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Screening for breast cancer – a short history of a big mistake

Back in 1998, in all good faith, I set up the service for the NHS Breast Screening Programme. Since then, I have become one of the most vociferous proponents for closing it down.

You probably want to know why I changed my mind so completely. At the heart of this is the question, how do you explain to a woman that she is ‘lucky’ that we caught breast cancer early yet she ends up having a mastectomy? And that she probably wouldn’t have needed treatment at all if we hadn’t called her in for a routine scan?

This is because mammograms can pick up a type of low-grade breast cancer called duct carcinoma in situ (DCIS), which is contained just in the milk ducts and has not spread into any of the surrounding breast tissue – about 60 per cent of DCIS cases are picked up by routine breast screening. Around half of these cancers turn out to be harmless. It is my view that too many healthy women are harmed by breast cancer screening. [1]

The story starts back in 1987 when the Forrest report was published just two weeks before a general election called by Margaret Thatcher. [2] This report was based on the review of all the available evidence that included two randomized trials plus three case control studies that predicted a 25 per cent relative risk reduction in breast cancer (cause specific) mortality favoring those who were invited to screening. It is noteworthy that little space was allocated to the potential harms of population based screening by mammography.

Not surprisingly, the government of the day, endorsed the recommendations and promised that, if re-elected, a comprehensive screening program involving women 50-65 who would be invited every three years for mammography, would be established. The NHS BSP was to be rolled out across the UK between 1988 and 1990. The service would be based on fixed screening units close to population of high density and mobile units for remote areas. All of these district units would feed into a select group of regional specialist centers in major hospitals who would be provided with additional facilities and manpower to handle the predicted surge in activity following the first round of screening. At that time I was professor of surgery at King’s College Hospital, a major teaching hospital in South East London caring for a socially deprived population.

We were also given the task of setting up the training centre for all the clinicians, radiologists and radiographers who would staff the other units serving the South East of England as the program was rolled out. We were given 12 months to finish the job that was completed on time and on budget in spite of continuing with our full time day jobs. I was proud of what we had achieved and in good faith, accepted the evidence available at that juncture. I threw myself into my leadership role in the NHSBSP and was rewarded by being offered a seat on the National committee running the show.

My love affair with the NHSBSP was short lived. Unlike most of the other members of the National Committee, I was directly involved in the day to day care of those women referred on to me as a consequence of the activities on the front line of the screening program. I found it very distressing to have to cope with otherwise well women who had popped into the screening unit in Butterfly Walk for a mammogram at the invitation of the Department of Health (DoH) and then found themselves labeled as a cancer victim. Worst of all were the unexpected high numbers diagnosed with duct carcinoma in situ (DCIS), a condition we rarely saw before screening began. Many of these cases were multifocal and ended up with a mastectomy, yet they may well have turned out to be harmless.

None of the DoH staffers or public health specialists on the National committee had to face the reality of these heart-breaking interviews. We were soon to learn that 20 per cent of the cancers diagnosed in Butterfly Walk were DCIS, yet before we opened our doors they amounted to less than one per cent of our practice. I drew short term comfort from this observation assuming that in the fullness of time this initial peak in the incidence of DCIS would be followed by a fall in the incidence of invasive breast cancer. I couldn’t have been more wrong.

Within a few more years others noted that the ‘interval cancer’ rates were far too high to achieve the predicted 25 per cent reduction in cause specific mortality. Interval cancers are those that appear as clinically detected lumps in the intervals between two invitations for screening examination. These tend to be the fast growing tumors that slip through the net. It rapidly became clear to me that we would never meet our targets and also there was no evidence for the predicted fall of invasive cancers following the mopping up of all these cases of DCIS. Furthermore, updated analysis of the evidence in the Forrest report together with the publication of new trial reports, persuaded independent authorities to lower the estimate for the reduction in breast cancer mortality in a population based screening program from 25 per cent to 15 per cent. [3] After six or seven years into the programme, by which time it had been rolled out to the four corners of the UK, including the Islands and Highlands of Scotland, it became obvious to me that the benefits of screening had been grossly overestimated whilst the downside had been virtually ignored. Yet the letter inviting women into the NHSBSP remained unchanged, optimistic, pretty pink and frankly coercive.

Things came to a head for me in December 1994. The deputy chief medical officer called an emergency meeting of the NHSBSP national steering committee in the week between Christmas and the New Year. The meeting was set up in order to come up with a strategy to protect the program in the face of the accumulation of adverse publications in the medical media. I argued passionately for a revision of the false promises in the leaflet that went out with the invitations so that the lay public would at least be able to make an informed choice, as in my mind it was a pretty close call to judge whether the benefits outweighed the harm. I was a lone voice at the table and the chairman summed up the opinion of the gathering as follows; “Professor Baum, if we include all this new information in the leaflets then the women are unlikely to attend and we will fail to reach our target of 70 per cent uptake.” To which I replied; “If that is indeed the view of this committee then I can no longer serve as I believe that women have the right to self determination, I hereby resign and intend to make my feelings felt by going public on the topic”. True to my word I published a long letter in the Lancet entitled Screening for breast cancer; time to think and stop, a few months later. [4]

Twenty five years after the NHSBP was launched, the Department of Health was at last forced to set up an independent review that considered the adverse effects of screening; and to accept that women should no longer be denied the facts in helping them to decide whether or not to accept the call that was to be rewritten as an invitation and not like a summons. [5] Following on from that a new information leaflet has been produced to accompany the invitation for screening that allows women to weigh up the balance of benefit versus harm so that she can reach an informed choice. Sadly this is not the case in the USA where women at all ages are coerced to attend for screening with the mantra, ‘catch it early, save your life and save your breast.’



  1. Gilbert Welch, H. Schwartz, L and Woloshin, S. What’s Making Us Sick Is an Epidemic of Diagnoses. The New York Times, January 2, 2007
  2. Forrest P, Breast Cancer Screening Report to the Health Ministers of England, Wales, Scotland and Northern Ireland, 1986
  3. U.S.Preventive Services Task Force. Screening for Breast Cancer: Recommendations and Rationale. Ann Intern Med 2002;137: 344-6.
  4. Baum M. Screening for breast cancer, time to think-and stop?  Lancet 1995; 346: 436-437.
  5. Independent UK Panel on Breast Cancer Screening. The benefits and harms of breast cancer screening: an independent review. Lancet 2012; 380:1778-86.








Professor Michael Baum
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