Читать книгу What Doctors Don’t Tell You - Lynne McTaggart, Lynne McTaggart - Страница 39

Mammography – an x-ray of the breast designed to pick up early malignancies – is the other screening test being stepped up sharply. Breast cancer, the biggest lady-killer after lung cancer, claims the lives of an estimated 40,000 American women every year;³² some 33,000 new cases are diagnosed every year in the UK – double the incidence of the 1950s. As cases continue to spiral upward (one in nine women contract it in the US, and one in twelve in the UK), the pressure is on for women, particularly those over 40, to have regular screenings, and mammography has become a huge growth industry.

Despite decades of enormous government resource and a massive money-spinner aimed at efforts to improve early detection and local treatment, the bottom line is that the level of breast cancer mortality has remained constant.

Breast cancer deaths in England and Wales fell by 12 per cent in the 1990s. Nevertheless, health officials who ascribe this sudden drop to their extensive mammogram screening programmes have no reason to be self-congratulatory. New research has discovered no evidence to link the two, although screening has helped detect more cases earlier. The National Cancer Registration Bureau believes the fall may be more likely associated with the increasing use of the drug tamoxifen, which slows cancer growth, than with any screening. Since nationwide screening was introduced in 1988, recorded incidence of the disease in the 50–64-year age group rose by 25 per cent.³³ Furthermore, the fall in mortality began in 1985, but the first NHS screening units were not working until three years later, and Great Britain as a whole wasn’t sufficiently covered until 1990. As Royal Marsden Hospital breast cancer specialist Michael Baum writes, claiming that any part of the drop in mortality is due to the screening programme is ‘intellectually dishonest’.³⁴

After the publication of a Swedish meta-analysis some years ago, which pooled results from five studies conducted over five to 13 years on some 300,000 women, most members of the medical establishment have adopted as gospel its results: that for women 50 and over, regular screening can reduce breast cancer mortality by 30 per cent.³⁵ It is also generally agreed that no studies have shown a benefit for women younger than 50.³⁶ In the UK, the government offers mammography to women aged 50–64, and invites them to participate every three years.

This ‘30-per-cent risk reduction’ has been adopted as a mantra by the medical profession. It has provided a justification of sorts to screen many groups, such as women under 50, where benefits of screening have never been shown. Despite all medical evidence to the contrary, the American Cancer Society and the American College of Radiology have carried on urging all women over 40 – which of course includes this limbo group between the ages of 40 and 49 – to have annual mammograms.³⁷

But even among the over-fifties, there is no conclusive evidence that mammographic screening is doing any good. In the much-quoted Swedish study, the researchers came up with their figure by pooling all the results of three bands of age groups – the 40–49-year-olds, 50–69-year-olds and 70–74-year-olds – into an overview. The study showed a positive benefit (29 per cent reduction in mortality) among the women in their fifties, but none among the women in their forties or those in their seventies.

However, when you actually examine the science behind these statistics, this is the only study to show clear benefit, even among the 50-year-olds. The 30 per cent improved survival figure being bandied about derives from several articles which examined all the studies of screening and attempted to pool the results. Although most studies didn’t show a clear benefit, the article concluded that those that were most scientific, or ‘randomized’ (that is, women assigned randomly to either screening groups or controls) all proved to be of benefit.³⁸

However, Dublin’s Dr McCormick and his late colleague Petr Skrabanek, both scourges of unproven medical practice, have pointed out that three of the four of those trials considered most scientific ‘failed to reach statistically significant benefit for women aged 50 and over’.³⁹ These included two studies of an aggregate of 80,000 women, which were dismissed as ‘too small’ by one set of screening proponents.⁴⁰ In other words, to reach their favourable statistics, academics have combined entirely different types of scientific studies – those that set out with several groups of women to see what happens to them over time, versus analysing what has already happened to several groups of women – in an attempt to make the insignificant advantages of screening appear significant. In fact, two of the best breast cancer centres in the UK failed to lower deaths significantly using annual clinical exams and every-other-year mammograms.⁴¹

It’s also wise to keep in mind what this 30 per cent supposed reduction in mortality actually translates into. At best, it may prevent or postpone one cancer death for between 7,000 and 63,000 women invited for screening every year.⁴²

More recently, researchers from the University of British Columbia in Vancouver studied all the trials since the early ones that claimed a 30 per cent reduction in deaths from breast cancer in women over 50. There has been far less publicity, the Canadian researchers point out, about all the studies that have been done since those early days, showing that mammography does no good for anyone in any age group, but does great harm through false-positives and get-in-there-early intervention. They attacked mammography and indeed recommended that they be junked altogether after discovering that only one in 14 women with a positive mammogram result indicating breast cancer will actually have the condition.

‘Since the benefit achieved is marginal, the harm caused is substantial, and the costs incurred are enormous, we suggest that public funding for breast cancer screening in any age group is not justifiable,’ these epidemiologists concluded.⁴³

In another Canadian study, when six trials of breast cancer screening were analysed, only one in 14 women with a positive mammography result indicating breast cancer actually had the condition. As with cervical cancer, this means that many women are going through needless worry and treatment on the basis of an inaccurate test.⁴⁴

The latest evidence concurs that regular mammograms offers no survival advantage among any age group under 60.⁴⁵ In 2002, after studying all the most recent science, a committee of US cancer experts called the The Physician Data Query board (PDQ) concluded there is insufficient evidence to show that mammograms actually prevent deaths.⁴⁶ More than one-third of mammograms give false readings overall, two-thirds false-positives,⁴⁷ and the test is accurate less than half the time and only in the second half of a woman’s menstrual cycle.⁴⁸

The rationale for screening has always been that the earlier you catch it, the smaller the tumour will be, and hence the greater your chances of beating the disease. However, this rationale doesn’t take into account that cancer doesn’t always metastasize at the same rate. Breast cancer isn’t a tidy disease that progresses in the same way for every woman; sometimes it spreads throughout the body, other times it advances in the breast alone. Much of our treatment doesn’t influence the outcome in any case.⁴⁹

One reason may be that mammograms actually increase mortality rates. Among the under-fifties, more women die from breast cancer among screened groups than among those not given mammograms. The Canadian National Breast Cancer Screening Trial (NBSS), published in 1993, which screened 50,000 women between the ages of 40 and 49, showed that more tumours were detected in the screened group, but not only were no lives saved, but a third more women died from breast cancer in the group first offered screening.⁵⁰ Similar results occurred in three Swedish studies⁵¹ and also in those conducted in New York.⁵² One of the Swedish studies, conducted in Malmo, showed nearly a third more cases of breast cancer in women under 55 given mammograms over 10 years.⁵³ Even when you adjust results and allow that cancers among women aged 51–69 – the so-called ‘high-risk group’ – have been detected, screened women have nearly a 2 per cent higher incidence of breast cancer than controls.⁵⁴

That more younger screened women die may reflect the fact that mammography is indiscriminant, picking up many cancers which would do no harm if left alone. The scattergun nature of the technology has several implications. This ability to pick up any sort of tumour falsely increases the incidence of breast cancer by a quarter to a half.⁵⁵ Adding all these benign tumours, which of course don’t lead to death, into the cancer data also has the effect of making it look like more people in the screened population survive because of early detection.

By picking up all and several tumours of every variety, mammograms also could be falsely inflating the incidence of breast cancer by as much as one half.⁵⁶

The third effect of regular mammograms is that they lead to massive, unnecessary treatment because benign tumours are often mistaken for malignant ones. In one study of over a thousand women undertaken by Harvard Medical School, only a quarter of the women whose mammograms had recorded some abnormality were actually found to have malignant tumours. Other radiology departments referring patients to the Harvard Center had an even worse batting average – getting it right only one-sixth of the time. And of course an inappropriately strong mammography report, which might include statements such as ‘malignancy cannot be excluded’, raises the anxiety level of the patient and referring physician and often ends up with the woman on the operating table.⁵⁷

Routine screening is undoubtedly responsible for the huge increase in the aggressive treatment of ductal carcinoma in situ (DCIS) – some 40,000 cases in the US alone.

Since the advent of screening, the incidence of DCIS has sky-rocketed, from 2.4 per 100,000 women in 1973 to 15.8 cases per 100,000 in 1992.⁵⁸ Although many women being diagnosed with DCIS are undergoing radical mastectomies, this abnormality, or ‘pre-cancer’ is ‘not a synonym for other forms of cancer’, says Professor McCormick. Not only do many experts misunderstand DCIS, but most cases of this condition, says McCormick, would not do a woman any harm.⁵⁹

Up until now, only relatively high doses of radiation have been associated with an increased risk of breast cancer. However, new evidence demonstrates that even moderate strengths of strong x-rays raise the risk of breast cancer five or six times in women who carry a certain gene, occurring in about 1 per cent of the population – or in at least one million American women. In 1975, Dr C. Bailar II, editor in chief of the Journal of the National Cancer Institute, concluded that accumulated x-ray doses in excess of 100 rads over 10 to 15 years may induce cancer of the breast.⁶⁰ A single-view mammogram offers the average breast a dose of about 200 millirads (0.2 rad).⁶¹

However, women with the ataxia-telangiectasia gene, says Dr Michael Swift, chief of medical genetics at North Carolina University, have an unusual sensitivity to radiation and could develop cancer after exposure to ‘appallingly low’ doses. He estimates that, in the US, between 5,000 and 10,000 of the 180,000 breast cancer cases diagnosed each year could be prevented if women with the gene were not exposed to the radiation from mammograms.⁶²

Just four breast films (the usual pictures for one mammogram session) expose you to 1 rad (radiation absorbed dose) – about 1,000 times more than that of a chest x-ray. Each rad increases the risk of a premenopausal woman’s cancer risk by 1 per cent, so that women screened for over a decade would have raised their cancer risk by 10 per cent.

Besides a genetic susceptibility, the physical trauma caused by the force of mammograms could be a factor in spreading cancer. At the moment, mammograms use 200 newtons of compression, the equivalent of 20 1kg bags of sugar per breast. Some of the modern foot-pedal operated machines are designed to exert one-third again as much force – the equivalent of your breast being squashed by 30 bags of sugar.⁶³ The force is thought to be necessary in order to get the best quality of image while keeping the radiation dose to a minimum.⁶⁴ A number of researchers believe that compression during mammography can rupture cysts and disseminate cancer cells.⁶⁵ This phenomenon has been observed in animal studies; if a tumour is manipulated, it can increase the rate of its spread to other parts of the body by up to 80 per cent.⁶⁶

Many biopsies to investigate a suspicious lump found on mammography have their own set of problems. In this standard procedure, a thick needle is inserted into the breast under local anaesthetic to remove a small piece of tissue. This is then examined for cancerous cells. In one study of women undergoing biopsy, a quarter had problems afterward with the wound left by the needle such as infection or bleeding. Nine patients reported a new breast lump (all benign) developing under the biopsy scar between one to seven years after surgery. Eight patients continued to have pain in the area where the biopsy had been taken up to six years after the operation, and seven reported unsightly scars.⁶⁷

Fine-needle aspiration, which can be done on an outpatient basis, has been served up as the less invasive alternative when a lump has been found; in this instance, a fine needle with a syringe is inserted in the breast to draw out a specimen of the lump’s contents. However, doctors have been known to puncture the lung during this procedure, causing pneumothorax (in which air enters the chest, causing the lung to collapse). In 74,000 fine-needle aspirations of the breast, this occurred in about 133 patients (0.18 per cent).⁶⁸

The experience in many countries suggests that mammograms also have a high rate of inaccuracy. In Canada, during the first four years of the eight-year trial on breast cancer screening, nearly three-quarters of test results were unacceptable. Only in the last two years of the trial were more than half the tests up to the required standard.⁶⁹

As for women under 50, another Canadian study showed that some 87 per cent of so-called cancer cases detected by mammograms were false alarms.⁷⁰

The high level of false-positives is partly due to poor standards in equipment. A third of women’s clinics in the US were not accredited, as of early 1994. The FDA admitted that many of them were inaccurately reporting mammograms and that some women were receiving doses of radiation that were far too high.⁷¹ Just how poor the standards are was revealed by a 1989 survey of a cross-section of mammography units carried out by the Department of Health in Michigan. One-third of the units studied routinely exceeded the various standards of radiation exposure.⁷²

The US aimed to correct this problem with the Mammography Quality Standards Act, passed in October 1992, which was to establish quality-control standards and a certification system for the more than 10,000 medical facilities that perform and interpret mammograms. These quality-control standards relate to the training and education of personnel, the equipment and the dosage used, among other criteria. Doctors would also have to have continuing education in reading mammograms and be expected to interpret an average of 40 mammograms a month.

As of October 1994, every facility performing mammograms had to obtain a certificate or provisional certificate to continue to operate legally.

However, although setting standards has undoubtedly improved some of the appalling mistakes made in the past, it may do nothing to improve the inherent imprecision of the technology itself. Even mammograms of the best quality can be misread by highly experienced radiologists. In one study carried out by Yale University, 10 seasoned radiologists, with 12 years’ experience in reading mammograms, each given the same 150 good-quality mammograms, differed in their interpretation a third of the time. In a quarter of cases they also radically disagreed over how the patients should be managed (such as whether they should have follow-up mammograms or exploratory surgery). Even among the 27 patients later definitely diagnosed as having breast cancer, the radiologists varied widely in their diagnosis. Nearly a third of cancers were wrongly categorized. One radiologist did not detect a cancer that was clearly visible, while another thought it was developing on the breast opposite the one where it actually was.⁷³

Even if regular screening doesn’t spread or cause cancer, its dubious benefits may not be worth the pain reported by a third of women undergoing the screening.⁷⁴ Helen, from Westcliff on Sea, now in her early fifties, has suffered with lumpy breasts and severe mastitis for 20 years. She’s had several routine ‘horizontal’ mammograms and a fine-needle aspiration of a cyst she found 12 years ago. Then, in 1991, she had another mammogram. ‘This time I had to stand upright and each breast was squashed vertically against the machine. The pain was excruciating. Tears welled up in my eyes and I could hardly stop myself from shrieking. The pain lasted in both breasts for three or four days before gradually subsiding,’ she says.