Archived Comments for:
Trends in incidence and detection of advanced breast cancer at biennial screening mammography in The Netherlands: a population based study
Quoted Dutch breast screening papers were seriously misleading
Peter Gøtzsche, Nordic Cochrane Centre
9 March 2012
The study by Nederend et al. (1) failed to find a decline in advanced breast cancer in the Netherlands during 12 years of breast screening. This finding agrees with other recent papers suggesting that screening is not likely to be effective today (2,3).
The paper is convincing, but when discussing previous work by Dutch colleagues, Nederend et al. overlook obvious flaws (3). They say that, "Otto et al. reported a 19.9% reduction in breast cancer mortality rate in 2001 as a result of routine mammography screening in the Netherlands" (1). I explained in a letter to the editor in the same journal (4) that Otto et al. failed to mention that a similar reduction had occurred in young women who had not been invited to screening. Furthermore, Otto et al. had cherry-picked countries when they argued that the mortality had declined in some countries that have screening. The same had happened in some countries that didn¿t have a national screening programme, e.g. in Austria, Germany and Switzerland. Other Dutch researchers mentioned that the use of adjuvant therapy had increased substantially in the same time period and that it was therefore not possible to separate the possible effect of screening from the effect of better treatment (5). One of these critics, Voogd, co-authored Nederend's paper, and it is therefore a bit surprising that Voogd accepted Otto's result at face value this time, which is clearly unwarranted.
Nederend et al. furthermore say that, "Fracheboud et al. initially found a significant decrease in the incidence rate of advanced disease in women who participated in the Dutch screening program" (1). The paper they quote (6) cannot sustain this claim (3). The Dutch programme did not reduce the incidence of cancers with metastases, but the researchers concealed this fact by splitting the cancers with metastases in two groups, above and below 2 cm in size. This makes no sense when all the cancers had metastasised, but what immediately catches the eye in their figure is a graph with metastasised cancers bigger than 2 cm that appears to go down over time. The split of the data is misused in the abstract, which only mentions the larger cancers and notes that their incidence declined significantly. When I added the data from the graphs, I found that there was no reduction in incidence of cancers with metastases, in fact the combined incidence was identical for the first year reported, 1989, and for the last year, 1997.
Fracheboud et al. concluded, "It is evident that breast cancer screening contributes to a reduction in advanced breast cancers and breast cancer mortality." This is not what their study showed, and there are no data on breast cancer mortality in their paper. The dishonesty continued in the discussion section: "It is important to realise that the initial increase does not signify overdiagnosis, but that it is the result of the necessary downstaging of breast cancer diagnoses, if screening will be effective." There was no downstaging to cancers that had not metastasised.
What Fracheboud's study really showed was that screening is ineffective in the Netherlands and that it leads to a huge amount of overdiagnosis (as the incidence of localised cancers doubled, with no sign of a decrease). But Fracheboud et al. wrote exactly the opposite of what they found on both counts.
1. Nederend J, Duijm LE, Voogd AC, Groenewoud JH, Jansen FH, Louwman MW. Trends in incidence and detection of advanced breast cancer at biennial screening mammography in The Netherlands: a population based study. Breast Cancer Res 2012 Jan 9;14(1):R10 [Epub ahead of print].
2. Jørgensen KJ, Keen JD, Gøtzsche PC. Is mammographic screening justifiable considering its substantial overdiagnosis rate and minor effect on mortality? Radiology 2011;260:621¿7.
6. Fracheboud J, Otto SJ, van Dijck JA, et al. Decreased rates of advanced breast cancer
due to mammography screening in the Netherlands. Br J Cancer 2004;91:861¿7.
Quoted Dutch breast screening papers were seriously misleading
9 March 2012
The study by Nederend et al. (1) failed to find a decline in advanced breast cancer in the Netherlands during 12 years of breast screening. This finding agrees with other recent papers suggesting that screening is not likely to be effective today (2,3).
The paper is convincing, but when discussing previous work by Dutch colleagues, Nederend et al. overlook obvious flaws (3). They say that, "Otto et al. reported a 19.9% reduction in breast cancer mortality rate in 2001 as a result of routine mammography screening in the Netherlands" (1). I explained in a letter to the editor in the same journal (4) that Otto et al. failed to mention that a similar reduction had occurred in young women who had not been invited to screening. Furthermore, Otto et al. had cherry-picked countries when they argued that the mortality had declined in some countries that have screening. The same had happened in some countries that didn¿t have a national screening programme, e.g. in Austria, Germany and Switzerland. Other Dutch researchers mentioned that the use of adjuvant therapy had increased substantially in the same time period and that it was therefore not possible to separate the possible effect of screening from the effect of better treatment (5). One of these critics, Voogd, co-authored Nederend's paper, and it is therefore a bit surprising that Voogd accepted Otto's result at face value this time, which is clearly unwarranted.
Nederend et al. furthermore say that, "Fracheboud et al. initially found a significant decrease in the incidence rate of advanced disease in women who participated in the Dutch screening program" (1). The paper they quote (6) cannot sustain this claim (3). The Dutch programme did not reduce the incidence of cancers with metastases, but the researchers concealed this fact by splitting the cancers with metastases in two groups, above and below 2 cm in size. This makes no sense when all the cancers had metastasised, but what immediately catches the eye in their figure is a graph with metastasised cancers bigger than 2 cm that appears to go down over time. The split of the data is misused in the abstract, which only mentions the larger cancers and notes that their incidence declined significantly. When I added the data from the graphs, I found that there was no reduction in incidence of cancers with metastases, in fact the combined incidence was identical for the first year reported, 1989, and for the last year, 1997.
Fracheboud et al. concluded, "It is evident that breast cancer screening contributes to a reduction in advanced breast cancers and breast cancer mortality." This is not what their study showed, and there are no data on breast cancer mortality in their paper. The dishonesty continued in the discussion section: "It is important to realise that the initial increase does not signify overdiagnosis, but that it is the result of the necessary downstaging of breast cancer diagnoses, if screening will be effective." There was no downstaging to cancers that had not metastasised.
What Fracheboud's study really showed was that screening is ineffective in the Netherlands and that it leads to a huge amount of overdiagnosis (as the incidence of localised cancers doubled, with no sign of a decrease). But Fracheboud et al. wrote exactly the opposite of what they found on both counts.
1. Nederend J, Duijm LE, Voogd AC, Groenewoud JH, Jansen FH, Louwman MW. Trends in incidence and detection of advanced breast cancer at biennial screening mammography in The Netherlands: a population based study. Breast Cancer Res 2012 Jan 9;14(1):R10 [Epub ahead of print].
2. Jørgensen KJ, Keen JD, Gøtzsche PC. Is mammographic screening justifiable considering its substantial overdiagnosis rate and minor effect on mortality? Radiology 2011;260:621¿7.
3. Gøtzsche PC. Mammography screening: truth, lies and controversy. London: Radcliffe Publishing; 2012.
4. Gøtzsche PC. Mortality reduction by breast- cancer screening. Lancet 2003;362:246.
5. Voogd AC, Coebergh JWW. Mortality reduction by breast-cancer screening. Lancet 2003;362:245¿6.
6. Fracheboud J, Otto SJ, van Dijck JA, et al. Decreased rates of advanced breast cancer
due to mammography screening in the Netherlands. Br J Cancer 2004;91:861¿7.
Competing interests
None