I had just written about mammography screening, and how decades of research show that while it detects more breast cancers, it doesn't reduce overall deaths.

During the discussion, someone raised the issue about prostate cancer screening and the PSA test.

It was a fair question — because the parallels with routine mammography are striking. Both programs rest on the same seductive logic: find cancer early, treat it, and save lives. It sounds so obvious, doesn't it?

But the latest data on prostate-cancer screening — 23 years of it — suggest that this promise, too, has failed the most important test: overall mortality.

When the Numbers Don't Match the Promise

The European randomised screening study began in 1993 and enrolled more than 160,000 men aged 55 to 69. Half were invited to have regular PSA blood tests; the others were not.

After 23 years of follow-up, published in the New England Journal of Medicine, the results are just in.

Predictably, screening led to about 30% more prostate cancers being diagnosed. However, most were low-risk tumours that never would have caused harm.

Men who were screened had a 13% lower risk of dying from prostate cancer than those who weren't screened.

But that difference, while sounding impressive, shrinks dramatically when translated into absolute numbers: 1.4% versus 1.6%, an absolute reduction of 0.2% (see graph).

That means you'd have to screen about 500 men to prevent one death from prostate cancer — the other 499 see no benefit.

But here's the key point — the overall death rates were identical in both groups (see graph below).

Despite finding more prostate cancers, men who were screened did not live longer — they simply had a higher chance of being labelled "cancer patients."