Dee GP – Private General Practice in West Kirby

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Prostate Cancer Screening

Prostate cancer screening was in the news at the end of November. I really want to separate the concept of prostate cancer screening from the technology of PSA testing but this distinction has been lost in the media. Since 2001, the UK has had the Prostate Cancer Risk Management Programme (PCRMP). This is not a screening programme – it is just supposed to support GPs to provide PSA tests to men who request them, after a conversation about benefits and limitations.

The problem with PSA testing

PSA is made in the prostate gland, and is normally detectable in low levels in men’s blood. If you take a group of thousands of men, you can easily see that men with prostate cancer have a higher PSA on average. However for an individual, a PSA measurement is not very useful. A slightly above average PSA doesn’t mean you’re particularly likely to have prostate cancer, and a below average one doesn’t mean you don’t have prostate cancer.

PSA
(ng/mL)		 Default interpretation Context
≤ 1.5 “Normal” result Prostate cancer very unlikely ≈ 50% of test results
1.5 – 3* 30-50% of all clinically significant prostate cancers ≈ 50% of test results come back in this grey zone
3* – 20 Abnormal result PSA false positive rate ≈80%
≥ 20 Prostate cancer very likely <1% of test results

* Since PSA increases with age we increasingly use age-adjusted thresholds rather than a fixed value of 3 for all men. Whatever threshold is used though, there is always a balance between missing significant cancers and raising alarms unnecessarily. That trade-off exists with every medical test, but with PSA it has proven particularly difficult to achieve an acceptable balance.

Stockholm3

Stockholm3 is a blood test to predict risk of prostate cancer in people aged 45 to 74 years with no previous prostate cancer diagnosis. It estimates the risk as a percentage using a (proprietary) formula that incorporates 5 plasma protein markers (including PSA and free PSA), 101 genetic markers and some clinical data such as age, family history and previous prostate biopsy.

Stockholm3
(risk percentage)		 Interpretation
≤ 3% Retest in 6-10 years ≈ 50% of test results
4-10% Retest in 2-4 years
≥ 11% Refer to specialist – MRI & biopsy

In Swedish, Norwegian, Danish, German, Swiss, Canadian and US studies, adoption of Stockholm3 was associated with an increase in detection of curable cancers, and a reduction in advanced / metastatic cancers. (It also reduces detection of low-risk cancers, the ones that wouldn’t have caused harm anyway.)

Stockholm3 costs £350 and we can take your blood samples at Dee GP.

The future for the NHS?

Many professional bodies have been urging for a full screening programme with PSA testing and the UK’s National Screening Committee has made draft recommendations that are now out for consultation. It ‘only’ recommended screening men with confirmed BRCA1 or BRCA2 gene variants. No population screening, no targeted screening of Black men (who are twice as likely to get prostate cancer) and no targeted screening of men with family history. It does support the £42 million TRANSFORM trial, the biggest prostate cancer screening trial in 20 years, which is going to compare:

The investigators have the capability to vary their trial protocol in order to investigate other tests. As an outsider, it’s not clear to me whether they are investigating Stockholm3, but I don’t think they are. Clearly there is some overlap between the genetic testing in the trial and the genetic component of Stockholm3. I infer that they think the quick MRIs are very promising

Prices

Test Price
Total PSA alone £75 (not recommended, available on NHS anyway)
Stockholm3 £350 to measure Stockholm3
(Or just £75 if PSA <1.5)

Disclaimer

This article is about screening for cancer. Always seek prompt medical attention if you have any symptoms of cancer. Symptoms of prostate cancer are: