Twenty five year follow-up for breast cancer incidence and mortality of the Canadian National Breast Screening Study: randomised screening trial
BMJ 2014; 348 doi: https://doi.org/10.1136/bmj.g366 (Published 11 February 2014) Cite this as: BMJ 2014;348:g366
All rapid responses
Rapid responses are electronic comments to the editor. They enable our users to debate issues raised in articles published on bmj.com. A rapid response is first posted online. If you need the URL (web address) of an individual response, simply click on the response headline and copy the URL from the browser window. A proportion of responses will, after editing, be published online and in the print journal as letters, which are indexed in PubMed. Rapid responses are not indexed in PubMed and they are not journal articles. The BMJ reserves the right to remove responses which are being wilfully misrepresented as published articles or when it is brought to our attention that a response spreads misinformation.
From March 2022, the word limit for rapid responses will be 600 words not including references and author details. We will no longer post responses that exceed this limit.
The word limit for letters selected from posted responses remains 300 words.
The real tragedy is not that an article was reported which describes the results of a deeply flawed trial - physicians can determine for themselves how to interpret these results. The problem is that major media markets picked up the trial are reported the results as a valid challenge to the routine use of mammography. It is not. Most dramatically the New York Times (The Paper of Record) reported a completely unbalanced view of the study, ignored larger, better studies and left the reader with the impression that mammography just does not matter. This is the height of irresponsibility. The BMJ simply reported the results of a trial. It does make one wonder, however, if other journals demurred, realizing that this paper advertises much more than it sells.
Competing interests: No competing interests
Computer scientists have an excellent term for nonsense output when input is faulty--GIGO, garbage in, garbage out. This is, unfortunately, what characterizes the Canadian breast cancer screening trial. The cascade of errors in this trial has been eloquently described by others--from substandard mammography (even for the time), inadequate training of mammography interpreters, poor followup of mammographically detected abnormalities, and nonrandomized allocation of women entered into the trial. High numbers of participants and long-term followup of a poorly executed trial cannot be expected to address the deficiencies present at the outset of this trial.
One need only look at Table 1 to realize that something was seriously awry. In no way do the numbers reflect expected (and observed) results when screening is performed properly. Not only was the average size of the cancers detected by screening nearly the same as that of palpable cancers in the control group but there is no evidence of a decrease in average tumor size over time as one would expect for incident vs. prevalent cancers.
Although the authors claim that randomization was blinded, the significant excess of breast cancers in the screening arm at year 1 coupled with the relatively large average size of the cancers does not favor an explanation of overdiagnosis. And what happened to overdiagnosis in the subsequent 15 years when the number of cancers detected in the screening arm was equal to or less than in the control arm? Overdiagnosis unquestionably occurs in breast cancer screening with mammography but in a study focused on invasive cancers with average tumor sizes of 1.9 cm, the plausibility of significant numbers of 'overdiagnosed' lesions has to be seriously questioned.
The primary lesson we should learn from the Canadian trial is that screening mammography done poorly does not work. Basing decisions about screening on this trial--the only outlier among eight other randomized controlled trials--is tantamount to having the asylum run by the inmates.
Competing interests: No competing interests
Dear Editors,
The recent study by Miller et al. (2014) claims to show that annual mammography screening does not reduce breast cancer mortality. An accompanying editorial concludes that the evidence does not support screening women under 60 (Kalager, Adami, and Bretthauer 2014).
Both conclusions are wrong. In fact, this study’s best estimate is that mammography reduced breast cancer mortality by 11.5 deaths per 100,000 women screened. Based on the 95% confidence interval on the effect, their results are consistent with it being cost-effective to spend $12,000 per person on such a screening program.
The reduction in 25-year cumulative mortality from breast cancer by 11.5 deaths per 100,000 people screened can be found simply by comparing deaths in the treatment group (500 out of 44925, or 1113.0 per 100,000) to those in the control group (505 out of 44910, or 1124.5 per 100,000). Another way of presenting this result is that they find a hazard ratio of 0.99: the death rate of treatment divided by death rate of controls.
Why then do Miller et al. claim that annual mammography screening does not reduce mortality from breast cancer? Because the 95% confidence interval on the effect of screening includes the possibility that it has no effect: the 95% confidence interval on the hazard ratio ranges from 0.88 to 1.12. (A hazard ratio of 1 means no difference in deaths between the two groups.) Nonetheless, the point estimate is that annual screening saves lives, even while the 95% confidence interval indicates substantial uncertainty.
Given this uncertainty, is continued annual mammography screening worth continuing? Put another way, is it cost-effective? A very rough calculation shows that it might well be. (A full cost-effectiveness calculation is certainly worth doing). Suppose the value per life saved was set at $9.1 million (the value used by the U.S. federal government in 2013.) Then, a mammography screening program for 100,000 people that reduced 11.5 deaths—the point estimate in Miller et al. 2014— has a benefit from life saved of $104.7 million. Thus, a screening program with a cost $1047 per person would be cost-effective. Moreover, the 95% confidence interval from Miller et al. also consistent with a reduction of 135 deaths per 100,000 (i.e. a hazard ratio of 0.88). This would entail a benefit from life saved of $1.23 billion, and justify a program cost of $12,300 per person.
While Miller et al. could not reject the hypothesis that annual mammography screening had no effect, they can also not reject the hypothesis that screening saves 135 lives per 100,000 screened, which would justify a screening program substantial costs. We still don’t know for sure—and there are other costs to consider, such as the risk of over treatment— but this study’s best estimate is that annual mammography screening reduces breast cancer mortality.
References
Miller, A. B., C. Wall, C. J. Baines, P. Sun, T. To, and S. A. Narod. 2014. “Twenty Five Year Follow-up for Breast Cancer Incidence and Mortality of the Canadian National Breast Screening Study: Randomised Screening Trial.” BMJ 348: g366–g366. doi:10.1136/bmj.g366.
Kalager, M., H.-O. Adami, and M. Bretthauer. 2014. “Too Much Mammography.” BMJ 348: g1403–g1403. doi:10.1136/bmj.g1403.
Competing interests: No competing interests
Perhaps the authors of this study and the editors of this journal had not completed their training when the first publications relating to the study began to be published in the early 1990’s. At that time there was considerable criticism about the randomization of patients in the study. (1-5) The study was actually designed to evaluate the value of mammography in women ages 40 to 49. It was found that there was an excess of patients with advanced cancer found in women aged 40 -49 allocated to the mammography group. Tarone (5) noted that an excess of women with four or more positive nodes in the mammography group would not have arisen by chance if random allocation had been followed. It was subsequently revealed by nurses participating in the study that women with breast complaints were put in the mammography group.
In the current publication related to this study it is reported that 68 percent of the cancers in the mammography group were palpable. How is this possible? In addition there was little difference in the mean tumor size or in nodal involvement.
In my own practice the 681 invasive cancers detected on mammography average 6 mm in diameter compared to 13 mm for the 640 cancers detected by clinical examination. Nodal involvement in my patients is 19 percent if the cancer is detected on mammography compared to 39 percent if found on clinical examination. Eighty-five percent of my patients with cancers detected on mammography are treated with breast conservation compared to 77 percent of those detected on clinical examination. Ten year disease-free survival for my patients with mammographically detected cancers is 92 percent compared to 82 percent if the cancer was detected on clinical examination. My results are not exceptional.
The authors of the Canadian study, knowing full well that the randomization was flawed, are being unethical in publishing these results without mention of the early criticisms.
1. Mettlin CJ, Smart CR. The Canadian National Breast Screening Study. Cancer 1993; 72 (Suppl): 1461-1465.
2. Conseil d’Evaluation des Technologies de la Santes (CETS). Screening for breast cancer in women 40-49 years. Montreal: CETS; 1993.
3. Kopans DB, Feig SA. The Cannadian National Breast Screening Study: A critical review. Am J Roentgenol 1993; 161: 755-760.
4. Baines CJ. The Canandian National Breast Screening Study: A perspective on criticisms. Ann Intern Med 1994;,120:326-334.
5. Tarone RE. The excess of patients with advance cancer in young women screened with mammography in the Canadian National Breast Screening Study. Cancer 1995; 75: 997-1003.
Competing interests: No competing interests
Dear Editor,
It appears that the authors conclusions that annual mammography does not reduce mortality in women age 40-59 beyond that of physical examination or usual care oversteps the limitations of the study. The correct conclusion is that in the 1980s annual clinical breast examinations and training in self breast exam produced nearly equivalent breast cancer specific mortality rates compared to annual mammography screening coupled with annual clinical breast exams and training in self breast exams.
The reasons are the following:
1) All participants in the randomized clinical trial (RCT) had clinical breast exams and were taught breast self examinations at the beginning of the study. The women 40-49 years of age were thereafter randomized to mammography or usual care but the 50-59 year old women were randomized to mammography and annual physical examination or no mammography and annual physical examination. At no point in the RCT was there an arm without either initial clinical breast exam, training in self breast exam, or usual care.
2) A relatively small number of cancers, 32%, were found by mammography alone in the mammography arm of the study. The rest were palpable and were found by either the patient or at the annual physical exam.
3) The mean tumor sizes found in the control arm are not what would be expected in a study with a nonintervention control arm. In our study of mammography detected breast cancer among women age 40-49 we found mean size of mammography detected tumors to be 1.8 cm and the patient/physician detected (palpable) tumor mean size was 3 cm. (1)
4) There were 10% fewer deaths from breast cancer among the mammography detected tumors (19.8%) compared to the palpable tumors (30.4%) in the mammography arm of the study indicating an advantage from detection of breast cancer at an earlier non-palpable stage.
The author’s assertions of overdiagnosis are hard to accept at face value when even the patients with the smallest non-palpable tumors found in the mammography screening arm had a 20% death rate from breast cancer. In our study of breast cancer mortality and treatment by detection method with cases from 1990 to 2008 tracked by our institutional cohort registry the observed death rate from breast cancer among mammography detected cancers was 4% and among patient or physician detected breast cancers was 11%.(1) All breast cancer discovered in this RCT had a hefty breast cancer death rate of 20 to 33% presenting a situation in which it does not appear any of the breast cancer discovered was not going to present harm to the patient during her lifetime. The high rate of breast cancer specific mortality seen in all arms of the study may be due to treatment that has currently been improved upon but was standard of care in the 1980s.
It is not clear if the technology in use in the 1980s when this particular RCT was conducted are comparable to current technology and is particularly questionable given the small difference in mean tumor size observed between arms. Given the small differences in size observed it is doubtful this study has relevance to current technology and the capacity of mammography to be superior to palpation as a method to detect breast cancer at an earlier more treatable stage.
Reference
1) Malmgren JA, Parikh J, Atwood MK, Kaplan HG. Impact of mammography detection on the course of breast cancer in women aged 40-49 years. Radiology 2012;262(3):797-806.
Competing interests: No competing interests
Dear Editor,
The Canadian National Breast Screening Study has serious sources of distorsion (methodological issues) that have been already mentioned in previous responses to this article. In addition, we have some concerns regarding how the authors presented their findings that can lead to misleading decisions regarding screening.
We wondered why the authors did not stratify the analysis according to age groups. Evidence indicates that there is more harm and less gain for women aged 40-49 years in terms of the number of deaths prevented. Another reason to stratify according to age groups is that they were not comparable in terms of the control arm. Younger women (40-49 years) allocated to he control arm were told to remain under the care of their family doctor whereas older women (50-59 years) were offered annual physical examinations.
The Independent UK Panel on Breast Cancer Screening stated that although there is no single optimum way to estimate overdiagnosis the two most useful estimates are: from the population perspective, the proportion of all cancers ever diagnosed in women invited to screening that are overdiagnosed and from the perspective of a woman invited to screening, the probability that a cancer diagnosed during the screening period represents overdiagnosis.
The authors missed the opportunity to estimate overdiagnosis using the population perspective. That is, the excess of cancer as the proportion of cancers diagnosed over whole follow-up period in women invited for screening (Table 1).
They did not clarify how they estimated overdiagnosis, there is no explanation why they measured the excess cancer cases at 15 years -instead of 25 years of follow-up- and why they considered as the denominator 484 screening detected cancers -not reproducible data- .
References
1. Independent UK Panel on Breast Cancer Screening. The benefits and harms of breast cancer screening: an independent review. Lancet. 2012;380.1778-86.
Competing interests: No competing interests
Dr. Daniel B. Kopans' claim of lack of proper randomization in the trial by Miller, et al., 2014 [1] in his response on 12-Feb-2014 is based on a paper from 1995 [2] which found more participants in the screening arm had invasive breast cancer at the start of the longterm study by Miller, et al., 2014 [1]. This bias, Kopans countered, would result in "more early deaths among the screened women than the control women", diminishing the value of mammography. Other researchers, however, were unable to verify the group allocation lapse in the work of Miller and collaborators, a specific criticism promulgated frequently by Kopans and others [3,4].
Moreover, Miller, et al., 2014, explained in their most recent study paper that "if" there was a bias in randomization at the start of the trial, "the bias would only impact on the results from breast cancers diagnosed during the first round of screening" [1] as these existing excess cancers would have been detected upon the initial or following screening, in a study that went through many screenings and lasted for over twenty years and, therefore, would not affect the results found in their latest follow-up study. Furthermore, Miller, et al., 2014 pointed out that even after this excess of incurable breast cancer is removed from the mortality analysis of the screened participants "the data do not support a benefit for mammography screening" [1].
Why didn't Kopans mention this crucial set of information in his vehement dismissal of the trial by Miller, et al., 2014 which he equates to a paper portraying a "suspect" analysis of results and "corrupted results"? Doesn't this omission indicate bias on Kopans' side, thus resulting in a display of "corrupted results" and a "suspect" commentary? It can hardly be explained by Kopans' failure to read the actual study of Miller and colleagues as he cites and refers to specific details from their paper.
Much of the criticism brought forward by Kopans had been addressed and refuted in earlier papers by Miller and colleagues [5,6] yet Kopans and others keep resorting to the same, or similar, misleading allegations.
In a prior paper of Kopans [7] he stated that the excess of breast cancer mortality, an outcome of the purported biased group allocation of individuals with invasive cancer upon trial commencement, was still apparent after ten years in the screened group of the longterm study lead by Dr. Anthony B. Miller. If this is the case it suggests screening with mammography fails to effectively detect incurable lethal cancers (but rather finds many non-cancers via overdiagnosis).
In his response, Kopans attributes the "extremely low" breast cancer detection percentage of 32%, reported in the latest analysis by the Miller group, to poor administration of the mammogram procedure, leading to missed cancers. Instead, Kopans claims, "at least two thirds of the cancers should be detected by mammography alone" based on a 2010 study he cites. However, another investigation, using data derived during the 1990s thus more consistent with the study time-frame of the Canadian trial, denoted a cancer detection of 29% by mammography alone [8].
Kopans describes in his critique how the low detection of breast cancer in the study by Miller, et al., 2014 is a sign of "the poor quality of the mammography" implementation of that study, pertaining to allegedly the use of "second hand" old mammographic equipment and the improper application of the procedure although the Miller team denoted that "the screening examination was properly conducted". The newer mammogram technology of today leads to a higher detection rate [9,10] but also elevates the magnitude of overdiagnosis, increasing the serious unnecessary harm to women via overtreatment. The extent of overdiagnosis from mammography was shown to be both large and significant [11-13].
Most of the mammogram studies showing a significant benefit are also older, having used old mammogram machines. Does the old technology argument only carry validity and relevance to adherents of mammography when a study doesn't find any meaningful value with screening? Some people would call that bias.
Kopans belittles an alleged previous notion of the study's [1] "principal investigator" -that is, the squeezing motion of the mammogram procedure can promote the influx and growth of cancer cells, leading to early deaths- as "nonsense" and a "completely unsupportable theory" with "no scientific basis". Yet, robust scientific data, published in prestigious medical journals, have lent meaningful support to the concept [14-16].
Kopans declared that he has no competing interests in his response comment but he is one of the principal developers of breast tomosynthesis, a digital form of mammography, and an inventor and patent holder (U.S. Patent No. 7,356,113) of a commercial digital breast tomosynthesis system [17,18]. Kopans also has not declared competing interests in other studies he co-authored promoting the value of his digital breast tomosynthesis system [19,20].
In my own personal, rather exhaustive, investigation of the value of mammography I have encountered numerous instances of omission, denial, derision, and obfuscation of genuinely relevant scientific data by the supporters of screening with mammography, shifting the "evidence" artificially in favor of the procedure. As a result, the general public and particularly women who decide to subject themselves to mammography, unfortunately, have been hampered from making an "informed choice" about this controversial test.
References:
1. Miller AB, Wall C, Baines CJ, Sun P, To T, Narod SA, "Twenty five year follow-up for breast cancer incidence and mortality of the Canadian National Breast Screening Study: randomised screening trial", BMJ. 2014 Feb 11;348:g366. doi: 10.1136/bmj.g366.
2. Tarone RE, "The excess of patients with advanced breast cancer in young women screened with mammography in the Canadian National Breast Screening Study", Cancer. 1995 Feb 15;75(4):997-1003.
3. Cohen MM, Kaufert PA, MacWilliam L, Tate RB, "Using an alternative data source to examine randomization in the Canadian National Breast Screening Study", J Clin Epidemiol. 1996 Sep;49(9):1039-44.
4. Bailar JC 3rd, MacMahon B, "Randomization in the Canadian National Breast Screening Study: a review for evidence of subversion", CMAJ. 1997 Jan 15;156(2):193-9.
5. Baines CJ, "The Canadian National Breast Screening Study: a perspective on criticisms", Ann Intern Med. 1994 Feb 15;120(4):326-34.
6. Miller AB, To T, Baines CJ, Wall C, "Canadian National Breast Screening Study-2: 13-year results of a randomized trial in women aged 50-59 years", J Natl Cancer Inst. 2000 Sep 20;92(18):1490-9.
7. Kopans DB, "Canadian National Breast Screening Study", Lancet. 1997 Sep 13;350(9080):810.
8. Sener SF, Winchester DJ, Winchester DP, Kurek R, Motykie G, Martz CH, Rabbitt S, "Spectrum of mammographically detected breast cancers", Am Surg. 1999 Aug;65(8):731-5; discussion 735-6.
9. Hambly NM, McNicholas MM, Phelan N, Hargaden GC, O'Doherty A, Flanagan FL, “Comparison of digital mammography and screen-film mammography in breast cancer screening: a review in the Irish breast screening program”, AJR Am J Roentgenol. 2009 Oct;193(4):1010-8.
10. Nederend J, Duijm LE, Louwman MW, Groenewoud JH, Donkers-van Rossum AB, Voogd AC, "Impact of transition from analog screening mammography to digital screening mammography on screening outcome in The Netherlands: a population-based study", Ann Oncol. 2012 Dec;23(12):3098-103. doi: 10.1093/annonc/mds146. Epub 2012 Jun 27.
11. Jørgensen KJ, Zahl PH, Gøtzsche PC, “Overdiagnosis in organised mammography screening in Denmark. A comparative study”, BMC Womens Health. 2009 Dec 22;9:36
12. Gøtzsche PC, Nielsen M, “Screening for breast cancer with mammography.”, Cochrane Database Syst Rev. 2011 Jan 19;(1):CD001877.
13. Bleyer A, Welch HG, "Effect of three decades of screening mammography on breast-cancer incidence", N Engl J Med. 2012 Nov 22;367(21):1998-2005.
14. van Netten JP, Mogentale T, Smith MJ, Fletcher C, Coy P, “Physical trauma and breast cancer”, Lancet. 1994 Apr 16;343(8903):978-9.
15. van Netten JP, Cann SA, Glover DW, "Mammographic compression: a force to be reckoned with", Br J Cancer. 1999 Dec;81(8):1426.
16. Abramovitch R, Marikovsky M, Meir G, Neeman M, "Stimulation of tumour growth by wound-derived growth factors", Br J Cancer. 1999 Mar;79(9-10):1392-8.
17. Chan HP, Wei J, Sahiner B, Rafferty EA, Wu T, Roubidoux MA, Moore RH, Kopans DB, Hadjiiski LM, Helvie MA, "Computer-aided detection system for breast masses on digital tomosynthesis mammograms: preliminary experience", Radiology. 2005 Dec;237(3):1075-80. Epub 2005 Oct 19.
18. Acciavatti RJ, Maidment AD, "Oblique reconstructions in tomosynthesis. II. Super-resolution", Med Phys. 2013 Nov;40(11):111912. doi: 10.1118/1.4819942.
19. Chan HP, Wei J, Zhang Y, Helvie MA, Moore RH, Sahiner B, Hadjiiski L, Kopans DB, "Computer-aided detection of masses in digital tomosynthesis mammography: comparison of three approaches", Med Phys. 2008 Sep;35(9):4087-95.
20. Chan HP, Wei J, Sahiner B, Rafferty EA, Wu T, Roubidoux MA, Moore RH, Kopans DB, Hadjiiski LM, Helvie MA, "Computer-aided detection system for breast masses on digital tomosynthesis mammograms: preliminary experience", Radiology. 2005 Dec;237(3):1075-80. Epub 2005 Oct 19.
Competing interests: Author of the (e)book "The Mammogram Myth"
The recent publication by Miller et al. [1] indicating no mortality benefits from mammography as part of the Canadian National Breast Screening Study is fraught with bias and the conclusions deeply suspect.
The study ignores pre-invasive cancers which have a high survival rate and are often detectable by mammography. It is reasonable to assume that if they had been included in the analysis then the mammography arm of the trial would have demonstrated higher survival rates than those reported. It is not safe to assume that all pre-invasive cancers are indolent (ie. that they would never go on to harm the patient), especially since the standard model of malignant tumour growth has invasive cancers first developing through a pre-invasive stage.
The study’s results contradict the authors’ conclusion that mammography is not assisting in saving women’s lives. The section of the Results titled “Breast cancer survival” indicates that “The 25 year survival was 70.6% for women with breast cancer detected in the mammography arm and 62.8% for women with cancers diagnosed in the control arm” which the authors demonstrate to be a statistically significant difference. This demonstrates a real benefit to women surviving breast cancer thanks to receiving mammographic screening. Had pre-invasive cancers been included in this study the difference in 25 year survival is liable to have been even larger. Concluding that mammographic screening provides no benefit with respect to saving women’s lives based on the analysis presented [1] is unfounded and dangerous.
[1] A. B. Miller, C. Wall, C. J. Baines, P. Sun, T. To, S. A. Narod, “Twenty five year follow-up for breast cancer incidence and mortality of the Canadian National Breast Screening Study: randomised screening trial,” British Medical Journal, 2014;348:g366.
Competing interests: No competing interests
Dear Sir/madam,
I note the above recent research paper with interest. In particular I wish to highlight a sentence in the conclusion and policy end paragraph:
"Nevertheless, education, early diagnosis, and excellent clinical care should continue to be provided to women to ensure that as many breast tumours as possible are diagnosed at or less than 2 cm."
I am a gynaecologist in private practice in Hong Kong. My sister, age 49, was diagnosed with breast cancer in the UK on the basis of a mammogram. It was 5 cms. When I asked her had she felt it, she said no, and that no-one had ever advised her to check her breasts. My sister was very lucky to be node negative, but after chemo and a local excision she did need a mastectomy. She received excellent care in the NHS. However had she been doing monthly breast self-examination I believe she would have picked up her “lump” when it was below 2 cms--perhaps 6 months – 1 year before--and she would not have needed the mastectomy.
Regular gynaecological check-ups of women in the UK is limited to a pap smear by a practice nurse every 2 years. I don’t think a bimanual examination to check for adnexal masses is ever done as a screening strategy for ovarian masses in the general practitioners offices. I don’t think a breast examination or advice to do breast self-examination is “routine”. I have asked my British clients here about whether they were ever advised to do, or taught how to do a breast self-examination in the UK, and 50% said no.
I think treatment of women’s cancers can be improved by earlier detection. Not by bumping up mammography numbers, clearly, given this Canadian study. But by improving screening strategy at the general practitioners offices.
Yours faithfully,
Sally Ferguson
Competing interests: No competing interests
Re: Twenty five year follow-up for breast cancer incidence and mortality of the Canadian National Breast Screening Study: randomised screening trial
In the conclusions and policy implications of the results of the study, the authors stated that in technically advanced countries “the rationale for screening by mammography should be urgently reassessed by policy makers”. Two weeks ago the Swiss Medical Board (SMB), an official expert panel created by the Swiss Medical Society, the Cantonal Health Authorities and by the Swiss Academy of Medical Sciences, has released a report on mammography screening that has no precedent in any other country. The conclusions of the report (1) have lead to the following recommendations:
a. It is not recommended that systematic mammography screening programs be introduced.
b. A time limit is to be set on existing systematic mammography screening programs.
c. All forms of mammography screening are to be evaluated with regard to quality.
d. Likewise, for all forms of mammography screening, a previous thorough medical evaluation and a comprehensible clarification with presentation of the desirable and undesirable effects are recommended.
As expected the report has raised a number of critiques in particular by those who lead public screening programs, the Swiss Cancer League and by the Federal Office of Public Health. The study by Miller et al. was published at the right time to strengthen and further endorse the SMB recommendations.
1. http://www.medical-board.ch/fileadmin/docs/public/mb/Fachberichte/2013-12- 15_Rapport_Mammographie_Final_rev.pdf
Competing interests: No competing interests