Breast cancer

09 April 2010

Mammograms: to screen or not to?

Debate still rages about whether women are getting the right information on the merits and risks of mammograms. So should you, or shouldn't you? Professor Apffelstaedt weighs in.

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It's not hard to find a breast cancer survivor who thinks routine mammograms are a good idea. Almost any woman who had a cancerous tumour detected in her breast during a regular screening appointment would probably think the scan -- and subsequent surgery, radiotherapy or chemotherapy treatment to remove the cancer -- saved her life.

But that is not always true and an increasingly heated international debate is raging about whether women are getting the right information on the merits, and risks, of mammograms.

The fear is that over-diagnosis -- when screening picks up tumours that would never have presented a problem -- may mean many women are undergoing unnecessary radical treatment, suffering the physical and psychological impact of a breast cancer diagnosis that would otherwise not have come up.

Row erupts

While some scientists are locked in battle, slinging accusations at each other of misleading data and conflicts of interest, others say the row itself is a signal that it's time for a new and more refined approach to breast cancer screening.

"What really bothers me... is the poor women who are the subjects of this debate, who must be utterly confused and not know what the hell is going on or what to do," said Michael Baum, the doctor who introduced Britain's first breast screening programme more than 20 years ago. "To carry on regardless is no longer acceptable. I'm trying to find a way out of this mess."

Low level argument over the merits of mammograms has bubbled for some years, but a political storm blew up in the United States last year when public health officials questioned whether screening for women in their 40s actually save lives and proposed upping the regular screening age to 50.

Now, in Europe, two recent scientific studies have brought the issue to a head, pitting convinced breast cancer screening supporters against those who say the numbers just don't add up.

Confusing studies conflict each other

A team of Danish scientists published a study showing that breast cancer screening programmes of the type run by health services in Europe, the United States and other rich nations do nothing to reduce death rates from the disease.

A week later, a British team published a study showing a "substantial and significant reduction in breast cancer deaths" due to screening.

The lead researchers on each paper, Stephen Duffy of Queen Mary, University of London, who led the British study, and Peter Gotzsche of the Nordic Cochrane Centre, who led the Danish team,said they suspected the other of having long-held biases on breast cancer screening that skewed their work.

At the heart of the matter is the issue of over-diagnosis. This is when a mammogram picks up something called ductal carcinoma in-situ (DCIS), which are cells -- often described as "pre-cancerous" or non-invasive -- that may progress into life-threatening cancer if left untreated.

The problem is, there is also the chance they would never progress or cause a problem, but instead leave the woman to live in blissful ignorance and die years later -- but not of breast cancer.

The fear is that regular population-wide screening programmes are causing over-treatment of such cancers, ruining women's lives with unnecessary mastectomies or chemotherapy.

One size doens't fit all

Gotzsche's evidence suggests that for every 2 000 women who are screened over 10 years, only one stands to have her life saved by the mammogram programme, whereas the risk of getting an unnecessary breast cancer diagnosis is 10 times that.

Duffy's study, meanwhile, found that screening saves two women's lives for every one who is given unnecessary treatment.

"I have never in science seen such a huge discrepancy, and Stephen Duffy's estimates are simply blatantly wrong," Gotzsche said when asked about the difference.

For his part, Duffy accuses Gotzsche's team of spending years pursuing research that finds against the merits of breast cancer screening, yet has failed to change opinion.

"Most of the people who work in breast cancer... are actually pretty happy with screening. That's why we get paper after paper from the Danish Cochrane team, and yet the screening programme stays," he said. 

Yet other experts say the ongoing row exposes the failings of applying a "one size fits all" policy to a complex area of medicine, and the time has come for change.

ID high risk groups?

Baum, an early pioneer of breast screening said he became so sickened by the refusal of health officials to update patient information leaflets with data on potential benefits and harms that he resigned from the programme after 10 years.

He now has a proposal for a solution: "What I'm advocating is that instead of one-size-fits-all we should think of it in the same way we think of other screening approaches -- we should identify the high risk groups first."

Baum favours a "triage" system to divide women into high, middle and low-risk groups based on family history and lifestyle factors like alcohol consumption, weight, diet and exercise.

He says high-risk women -- those with a long family history of breast cancer -- should be offered genetic testing to find out if they have a gene mutation which predisposes them to the disease, while low-risk women should get advice on healthy eating, avoiding alcohol and minimising other risk factors.

Screening would then be reserved for those in the middle, where he thinks the benefit-risk balance makes most sense.

"At the beginning I was convinced enough (about breast cancer screening) to actively involve myself in setting it up, but as the numbers change, the mind has to change," said Baum. "This is the whole point of science. As the evidence changes, you must change your mind.

Does this affect South African women?

Accoridng to Professor Justus Apffelstaedt (Associate Professor of Surgery,  University of Stellenbosch;  Head of the Breast Clinic at Tygerberg Hospital), he beleives that "Gotzsche is stirring controversy with ill-executed research". 

"I fully agree with Michael Baum, but I have seen only a minuscule minority of women losing weight, refraining from alcohol and exercising vigorously to reduce their breast cancer risk, never mind the heart disease risk, colon cancer risk etc.

"The reality is, that except for the decrease in the use of hormonal replacement therapy, other risk factors such as the increase of obesity are on the increase. These are politically very difficult to use to select women for screening mammography, " he said.

He added that hypothetically speaking, it would be like if a woman goes into a screening centre and is asked: Do you drink? If not, you won’t get a mammogram. Or, you have five kids, so you don’t need one or you are overweight and therefore you will get a mammogram. 

"Early in my practice, a woman came for screening and was assessed with the sophisticated computerised risk assessment. She had a substantially lower risk than the average population; to be exact, it was a third of the normal risk.

"She then had a mammogram and – Bingo! there was the cancer.  So ... currently available risk assessment tools are too crude and awkward to apply as a selection tool for screening mammography with the very small exception of women who are BRCA mutation carriers and have a very high risk of breast cancer; we already filter these out with genetic testing.

"This group is, however, less than one in a hundred women. The problem remains to accurately select the group of women, who are at moderately increased risk of breast cancer."

Apffelstaedt concluded that "Unless a superior method of breast cancer screening is found or moderately increased risk patients can be filtered out by other means than stratifying according to politically unacceptable criteria, we should proceed with mammography."

Sources: Reuters, Professor Justus Apffelstaedt (Associate Professor of Surgery,  University of Stellenbosch;  Head of the Breast Clinic at Tygerberg Hospital) 

(Health24, April 2010)

 

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Breast cancer expert

Dr Gudgeon qualified in Birmingham, England, in 1968. She has more than 40 years experience in oncology, and in 1994 she founded her practice, Cape Breast Care, where she treats benign and malignant breast cancers. Dr Boeddinghaus obtained her qualification at UCT Medical School in 1994 and her MRCP in London in 1998. She has worked extensively in the field of oncology and has a special interest in the hormonal management of breast cancer. She now works with Dr Gudgeon at Cape Breast Care. Read more.

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