of Genitourinary Pathology Services at Massachusetts General Hospital, Douglas M. Dahl, MD, vice-chair in the Department of Urology and chief of the Division of Urologic Oncology, and colleagues recently completed a retrospective study to address this question.

Their report in Urologic Oncology: Seminars and Original Investigations suggests false-negative rates of mpMRI for clinically significant prostate cancer are substantial, reaching 15%, and confirmatory biopsy may often be advisable.

Methods

From a transperineal biopsy database, the team identified 516 patients who underwent prostate mpMRI and subsequent biopsy between September 2019 and February 2021:

  • Suspicious group—301 patients who had one or more suspicious lesions on mpMRI and underwent both transperineal standard template biopsy (20-core) and targeted biopsy
  • Nonsuspicious group—215 patients who had negative mpMRI and underwent only transperineal standard template biopsy

Negative mpMRI was defined as the absence of suspicious findings and/or the presence of low-risk areas with a Prostate Imaging Reporting and Data System (PI-RADS) score ≤2.

Detection of Prostate Cancer

Standard template biopsy detected:

  • Any prostate cancer, the primary endpoint, in 74% of the suspicious group and 43% of the nonsuspicious group (P<0.001)
  • Clinically significant prostate cancer in 39% of the suspicious group and 15% of the nonsuspicious group (P<0.001)

Negative Predictive Values (NPV)

The NPV of mpMRI for any prostate cancer was:

  • 74% across all patients
  • 69% in patients with elevated prostate-specific antigen (PSA) or abnormal digital rectal examination
  • 87% in patients under active surveillance because of a prior diagnosis of prostate cancer

The NPV of mpMRI for clinically significant prostate cancer was:

  • 85% across all patients
  • 84% in patients with elevated PSA or abnormal digital rectal examination
  • 87% in patients under active surveillance

Tumor Volume

In the nonsuspicious group, the greatest percentage of cancer involvement (GPC) of biopsy cores was significantly lower than that in the suspicious group (median 40% vs. 50%; P=0.005). Thus, mpMRI can be negative even when the tumor volume is large.

Predictor of Prostate Cancer

In multivariate analysis, only PSA density >0.15 ng/mL/cc was a statistically significant independent predictor of clinically significant prostate cancer in the nonsuspicious group.

Guidance for the Clinic

20-core standard template biopsy should not be routinely omitted for patients who have negative prostate mpMRI. For patients with nonsuspicious imaging and higher PSA density, a confirmatory biopsy is especially important due to the increased risk that mpMRI will miss clinically significant prostate cancer.

15%
of patients who had nonsuspicious multiparametric MRI scans were diagnosed by biopsy as having clinically significant prostate cancer

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