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Suspected clinically localised prostate cancer in a man taking finasteride — MSRA MCQ

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HardPSASuspected clinically localised prostate cancer in a man taking finasterideMSRA

A 65-year-old man is reviewed in urology after referral for nocturia and reduced urinary flow. He has taken finasteride 5 mg daily for 14 months with good adherence. Before starting finasteride, his PSA was 5.0 micrograms/L. His PSA fell to 2.4 micrograms/L after 6 months but is now 3.1 micrograms/L, measured using the same assay. He has no urinary infection, retention, recent catheterisation or instrumentation, and avoided ejaculation and vigorous cycling for 48 hours before testing. Digital rectal examination is benign. Multiparametric MRI shows a Likert score of 2 and a prostate volume of 36 mL. He is fit for radical treatment should clinically significant prostate cancer be identified and wishes to continue investigation. What is the most appropriate next management step?

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Correct answer: C — Offer a systematic prostate biopsy

Explanation lettering: C = shown as A · D = shown as B · A = shown as C · B = shown as D

Finasteride reduces PSA by approximately 50% after 6 months or more; therefore this PSA of 3.1 micrograms/L should be interpreted as approximately 6.2 micrograms/L in an untreated man. His adjusted PSA density is therefore about 0.17 ng/mL/mL (6.2/36), exceeding the NICE example threshold of 0.15 for strong suspicion of prostate cancer. The sustained PSA rise from the finasteride-associated nadir further supports concern. Although a Likert 1 or 2 MRI permits biopsy omission in some people, NICE recommends offering biopsy where suspicion remains strong, including PSA density above 0.15, after considering fitness and preferences. As there is no MRI lesion to target, the appropriate biopsy is systematic (typically performed by a local transperineal or transrectal pathway). B and C would be appropriate where MRI is low risk and PSA density/kinetics indicate low suspicion. D is unsuitable because MRI-targeted biopsy is indicated for Likert 3 or greater lesions. E is not appropriate for initial assessment outside a clinical trial.

Reference: NICE NG131: Prostate cancer: diagnosis and management — MRI and biopsy; if the MRI or biopsy is negative (2019; current NICE page checked August 2026) — https://www.nice.org.uk/guidance/ng131/chapter/Recommendations Finasteride 5 mg film-coated tablets — Summary of Product Characteristics (Updated 2025) — https://www.medicines.org.uk/emc/product/13543/smpc