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Screening for prostate cancer – evidence vs wisdom

The UK currently operates a policy not to offer routine PSA screening to men. It is an interesting decision, particularly if you are a man of a certain age and starting to think about your future.

You may be worried to know that across London an average of 385 men with prostate cancer are diagnosed via emergency presentation every year and in NW and SW London combined 491 men presented late with stage 3 or 4 disease. This isn’t particularly clever for a disease that takes a long time to progress and reflecting that at stage 4 the 5 year survival is probably less than 30%.

I can appreciate that PSA is not always raised in prostate cancer and that there are other reasons why PSA might be raised – so there are false positives and false negatives. It can also not differentiate from a slow growing tumour and the much more dangerous aggressive form. Once a man has an elevated PSA the next stage of the examination may be a repeat test and then a digital rectal examination to actually feel the gland. From that point the investigations usually become much more invasive and there is a significant impact on a man who has these investigations. This has driven the risk-benefit analysis in some studies to a point where screening is not recommended.

Recently I was impressed of a report about multi-parametric MRI which appears to be a much more effective tool, preventing men from having a needless biopsy and all the associated side effects. I also understand that there is a program in place to make this test much more available which can only be a good thing. Perhaps this is one factor in reconsidering the evidence or applying different wisdom?

The largest study in Europe first published in 2009. At this point 182,000 men had been screened every 4 years and compared to a control. The cumulative incidence of prostate cancer was 8.2% in the screening arm versus 4.8% in the control group. Screened patients were more likely than control patients to have organ-confined (clinical T1-2) disease, non-metastatic disease, and lower Gleason Score (≤ 7) at diagnosis. This translated into a decreased risk of prostate cancer mortality among the screened patients, with a risk ratio of 0.85. In more practical terms, to prevent one prostate cancer death, the number needed to screen (NNS) was 1,410, and the number needed to treat (NNT) was 48.

At this point it is worth considering a number of factors. Prostate cancer is one of the most common cancers in men with approximately 40,000 new diagnoses each year so screening would need to be widespread. Generally, prostate cancer is slow growing and, from the point of diagnosis, clinical trials comparing active treatment to watchful waiting have taken 8 years before the two mortality curves start separating and at 10 years there is still no statistically significant difference. However until these data mature further we won’t really know what effect delaying treatment has on later quality of life and survival at perhaps 15 years. Just because we know that after diagnosis of non-aggressive prostate cancer in an early stage most men will survive to 10 years – it doesn’t help me plan for 20 years.

When you roll forward the data from the European study to 13 years then the NNS falls to 781 and the NNT to 27. It is unknown how much further these numbers will drop with additional years of follow-up, but it seems likely that the observed magnitude of screening benefit to reduce prostate cancer mortality will continue to improve as data from this study continue to mature.

It is interesting talking to men about this issue. In reality a proportion of the men I speak to don’t know where their prostate gland is, yet they all seem to know of someone who has prostate cancer or who has died from prostate cancer. I might be a supporter of watchful waiting, but I can’t exercise that option until I have a diagnosis.

It is clear that men need to understand the facts as they stand and then think about it – evidence to wisdom. And they need to think about themselves, understand their risk and whether they want to know or not. There will be men that would rather not know and will not see a doctor even if they have severe symptoms. I don’t understand this approach. Nor do I understand people saying – don’t worry about the PSA, but watch out for symptoms and go and speak to your GP.

I think that the risk benefit balance has already shifted significantly. We can’t really stand still because the PSA is not a perfect screening test and wait for a better screening test to become available. It may be significantly more expensive and the risk benefit analysis may lurch to the point where it is still not considered cost effective.

I abhor the general view that I might get worried – so it is better not to tell me about screening. It is my prostate and my money. Better to be honest and say that for the few patients we might find and what they might have to go through to get a proper diagnosis – it will require a lot of organisation and it’s not worth spending tax payer’s money on it.

Perhaps community pharmacy has the answer by offering a simple qualitative non-diagnostic PSA screen at the man’s expense. It is my responsibility to look out for myself and if I have prostate cancer then I will get to know early.

 

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About markmandc (250 Articles)
A pharmacist with experience working in secondary care, primary care, community pharmacy and general practice.

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