The decision of the health select committee that there will be no National Prostate cancer screening can only be described as short-sighted. Once again, the opportunity to create a world class preventative health program is slipping through our fingers. Conventional thinking, like that exhibited by Associate Professor Brian Cox of the Dunedin School of Medicine, dictates that the two cornerstones of prostate cancer screening – the digital rectal examination and the Prostate Specific Antigen (PSA) blood test – are both very unreliable. While this is superficially true, both tests producing many false positives and false negatives, the conclusion that prostate screening is not worthwhile does not necessarily follow from this.
The usual objection to large-scale screening is that such screening leads to “over-diagnosis” of prostate cancer and hence to much unnecessary treatment of “normal” prostates. This is an oversimplification. The real reason that there is much over-treatment of otherwise benign prostate disease is that there is a large overlap between benign prostate enlargement, pre-cancerous conditions and cancer itself. Even biopsy of the prostate (taking a small sample using a special needle) does not always provide a definitive answer. Most prostate cancer cells are very slow-growing and hard to differentiate from normal benign enlargement.
The equivocal nature of even a biopsy is the reason why studies of prostate screening programs yield equivocal results. The new Swedish prostate trial, mentioned in the quoted articles, is the latest one to cast doubt on the utility of a screening program. However, even a quick read through the abstract tells you that the screening program consisted of only a rectal examination for the first two examinations, with the addition of a single PSA for the third. No screening program designed today would rely on such a design.
The latest evidence on PSA screening for prostate cancer indicates that it is the velocity of PSA (how fast it is rising) that is important, rather than a single value. Any modern screening program would therefore incorporate an annual PSA with a rectal exam every, say, three years. A hard lump felt in the prostate or a rapidly rising PSA would be grounds for referral. Equivocal biopsies would then be regularly monitored by serial PSAs.
A screening program such as this has a good chance of making serious inroads into prostate cancer deaths. New Zealand could be the pilot for such a screening program. While it is possible that this may turn out to be a waste of money, there is sufficient evidence to make it a very worthwhile experiment. Currently, little is being done to try and reduce prostate cancer deaths in New Zealand and this has more evidence going for it than many other interventions, including most of our anti-smoking programs.
The thing is, compared to mammography for breast cancer screening, this kind of program is dirt cheap. It is worth doing even if it does turn out to be less successful than hoped. Over-treatment is not generated by the screening, but by the equivocal nature of the biopsy. It therefore makes little sense to suggest that only urologists should do PSAs, as restricting PSA tests to urologist will diminish referrals for potential prostate cancer. This will merely ensure that prostate cancer that would otherwise be caught early is not referred soon enough to save a life. The over-treatment issue should not be solved by a bizarre “see no evil” approach to prostate screening, but by improved methods of eventual diagnosis.
For the sake of a relatively small amount of health dollars, men’s health is once again being ignored. Seeing as I have yet to meet a urologist who is not in favour of regular PSA screening, one wonders who is advising the select committee and what their priorities are. I can’t help feeling that one would see a little more enthusiasm for a screening program if prostate cancer was not an exclusively male problem.