Читать книгу What Doctors Don’t Tell You - Lynne McTaggart, Lynne McTaggart - Страница 38

The most widespread screening test of all is the Pap smear, so called after a fellow named Dr George Papanicolaou who first developed it. In 1941, Papanicolaou and a colleague published a study demonstrating that malignant changes in the cervix could be diagnosed by examining cells taken from the vagina.⁴

This simple, relatively painless test involves scraping a small sample of tissue from the neck of the womb, smearing it onto a slide (hence the name), applying a fixative and sending the slide to a lab for analysis to see if any unusual cells are present. If the result shows any sort of abnormality, you are referred for further diagnostic tests, which usually include a direct examination of the cervix (a colposcopy) or a biopsy and even treatment for cancer.

It was first adopted in various Western countries after publication of results from the pilot screening programme in British Columbia showed that it was having an impact on lowering mortality rates. After seeing the British Columbia results, doctors began enthusing that the Pap smear would sound the death knell for cervical cancer.⁵

Under Britain’s current screening programme, some three million smears are performed every year at an estimated cost, if doctors, nurses and lab time are figured into the total, of at least £10 to £30 per woman screened.⁶ In the US, with one out of every eight women developing breast cancer, women’s groups are demanding action on all women’s cancers, including cervical cancer.

In response, the Centers for Disease Control and Prevention released the National Strategic Plan for the Early Detection and Control of Breast and Cervical Cancers (NSP), a collaborative programme between the Food and Drug Association, the National Cancer Institute, and the CDC. This promises to hot up the screening programme, increasing the number of women and the frequency with which they are screened for these diseases.

Although there hasn’t been an overall national government policy in the UK until relatively recently, most doctors in the UK regard cervical cancer screening as part of standard good practice, recommending that all women between the ages of 20 and 65 repeat the test every three to five years. The Lancet even recently recommended that the screening be extended to women over 65, now considered a high-risk group.⁷

Under National Health Service regulations, there is now more intense pressure on women to take the test with greater frequency as the fee per test becomes part of a doctor’s bread-and-butter work. Doctors in Britain get bonus pay only if more than 50 per cent of the women on their lists receive the tests, and triple the bonus pay if 80 per cent take it. But who would quarrel with the benefits of a simple, painless, risk-free test that promises to eradicate a common killer of women?

Nobody, if it actually worked. The problem is there is no convincing evidence anywhere to suggest that it does. Professor James McCormick of the Department of Public Health at Dublin’s Trinity College, an expert on mass screening tests, who studied much of the available medical literature on the subject, once declared: ‘There is no clear evidence that this screening is beneficial, and it may well be doing more harm than good.’⁸ By harm he means that many thousands of women are being subjected to risky treatments that could affect fertility for a condition they do not have or which could revert to normal.

First of all, it’s hard not to think, once you examine the figures, that medicine has backed the wrong horse. Cervical cancer is not the massive killer it’s often made out to be. Although some 2,000 women die from cervical cancer every year in the UK, that represents less than one-sixth of the number of women who contract breast cancer. In The Health Scandal, author Dr Vernon Coleman says that cervical cancer doesn’t even make the top 10 causes of death among women, falling behind breast, lung, colon, stomach, ovarian, even pancreatic cancers.⁹ And only 1.6 of every 1,000 women with abnormal smears go on to develop cancer.¹⁰

The smear test has also never been proven to save lives in any country where it has been introduced. In fact, every study shows that it is making virtually no impact. The only area in Canada where screening has been universally adopted is British Columbia; nevertheless, the death rate of cervical cancer there matches the death rate for the rest of the country.¹¹ Mortality rates from cervical cancer may have fallen in British Columbia, but they also fell in other parts of Canada without organized screening programmes.¹²

In the UK, the death rate from cervical cancer fell before the test was introduced and has stubbornly remained at the 2,000 figure (although several years ago, the government announced that the annual figure has dipped to 1,700). There is also no evidence to support the common contention that things would be worse but for the test. Dr McCormick and his colleague, the late Petr Skrabanek, say that the blind enthusiasm for cervical screening ‘has produced a climate in which it has been impossible to mount controlled trials’.¹³ Twenty years ago, Dr Herbert Green, a New Zealand doctor who had the temerity to dispute many dearly held assumptions about cervical cancer, was even found guilty of disgraceful misconduct for conducting a trial to see whether cancer is inevitable after an abnormal screening test.¹⁴

In the UK and the US, mass screening programmes like the National Cervical Screening programme have been launched without a consistent nationwide policy about when or whom to screen or how to follow up abnormalities.

Several years ago, an official study confirmed that cervical screening isn’t doing any good, since death rates from cervical cancer haven’t varied in two decades, despite virtually universal screening. These findings are based on monitoring nearly a quarter of a million women in Bristol over 20 years. In 1992, the death rate was similar to that of 1975, when continuous screening was introduced.¹⁵

If screening has managed to put a slight dent in the death rate nationally (and there is no hard evidence that screening is behind the rate’s dipping from 2,000 to 1,700), it comes at an unacceptable cost, says Dr McCormick. Many thousands of women are given false-positives and unnecessarily treated and possibly even left infertile or with terrible side-effects. During every area-wide screening in the Bristol area, 15,000 women were told they were at risk of cancer, and more than 5,500 investigated and treated for mild abnormalities which never would have progressed to cancer.

Between 1988 and 1993, nearly 226,000 women were screened, and abnormalities were supposedly found in more than 15,000 – or about one out of every 15 women. This figure is absurdly high compared with the actual rate of cervical cancer, which kills one woman in 10,000. The Bristol level of false-positives (where a ‘discovery’ of cancer turns out to be false) demonstrates to what extent cervical screening is simply causing unnecessary worry in healthy women.¹⁶

Over the years, the smear test’s reputation has been stained by a number of catastrophic errors. At Kent and Canterbury Hospital, for instance, more than 90,000 smears taken between 1990 and 1995 had to be rechecked, after eight women died following mistakes in reporting results. The problem, according to Britain’s National Institute for Clinical Excellence (NICE), is that the test is still appallingly inaccurate.

NICE estimates that up to 13 per cent of smear tests are false-positives and 20 per cent are false-negatives, where women with possible problems will have a test result come back as normal. In other words, out of 1,000 women screened, two women who could have cancer will be given the all clear. Other research has estimated a false negative rate of up to 60 per cent.¹⁷

In the US, the Centers for Disease Control and Prevention recently warned against annual Pap smear testing because of the high rate of false-positives, particularly for low-grade abnormalities, which result in potentially damaging treatment for symptoms which might have gone away if left alone.¹⁸ Even if screening were better set up in the UK and the US, the problem lies with the very medical foundation on which the test is based. Mounting evidence suggests that the smear campaign may be based on a faulty assumption: that abnormal, or ‘precancerous’, cells on the cervix lead to cancer. This assumption has been inferred from two facts: 1) that cervical cancer progresses slowly and, 2) if caught early enough, can be cured.

There are four categories of abnormal lesions, or ‘cervical interstitial neoplasia’: CIN I, II, III, and cancer. What we don’t know is whether the early lesions – those in the CIN I and II categories – will go on to develop cancer, or even what to do about them. In one study examining the accuracy of cytology (cell) screening, some 10 per cent of women screened had cervical abnormalities, ‘most of which’, notes Professor McCormick, ‘would not progress to cancer’.¹⁹

Medicine also doesn’t really understand the usual progression of this kind of cancer, a fact they have tacitly begun to admit. Some cervical cancers appear to regress if left alone, while others progress so rapidly that the three-to-five year gap recommended by most screening programmes would fail to pick them up in time. On this fragile foundation, women with an abnormal smear are frightened and stigmatized by the term ‘precancerous’ when no one knows whether it is appropriate or not.

This very situation happened to Anna. After her smear test came up positive, the 25-year-old spent months worrying that she had cancer. She also felt deeply embarrassed by the test results, as though it were a public comment on her sex life, since cervical cancer is known to occur among women who are highly promiscuous. In the end, she discovered that she had suffered all her distress for nothing. Follow-up tests some months later proved the first test was wrong.

One study in 1988 showed that nearly half of smears with mild abnormalities reverted to normal within two years. None of the patients developed invasive cancer during long-term follow-up.²⁰ Similar results occurred in a study in northeast Scotland, demonstrating that there is no steady progression from mild to moderate to severe abnormality of cells.²¹

A Canadian study showed that simple inflammation of the cervix may throw up an abnormal smear. Of 411 women examined by researchers at the Memorial University of Newfoundland, in St John’s, Newfoundland, the smear tests of nearly a third were shown to have inflammatory changes, nearly half of whom were shown to have some sort of infection. Ironically, even here the test was unreliable: half of the remaining women with normal smear tests also had an infection.²²

Besides this confusion over the significance of various results, the test is so inaccurate as to be virtually pointless. There is no guarantee that a Pap smear will pick up the fact that you have cancer, and a fair likelihood that you will be told you have an abnormality that doesn’t actually exist. In one study, the authors admit to false-negative rates of between 7 and 60 per cent.²³

In another report, one in every five cervical cancer deaths was due to poor management or misdiagnosis by doctors. In one in every seven of these cases, the smear tests had been read as normal. Re-analysis of the slides showed that early abnormalities had in fact been present, but were missed.

Interpretation of the results varies wildly, depending on who is looking at the slides. You could even get a different interpretation from the same person looking at the same slide on separate occasions. This is particularly so, says Professor McCormick, with the minor changes that give rise to most reported abnormalities.²⁴

A report from the National Audit Office, ‘Cervical and Breast Screening in England’, found a wide disparity in interpretations of findings and a lack of benchmarks against which to compare results. The audit found that in some areas of England, nearly a fifth of all smears were classified as abnormal, compared with 3 per cent in other areas.²⁵ This lack of any standards is responsible for many false diagnoses of cancer.

In Scotland, some 20,000 tests done under the screening programme at the Inverclyde Royal Hospital had to be re-examined after evidence that the doctor doing the analysis may have misread the results. On a preliminary re-examination, 40 out of 1,000 smears taken since 1988 were found to be ‘inadequate’ and to require a repeat test.²⁶

The Scottish debacle is only the latest in a series of such incidents in the UK. In 1987, in Liverpool, 45,000 tests were re-examined and 911 found to have been wrongly diagnosed. In 1988, in Manchester, a batch of 3,000 tests passed as clear were re-analysed and 60 found to be suspect.

Large numbers of smears are also technically not up to scratch. Dr Chandra Grubb, head of the Department of Cytology at the Royal Free and University College Hospital in London, estimates that some 10 per cent of all smears sent to cytology departments are useless, and a further 40 per cent are of limited usefulness because doctors haven’t taken the smear correctly or have taken it from the wrong site.²⁷ With this kind of terrible batting average, the likelihood is that screening not only isn’t going to pick up your cancer, but could set you on the road to potentially risky treatments when you don’t need them.

The conventional treatment for early ‘precancerous’ lesions employs a colposcopy (a magnifying glass with a light) and biopsy (exploratory surgery), diathermy (burning the abnormal cells) or cytotherapy (which employs a freezing probe to freeze the outlaw cells). These procedures can all cause haemorrhage or permanently damage the cervix, resulting in an ‘incompetent’ or narrowed cervix, and thus affect a woman’s chances of carrying a baby to term.

Dr Robert Mendelsohn liked to tell the story of a colleague of his whose wife received a positive reading. She went ahead with a cone biopsy, which caused such excessive bleeding that she had to have an emergency hysterectomy, during which she almost died from the anaesthesia. All because of a test that might have been wrong in the first place.²⁸

One of our readers, a young woman in her early twenties, had been diagnosed as having stage 2–3 abnormal cells, and was scheduled for an operation to have them frozen or burned out. At the eleventh hour, she decided to have a second smear test at another laboratory. Her new test showed that the first test was wrong; her problem turned out to be a simple infection.

Individual doctors also differ widely in their views of how to treat abnormalities. The British National Audit Office report showed that many doctors opt for radical treatment such as cervical conization for cases of mild abnormalities, which would eventually resolve themselves without intervention.²⁹

Some reports demonstrate that getting in there early and aggressively treating cervical abnormalities doesn’t do any good, anyway. In one recent study, referring women with mildly abnormal smear test results for the more invasive examination produced no more favourable outcome than adopting a policy of watchful waiting. Referring women for a colposcopy exam, often with a biopsy, or simply giving them a repeat smear test after several months produced identical results: 1.6 per 1,000 cases developed into cervical cancer. This means 2,500 women were sent for colposcopy – with its inherent risks of causing infertility – to save one case of cancer.³⁰

Because of the high rate of false-positives, some countries like the US and Switzerland have now introduced a new technology called ‘liquid-based cytology screening’ (LBC), also known as ‘monolayer cytology’. The specimen is collected by a special spatula, the head of which is rinsed into or broken off into a vial of preservative, so that the entire sample is immediately preserved in liquid.

The UK’s own pilot studies showed that LBC produces more accurate results, with only 1.6 samples considered ‘inadequate’, or unable to be read, compared to more than 9 per cent of traditional Pap smear slides.

Nevertheless, there is some evidence that the LBC test is even less reliable and more likely to give false-positive and false-negative results than the conventional variety: 87 per cent, compared with 91 per cent for ordinary Pap smears.³¹

This questionable batting average has not deterred the UK government. In October 2003, it announced that LBC would be ‘rolled out’ over the next five years, with the intention of replacing the conventional Pap smear test, at a cost of some £10 million.

The National Co-ordinating Network now specifically recommends that women with minor cell abnormalities – ‘borderline or mildly dyskarotic smears’ – adopt a path of surveillance – that is, have the smear test repeated six months later. The women should only be referred for colposcopy if the smear continues to show abnormality. At very least, according to the US CDC, waiting an interval of three years (or five years, if you are over 50) won’t affect mortality rates. If you do get a positive reading, insist on a repeat smear from another lab before going down the more invasive route of biopsies and worse.