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Suspected clinically localised prostate cancer — MSRA MCQ

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HardPI-RADSSuspected clinically localised prostate cancerMSRA

A 62-year-old man is investigated on the suspected prostate cancer pathway. He would be suitable for radical treatment if clinically significant prostate cancer were diagnosed. His PSA is 4.8 micrograms/L, MRI-derived prostate volume is 64 mL (PSA density 0.075 ng/mL/mL), digital rectal examination is benign, and there is no family history of prostate cancer. Multiparametric MRI identifies a 17 mm discrete lesion in the left posterolateral peripheral zone. It is markedly hypointense on the ADC map and markedly hyperintense on high-b-value diffusion-weighted imaging. On T2-weighted imaging it is a circumscribed, moderately hypointense focus. Dynamic contrast-enhanced imaging shows no focal early enhancement, and there is no extracapsular extension. Which PI-RADS v2.1 interpretation and immediate diagnostic management is most appropriate?

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Correct answer: E — PI-RADS 5; offer MRI-influenced prostate biopsy

Explanation lettering: D = shown as C · E = shown as D · C = shown as E

This is a PI-RADS 5 peripheral-zone lesion requiring MRI-influenced prostate biopsy. In the peripheral zone, DWI is the dominant sequence. A discrete lesion with both marked ADC hypointensity and marked high-b-value DWI hyperintensity is DWI score 4 when smaller than 1.5 cm, but score 5 when it measures more than 1.5 cm in greatest dimension. At 17 mm, this lesion therefore meets the size criterion for PI-RADS 5. Extracapsular extension is not required for category 5. The absence of focal early enhancement does not reduce the category: DCE is principally used to upgrade an otherwise equivocal peripheral-zone DWI score 3 lesion to PI-RADS 4. It does not downgrade a lesion that is already DWI score 5. A low PSA density and benign examination reduce pre-test probability but do not override a highly suspicious MRI lesion. In UK practice, NICE recommends MRI-influenced biopsy for MRI Likert scores of 3 or more; a PI-RADS 5 lesion would be expected to be managed as a high-suspicion MRI finding. A and E incorrectly under-score the marked diffusion restriction and lesion size. B is plausible because marked restricted diffusion commonly indicates PI-RADS 4, but misses the greater-than-1.5-cm upgrade. D inappropriately applies the PSA-density safety-net used for low-risk MRI findings.

Reference: NICE NG131: Prostate cancer: diagnosis and management — Assessment and diagnosis, MRI and biopsy (2019; checked 16 August 2026) — https://www.nice.org.uk/guidance/ng131/chapter/Recommendations PI-RADS v2.1: What has changed and how to report (2021) — https://pubmed.ncbi.nlm.nih.gov/34230862/ Prostate imaging reporting and data system version 2 (PI-RADS v2): a pictorial review (2016) — https://pubmed.ncbi.nlm.nih.gov/27522352/