SMEARS, IDLE SMEARS
no one knows whether cervical smears do any good anyway
THE furious storm that has broken over the head of the former Liverpool patholog- ist, Dr Kathleen Lodge, serves to empha- sise the high emotion associated with the subject of cancer, and in particular cervical cancer.
The popular and populist explanation of what happened at Liverpool Women's Hospital holds that Dr Lodge misdi- agnosed more than 900 abnormal cervical smear tests and that, as a result, more than 900 women found themselves at unneces- sary risk of cancer. Now that the error has been exposed, the anguish of the women forced to return for additional tests, and in some cases treatment, excites our sym- pathy, outrage and, as the demands for extra funding suggest, inevitably comes to touch our pocket-book. Conventional wis- dom maintains that cervical cancer screen- ing is 'a good thing', and that if we only threw enough resources at the problem then thousands of unnecessary deaths could be averted.
While anyone with an ounce of humanity must sympathise with this goal, the effec- tiveness of the method is open to question. The present enthusiasm for cervical screen- ing may be traced back to the late 1940s and early 1950s, following the introduction of the Papanicolaou (abbreviated to Tap') test.
The medical scientists of the time, conscious of the appearance of cancer under the microscope, set out to catch the disease at an early treatable stage. They noticed that the tissue lining the inside of the cervix sometimes appeared disorga- nised and abnormal on examination, but fell short of displaying the full characteris- tics of a cancer. Nevertheless, the resembl- ance to true malignancy convinced many of the investigators that they were dealing with a `precancerous' state. Conviction led to therapy and some would say, therapy to conviction.
It rapidly became and continues to be the accepted wisdom that it is unethical to leave such 'cancers' untreated; this despite the lack of evidence that conversion to full invasive cancer is a natural consequence of having a `precancer'. It has been pointed out that the only way to establish such a progression would be to leave a large number of women with abnormal smears untreated and in ignorance for a follow-up period of possibly 15 years or more. While such a programme would help clarify the issue, all sides agree that it would save no lives and would thus be an ethically im- possible experiment.
The real argument, of course, turns not on the laboratory appearance of a few slides, but on whether or not cervical screening is actually successful in reducing the death rate from cervical cancer. At a superficial level this would appear clearly to be the case. In most Western countries the death rate from cervical and associated cancers has fallen steadily since tke war, and this progress has gone hand in hand with the wider use of cervical screening.
The death rate from these cancers has, however, been falling steadily since well before the introduction of any smear test- ing programme. In an analysis of previous trials by Drs Apostolides and Henderson, published in the journal Cancer a decade ago, the scientists noticing this trend found it impossible to determine what proportion of any decline in mortality could be attri- buted to preventive screening and how much to the steady post-war improvement in general hygiene and medical care.
More modern work, examined in a Lancet editorial two years ago, came to much the same conclusion. Some studies have consistently demonstrated that within a given country patients who attend for regular screening do better than those who do not. But these findings have been confounded by the vagaries of patient self-selection. It is disproportionately the articulate and affluent who regularly turn up to screening clinics, while much of the increased burden of risk is known to be carried by the poor and ill-educated. Once adjustments have been made for these and other sampling errors, in most of the reported studies the benefit of screening evaporates.
It is argued by some that funding for an improved cervical screening service should not be withheld because of an historical inability to identify a specific benefit. A young gynaecologist (a believer in the benefits of screening), in a letter to .the British Medical Journal last Februry, advo- cated a massive increase in the British programme in advance of a demonstrable fall in mortality rates. Part of his argument rested on the recent observed great in- crease in the numbers of people found with `precancers', with the possibility that there might be a surge in the number of full cancers appearing in years to come.
This lends an urgency to the whole problem. If it does take up to 20 years to demonstrate a solid benefit from a screen- ing programme, then if we hesitate until we are certain of this advantage, we may well have condemned thousands of women to unnecessary disease,' distress and prema- ture death.
This is a perfectly respectable medical point, but it raises the questions of how resources should be allocated. Is the cost of a programme, taking into account the lost opportunity to treat other diseases, worth the possible benefits gained? Doctors in general (myself included) tend to see them- selves as advocates for their patients, not as agents of administration or government. So it is easy to regard one's own patients, and by extension all those in one's own speciality, as exclusively worthy of funding and backing. This is quite natural, but there are more demands for funds to prevent sickness than there is money avail- able.
How should the community allocate it? A ten per cent fall in the number of people dying from cervical cancer might save around 200 lives a year; a similar advance in breast or lung cancer treatment might save an annual 1,200 and 3,500 people a year respectively. A ten per cent drop in deaths from heart disease could save 15,500 from death every year.
The view that medical therapies must justify themselves in terms of lost opportu- nities for treatment, brings us back full circle to the Liverpool case. Most people are able to identify with the victims of this error, whether directly or through the fear that a loved one may suffer a similar medical misdiagnosis and be left to carry the incubus of cancer. Fear, sympathy and, paradoxically in this context, a respect for expert opinion, has led us collectively to suspend our powers of disbelief. We accept that cervical smear testing is 'a good thing', that the emotional traumas that the pa- tients are milled through is justified in terms of the benefits obtained. We believe these things but do we really know them to be true?
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