Caution with finasteride and over-the-counter supplements when interpreting PSA results

Mr Editor

We note with interest the points made in this article and the evolving discussion of the pros and cons of a national prostate cancer screening program in the UK. Prostate Cancer UK has recently highlighted advances in the diagnostic utility of mpMRI, which may change the risk/benefit ratio in favor of a national screening programme. The UK National Screening Committee has confirmed that it will look into the possibility of a screening program for all men over 50, as well as men over 45 who are black, or men who have a first degree relative with prostate, breast or ovarian cancer – the highest risk groups (Ref 1).

Due to increased awareness and media discussion, an increasing number of asymptomatic men are presenting to primary care for routine PSA testing – so counseling around a PSA blood test is clearly very important.

The NICE Clinical Knowledge Summary (CKS – Ref 2) advises against checking a PSA in men who have an active UTI or UTI within the previous 6 weeks, who have ejaculated, or exercised vigorously (eg, riding a bicycle) in the previous 48 hours, or who had a urological procedure such as a prostate biopsy in the previous 6 weeks. However, there is no mention in the CKS guidelines, or on the NHS website (Ref 3), of the potential effect of ‘over the counter’ drugs and supplements on PSA results.

Finasteride is a commonly prescribed drug to shrink an enlarged prostate and will usually halve the PSA within 9 to 12 months. The PSA will then remain at this “halved” level for the duration of finasteride. Hopefully GPs and those interpreting a PSA result will be aware of this, but perhaps only when the patient has an active prescription on their medical notes. But what about patients who buy finasteride through online pharmacies for hair loss? Unless specifically requested (or unless the patient voluntarily gives the information or has been counseled about it at the point of sale), this could be a blind spot for the PSA interpreter and the patient.

Saw Palmetto is a commonly taken supplement from the fruit of the Serenoa repens tree (a dwarf palm with saw-like leaves native to the southeastern United States). It is claimed to help with an enlarged prostate, improve urinary function and improve hair growth. Some claim the supplement can boost libido and fertility, reduce inflammation, and have anti-cancer effects. It can also theoretically reduce PSA (Ref 4).

With the margins for the need for further investigation being so slim, we urge that anyone advising on PSA blood testing be aware of the potential for a suppressed PSA due to medications or supplements and hope that this information becomes more commonplace. on patient information. data sheets, national guidelines and websites.

Dr Simon Hodes – General Practitioner, Mountwood Surgery Northwood and Cleveland Clinic London.

Prof Prasanna Sooriakumaran – Professor of Urology, Cleveland Clinic Lerner College of Medicine; Visiting Professor of Urology, University of Oxford; Consultant Urological Surgeon, Cleveland Clinic London & University College London Hospitals.

Ref 1 – https://prostatecanceruk.org/about-us/news-and-views/2023/02/our-new-res…

Ref 2 – https://cks.nice.org.uk/topics/prostate-cancer/diagnosis/assessment/#inf…

Ref 3 – https://www.nhs.uk/conditions/prostate-cancer/psa-testing/

Ref 4 – https://www.aafp.org/pubs/afp/issues/2003/0315/p1281.html