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Mammography screening ten years on: reflections on a decade since the 2001 review

posted on: 2011-10-27 13:05

Peter Gøtzsche, Director of the Nordic Cochrane Centre, is one of the authors of the landmark 2001 Cochrane systematic review ‘Screening for breast cancer with mammography’. Ten years on from first publication, he reflects on the review’s impact on healthcare policy and practice.

See also: Cochrane in the News report on planned review of UK breast cancer screening policy and the Cochrane Library Special Collection on breast cancer detection.

It created a lot of stir when we published our systematic review of mammography screening in The Lancet and in The Cochrane Library in October 2001. We showed that - because of substantial overdiagnosis – women who are screened have higher rates of aggressive treatment, including increased mastectomies. We also raised concerns about the reported benefits of screening based on our analysis of the methods used in several of the trials. In fact, we concluded in the Cochrane review that “The currently available reliable evidence has not shown a survival benefit of mass screening for breast cancer.”

Our finding of increased mastectomies has consistently been ignored by screening advocates for 10 years, and information from many cancer charities and governmental agencies continues to state the opposite – that screening decreases mastectomies - despite having no reliable data to support this claim. We recently confirmed that screening increases mastectomies, using data from both the Danish and Norwegian screening programmes (1, 2). We have also shown that many screening-detected cancers would have regressed spontaneously if they had been left alone, without treatment (3). By our estimates, the level of overdiagnosis in countries with organised screening programmes is about 50% (1).

Studies published in the last couple of years have failed to find an effect of screening in Europe, and have also failed to find a decrease in the occurrence of advanced cancers. When screening doesn’t decrease advanced cancers, it cannot work. We summarised the most important of this research in September 2011 (1).

There are likely three main reasons why screening is no longer effective. Adjuvant therapy, such as tamoxifen and chemotherapy, is highly effective (even when the cancer has metastasised), but was used very little in the old randomised trials. Increased breast cancer awareness has likely also been important, as women attend a doctor much earlier today if they have found anything unusual (1). Finally, diagnosis and treatment have been centralised in many countries, so that experts are available in all disciplines required for optimal processes.

Therefore, what was considered so controversial in 2001 is now increasingly being recognised to be true, even by people who advocated the introduction of screening in the first place. The tides are plainly turning for mammography screening, and it is now essential that women be provided with information that allows them to make an informed choice about mammographic screening, rather than being pushed toward mammography as routine, while being told it is an unambiguously beneficial test.

In 2009, we published an information leaflet on mammography screening in BMJ and on our website,, which volunteers have translated into 11 languages. We clearly need to update the leaflet, which starts thus: “It may be reasonable to attend for breast cancer screening with mammography, but it may also be reasonable not to attend, as screening has both benefits and harms.” It is getting more and more difficult to argue that it is reasonable to attend for breast screening.

Peter C. Gøtzsche
Director, The Nordic Cochrane Centre

October 2011


1 Jørgensen KJ, Keen JD, Gøtzsche PC. Is mammographic screening justifiable considering its substantial overdiagnosis rate and minor effect on mortality? Radiology 2011;260:621-6.

2 Suhrke P, Mæhlen J, Schlichting E, Jørgensen KJ, Gøtzsche PC, Zahl PH. Effect of mammography screening on surgical treatment for breast cancer in Norway: comparative analysis of cancer registry data. BMJ 2011; 343:d4692.

3 Zahl PH, Gøtzsche PC, Mæhlen J. Natural history of breast cancers detected in the Swedish mammography screening program; a cohort study. Lancet Oncol 2011;12 Oct. DOI:10.1016/S1470-2045(11)70250-9.


Re: Mammography screening ten years on: reflections on a ...

Response from Peter C Gøtzsche:

The Nordic Cochrane Centre is a research and information centre. It does not provide advice on treatment of individual patients. The General Medical Council of the United Kingdom ( has given the following advice to doctors in relation to e-mail consultations: There are problems in providing e-mail consultations because: (a) the doctor asked to discuss e-mail cases will not know the patient’s full details; (b) not all facts including the findings from a physical examination of the patient and the medical history, may be known; (c) there will be no provision for the monitoring of a case or follow up care.

Re: Mammography screening ten years on: reflections on a ...

I have been diagnosed with DCIS. Nuclear grade 2, 0.4 cm both estrogen and progesterone positive. I am 54 with no family history. I do have rheumatoid arthritis but have it under control with diet. I am scheduled for a lumpectomy and the doctor is suggesting tamoxifen and radiation therapy. I am considering tamoxifen but not radiation. I am afraid I am being over diagnosed. It is feeling of Catch 22. Is it beneficial to have ultrasound over excessive mammograms? I am so confused and don't know who to believe or who has my best interest at heart.




Relevance to women who have had cancer

I had early stage breast cancer last year (found by mammogram and ultrasound).  I've since had surgery and radiotherapy and I'm now taking Tamoxifen.  I'm 44 and have been screened every second year from 32 til 40 then every year since.  These mammograms were ordered by the surgeon who dealt with a lump I found at 32 that turned out not to be cancer.

Do the findings of this study apply equally to women who have had breast cancer? Are there studies that can help me decide whether to have annual mammograms from now on? My surgeon, oncologist and radiation oncologist all want me to and don't accept there is any radiation risk, but I'm not sure.  I certainly don't want more intervention because something is found by mammogram that left alone may resolve itself.


Re: Mammography screening ten years on: reflections on a ...

Thank you for this informative update. I am wondering if there are Cochrane Reports to support the statement that "Adjuvant therapy, such as tamoxifen and chemotherapy, is highly effective (even when the cancer has metastasised)." My understanding is that tamoxifen reduces recurrence rate, but does not increase overall survival; and chemotherapy for breast cancer reduces tumor size, but does not increase overall survival. Perhaps the difference is how effectiveness is defined?

Re: Mammography screening ten years on: reflections on a ...

Response from Peter:

Thank you for your comment. In the Mammography review (, the authors state the following, in the Discussion section: 'It has been suggested that resources be redirected to interventions with proven benefit in breast cancer (Baum 2000) or used for other purposes (NBCC 2002). For comparison, the benefit is 200 times greater when women with node-positive breast cancer are treated with tamoxifen since the average life extension is six months after 10 years (Early Breast C 1998).'1

Both tamoxifen and polychemotherapy are highly effective, and their effects are largely independent of nodal status and other tumour characteristics.2 Thus, the treatments work whether or nor the cancer is detected ‘early’.

1 Early Breast C 1998: Early Breast Cancer Trialists' Collaborative Group. Tamoxifen for early breast cancer: an overview of the randomised trials. The Lancet 1998;35:1451-67.

2 Early Breast Cancer Trialists’ Collaborative Group (EBCTCG). Effects of chemotherapy
and hormonal therapy for early breast cancer on recurrence and 15- year survival: an
overview of the randomised trials. Lancet. 2005; 365(9472): 1687–717.

Re: Mammography screening ten years on: reflections on a ...

I'm terribly grateful that we have some doctors prepared to tell us the truth and to fight for our right to make an informed decision about screening. Sadly, there are no advocates for informed consent in women's cancer screening in Australia - we only recently heard about over-diagnosis in breast screening from one doctor, who has been totally ignored - no other doctors have stepped forward to support her and the govt is silent. Our doctors are great at that...complete silence, except to push our screening programs.

We have a pap testing program that is excessive, harmful and more than a decade behind the evidence, the Dutch and Finnish programs demonstrate that very clearly. Yet the target that doctors must meet to collect a financial incentive has been raised to 70% of eligible patients and we're still telling women they need 26+ pap tests, including very young women. I can't understand what we're doing...and we have a senior doctor saying we shouldn't change the program and exclude young women until they've completed their research into the effectiveness of Gardasil - so women are IMO, little more than lab rats. There is no respect at all for informed consent - it's a joke.

We now know (thanks to the Dutch) that roughly 5% of women are HPV positive at age 30 and they should be offered a 5 yearly pap test, they have a small chance of benefiting, the rest (HPV negative) should be left alone and offered another 4 HPV primary tests (at 35, 40, 50 and 60) or they can test themselves with the Delphi Screener. There is no need to screen, worry and harm the masses, almost all of whom are HPV negative and not currently at risk from cc.

Over-detection and over-treatment affects most women at some stage in this country - 77% is the lifetime risk of referral (for a cancer with a 0.65% lifetime risk) Yet we're not supposed to question any of it...we're met with outrage on the very rare occasion someone challenges the program. This is not ethical cancer screening -IMO, this is not a program that operates for the benefit of women.

If not for people like Prof Baum, Angela Raffle, Gilbert Welch, Hazel Thornton, Margaret McCartney and Peter Gotzsche (none are Australian) I could not have made informed decisions about screening.

I'm currently being pressured to have bowel screening, a's a no-brainer apparently, but then they said the same thing about cervical and breast cancer screening.

I have declined routine breast exams, cervical screening, (as a low risk woman) breast cancer screening and refused the CA125 blood test for ovarian cancer (and I would also refuse routine pelvic exams, but they're not recommended here anymore)...and I'll keep refusing if I'm not satisfied. I know some doctors hate informed patients...and I'm probably labeled "difficult" even though I'm always polite...but as soon as you challenge some doctors they become prickly, abrupt and impatient. (and even rude) BUT, I believe we have to be very careful handing our asymptomatic bodies over for  can lead to some very nasty places.   


Re: Mammography screening ten years on: reflections on a ...

I still don't get what we're supposed to do instead of mammogram.  I know there is overdiagnosis [esp with dcis]. But if we wait till it's metastasized to find it, sure chemo can help, but we will die from the cancer. So, what's the answer?

Re: Mammography screening ten years on: reflections on a ...

It is more important to decrease the risk of getting cancer than to find cancer a few months earlier by screening. Screening increases the risk of becoming a breast cancer patient by about 50%, which means, as first stated by Maryann Napoli from the US Center for Medical Consumers, that if we wish to reduce the incidence of breast cancer, there is nothing as effective as avoiding getting mammograms. It reduces the risk of becoming a breast cancer patient by one-third.

As I have already stated above, screening is no longer effective in reducing mortality from breast cancer. The Nordic Cochrane Centre has therefore updated our screening leaflet in January 2012 so that it now says that it no longer seems reasonable to attend for breast cancer screening. This leaflet exists in 13 languages and will also be translated into Chinese, Arabic and Urdu.

I also published a book in January that explains the issues in a language that I have been told lay people and other non-specialists can understand. See

Women should of course attend a doctor if they have noticed anything unusual in their breasts, e.g. during a shower. Regular self-examination, e.g. every month, cannot be recommended, however, see the Cochrane review on this, CD003373.

Re: Mammography screening ten years on: reflections on a ...

Well done sir.  This work has influenced and continues the influence the informed consent process in our community.  

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