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Suspected clinically localised prostate cancer — MSRA MCQ

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HardPI-RADSSuspected clinically localised prostate cancerMSRA

A 69-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 6.2 micrograms/L and MRI-derived prostate volume is 62 mL (PSA density 0.10 ng/mL/mL). Digital rectal examination is benign and he has not previously had a prostate biopsy. Multiparametric MRI demonstrates a 14 mm focal lesion in the right posterolateral peripheral zone. It is markedly hypointense on the ADC map and markedly hyperintense on high-b-value diffusion-weighted imaging. T2-weighted imaging shows a circumscribed homogeneous hypointense lesion. Dynamic contrast-enhanced imaging shows no focal early enhancement. There is focal capsular breach with extension into the adjacent neurovascular bundle. Which PI-RADS v2.1 interpretation and immediate diagnostic management is most appropriate?

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

This is a peripheral-zone lesion, for which DWI is the dominant PI-RADS v2.1 sequence. Marked diffusion restriction would ordinarily give a DWI score of 4 when the lesion is under 15 mm. However, definite extraprostatic extension/invasive behaviour upgrades the lesion to DWI score 5 regardless of its 14 mm size. The overall PI-RADS category is therefore 5. Absence of focal early enhancement does not downgrade a peripheral-zone lesion that is already DWI 4 or 5; DCE chiefly resolves equivocal DWI score-3 peripheral-zone lesions. In UK practice, NICE recommends MRI-influenced biopsy for an MRI Likert score of 3 or more. A lesion with PI-RADS 5 morphology and extraprostatic extension would require urgent specialist diagnostic assessment with MRI-targeted/influenced biopsy. The low PSA density does not justify deferring biopsy because it is used principally to refine decisions after low-risk MRI findings (Likert 1–2), not to override a highly suspicious MRI lesion. A and C fail to account for extraprostatic extension, which makes the PI-RADS category 5 rather than 4. D incorrectly applies the PSA-density threshold to a high-risk MRI. E underestimates both the marked diffusion restriction and invasive behaviour.

Reference: NICE guideline NG131: Prostate cancer: diagnosis and management — MRI and biopsy recommendations (2019) — 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/