Is it time to put a CAP on the number of PSA screening tests we are doing?

Is it time to put a CAP on the number of PSA screening tests we are doing?
'All screening programmes do harm; some do good as well, and, of these, some do more good than harm at reasonable cost’. This was the opening salvo in a review article written in the BMJ 10 years ago in 2008, entitled ‘Maximising the benefit and minimising the harm of screening’. It was prompted by the pledge of the Labour Government to increase screening services in the UK, and used the lessons of the breast cancer screening programme to offer advice on how to make screening programmes as effective as possible.

Whilst the review was specifically on screening programmes, I think that initial comment should remain in the back of our mind when considering individual screening tests, with PSA screening one good example. Screening is a seductive concept for patients, clinicians and politicians alike - catch it early, treat it early, get a better outcome. It all sounds so simple. But as we know, it is not as straightforward as that, and discussing the nuances of the pros and cons of screening with individuals is difficult, especially when they are encouraged to ‘get checked’ by well-meaning friends, family and celebrities. 

The latest piece of evidence to help inform the PSA screening debate came in the form of the CAP RCT, published in JAMA in March 2018. It enrolled a massive >400,000 men, aged 50-69, over 573 primary care practices across the UK (by way of comparison the European ERSPC trial had ~160,000 men). The men were randomised to a single PSA test or no test and the median follow up was 10 years. Of those that had a valid PSA test 11% had a PSA level between 3 and 19.9 ng/mL, of whom 85% had prostate biopsy. Significantly more low grade prostate cancers (Gleason score ≤6) were detected in the PSA screened group compared to the unscreened group (1.7% vs. 1.1%). Overall there was no significant difference in prostate cancer mortality between the 2 groups. This contrasts with the ERSPC trial which did show some improvement in prostate cancer mortality in the screened group, but both these trials confirmed significant over diagnosis in the screened populations. Yes, there were a few criticisms of the CAP trial, in that only ~1/3 of men invited for screening had a PSA test which could have diluted any possible treatment effects, and the median was ’only’ 10 years and may be too short to see positive effects; but this is a huge study which significantly adds to the evidence base on this tricky subject.

The fabulous Richard Lehman in his BMJ blog said this was ‘one of the most important studies ever done in British primary care’, yet it was notable by it’s absence in terms of national press coverage, with some arguing that this was another example of publication bias against trials with ‘negative’ results (despite their importance in adding to the overall evidence base). 

So where are we with our advice to men who ask about ‘getting checked’ for prostate cancer. Well, in May 2018 the US Preventative Services Task Force reviewed and updated it’s recommendations on PSA screening, incorporating the CAP results, and I shall leave you with their conclusions which I think sums up the current state of play well:

‘For men aged 55 to 69 years, the decision to undergo periodic PSA-based screening for prostate cancer should be an individual one and should include discussion of the potential benefits and harms of screening with their clinician. Screening offers a small potential benefit of reducing the chance of death from prostate cancer in some men. However, many men will experience potential harms of screening, including false-positive results that require additional testing and possible prostate biopsy; over-diagnosis and over-treatment; and treatment complications, such as incontinence and erectile dysfunction.'

The topic of PSA testing, amongst other things, will be covered in our Men's Health webinar on Wednesday 23rd January 2019. To register for the webinar, or watch the recording click here.

This blog was originally written by Rob Walker and published via the NB Medical Hot Topics Blog, in July 2018. 


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