Re: Overdiagnosis in mammography screening: a 45 year journey from shadowy idea to acknowledged reality
I agree with Gøtzsche and Jørgensen that science must be about finding the most reliable facts not reaching consensus. I would like to clarify that I did not call for an evidence consensus. I called for an agreement about methods and process which would allow us to move forward with evidence.
To move forward, we urgently need agreement between experts on which study types can reliably measure and monitor overdiagnosis in contemporary screening programs (1). Despite compelling evidence presented by Carter et al about the biases of some study types (1), agreement on such a hierarchy of study designs appears to be a long way off. Furthermore, we need agreement between experts about how to express and calculate overdiagnosis. As outlined by Marmot et al (2), and earlier by De Gelder et al (3), there are many ways to do this, with varying numerators and, especially, denominators. We also need agreement about how to identify and remove conflicts of interests from influencing panels and committees reviewing evidence about mammography screening (4).
The entrenched disagreement between experts about how often overdiagnosis occurs is important to resolve because its continuation impedes policy development and makes it easy for screening services to continue to promote breast screening with persuasive and uninformative campaigns, while providing buried, conflicting or no information about overdiagnosis (5). As Celebuzki commented “Women deserve to know the truth, but wherever mammography screening is promoted they know zero about overdiagnosis”. With agreement on methods and process, it should be possible to appraise and synthesise the evidence about how often overdiagnosis occurs and develop evidence-based information for women, doctors and policy makers that will not be immediately challenged by one group of experts or another.
As Thornton describes, the history of mammographic screening is long and complex. There have been, and still are, many players, and the current problems will not be solved by leaving out the political aspects. A quick glance at the continuing celebrity endorsement of breast screening shows just how much of socio-cultural phenomenon it is (6). Experts are social and political beings too. Moving things forward will inevitably be a social process as much as a scientific one.
Zorzi makes the important point that many women around the world are screened outside of organised screening programs, with strong social and political support for breast screening internationally. One only has to look at the uptake of Pink Illumination to see the extent of international political support (7). I am increasingly concerned for women in developing regions of the world, who may be harmed by uncritical promotion of breast screening, based on developed country policies, without adequate information (8).
Gøtzsche and Jørgensen also elaborated on my statement that advanced cancer rates remained stable or have declined only modestly. They are correct that the paper by Biesheuvel et al (9) is not relevant and should have only been cited in relation to the first half of the same sentence; I apologise for this error. The other studies report small declines in advanced cancer rates (10-14). I agree with them that these small declines cannot be causally attributed to screening with any confidence and cannot be considered evidence of benefit from screening. However, I find it impressive that the declines are, at most, small (irrespective of their cause). Taken together with the much larger increases in early cancer rates, repeatedly observed, following screening introduction, these small (or zero) declines in advanced cancer incidence strongly suggest overdiagnosis. Overdiagnosis was the focus of my article, not the benefit of screening.
1. Carter JL, Coletti RJ, Harris RP. Quantifying and monitoring overdiagnosis in cancer screening: a systematic review of methods. BMJ. 2015;350:g7773.
2. Marmot MG, Altman DG, Cameron DA, Dewar JA, Thompson SG, Wilcox M. The benefits and harms of breast cancer screening: an independent review. Br J Cancer. 2013;108(11):2205-40.
3. De Gelder R, Heijnsdijk EA, van Ravesteyn NT, Fracheboud J, Draisma G, de Koning HJ. Interpreting overdiagnosis estimates in population-based mammography screening. Epidemiologic reviews. 2011;33(1):111-21.
4. Moynihan RN, Cooke GP, Doust JA, Bero L, Hill S, Glasziou P. Expanding disease definitions in guidelines and expert panel ties to industry: a cross-sectional study of common conditions in the United States. PLoS Med. 2013;10: e1001500. doi: 10.1371/journal.pmed.1001500
5. http://newsroom.breastscreen.org.au/campaign-to-remind-women-to-screen-f...
6. http://www.nydailynews.com/entertainment/tv/amy-robach-good-morning-amer...
7. http://www.pinkribbon.org/?tabid=374
8. http://www.prnewswire.com/news-releases/breast-cancer-screening-mammogra...
9. Biesheuvel C, Barratt A, Howard K, Houssami N, Irwig L. Effects of study methods and biases on estimates of invasive breast cancer overdetection with mammography screening: a systematic review. The Lancet Oncology. 2007;8(12):1129-38.
10. Kalager M, Adami HO, Bretthauer M, et al. Overdiagnosis of invasive breast cancer due to mammography screening: results from the Norwegian screening program. Ann Intern Med 2012;156:491-9.
11. Hofvind S, Lee CI, Elmore JG. Stage-specific breast cancer incidence rates among participants and non-participants of a population-based mammographic screening program. Breast Cancer Res Treat 2012;135:291-9.
12. Bleyer A, Welch HG. Effect of three decades of screening mammography on breast-cancer incidence. N Engl J Med 2012;367:1998-2005.
13. Esserman L, Shieh Y, Thompson I. Rethinking screening for breast cancer and prostate cancer. JAMA 2009;302:1685-92.
14. De Glas NA, de Craen AJ, Bastiaannet E, et al. Effect of implementation of the mass breast cancer screening programme in older women in the Netherlands: population based study. BMJ 2014;349:g5410.
Rapid Response:
Re: Overdiagnosis in mammography screening: a 45 year journey from shadowy idea to acknowledged reality
I agree with Gøtzsche and Jørgensen that science must be about finding the most reliable facts not reaching consensus. I would like to clarify that I did not call for an evidence consensus. I called for an agreement about methods and process which would allow us to move forward with evidence.
To move forward, we urgently need agreement between experts on which study types can reliably measure and monitor overdiagnosis in contemporary screening programs (1). Despite compelling evidence presented by Carter et al about the biases of some study types (1), agreement on such a hierarchy of study designs appears to be a long way off. Furthermore, we need agreement between experts about how to express and calculate overdiagnosis. As outlined by Marmot et al (2), and earlier by De Gelder et al (3), there are many ways to do this, with varying numerators and, especially, denominators. We also need agreement about how to identify and remove conflicts of interests from influencing panels and committees reviewing evidence about mammography screening (4).
The entrenched disagreement between experts about how often overdiagnosis occurs is important to resolve because its continuation impedes policy development and makes it easy for screening services to continue to promote breast screening with persuasive and uninformative campaigns, while providing buried, conflicting or no information about overdiagnosis (5). As Celebuzki commented “Women deserve to know the truth, but wherever mammography screening is promoted they know zero about overdiagnosis”. With agreement on methods and process, it should be possible to appraise and synthesise the evidence about how often overdiagnosis occurs and develop evidence-based information for women, doctors and policy makers that will not be immediately challenged by one group of experts or another.
As Thornton describes, the history of mammographic screening is long and complex. There have been, and still are, many players, and the current problems will not be solved by leaving out the political aspects. A quick glance at the continuing celebrity endorsement of breast screening shows just how much of socio-cultural phenomenon it is (6). Experts are social and political beings too. Moving things forward will inevitably be a social process as much as a scientific one.
Zorzi makes the important point that many women around the world are screened outside of organised screening programs, with strong social and political support for breast screening internationally. One only has to look at the uptake of Pink Illumination to see the extent of international political support (7). I am increasingly concerned for women in developing regions of the world, who may be harmed by uncritical promotion of breast screening, based on developed country policies, without adequate information (8).
Gøtzsche and Jørgensen also elaborated on my statement that advanced cancer rates remained stable or have declined only modestly. They are correct that the paper by Biesheuvel et al (9) is not relevant and should have only been cited in relation to the first half of the same sentence; I apologise for this error. The other studies report small declines in advanced cancer rates (10-14). I agree with them that these small declines cannot be causally attributed to screening with any confidence and cannot be considered evidence of benefit from screening. However, I find it impressive that the declines are, at most, small (irrespective of their cause). Taken together with the much larger increases in early cancer rates, repeatedly observed, following screening introduction, these small (or zero) declines in advanced cancer incidence strongly suggest overdiagnosis. Overdiagnosis was the focus of my article, not the benefit of screening.
1. Carter JL, Coletti RJ, Harris RP. Quantifying and monitoring overdiagnosis in cancer screening: a systematic review of methods. BMJ. 2015;350:g7773.
2. Marmot MG, Altman DG, Cameron DA, Dewar JA, Thompson SG, Wilcox M. The benefits and harms of breast cancer screening: an independent review. Br J Cancer. 2013;108(11):2205-40.
3. De Gelder R, Heijnsdijk EA, van Ravesteyn NT, Fracheboud J, Draisma G, de Koning HJ. Interpreting overdiagnosis estimates in population-based mammography screening. Epidemiologic reviews. 2011;33(1):111-21.
4. Moynihan RN, Cooke GP, Doust JA, Bero L, Hill S, Glasziou P. Expanding disease definitions in guidelines and expert panel ties to industry: a cross-sectional study of common conditions in the United States. PLoS Med. 2013;10: e1001500. doi: 10.1371/journal.pmed.1001500
5. http://newsroom.breastscreen.org.au/campaign-to-remind-women-to-screen-f...
6. http://www.nydailynews.com/entertainment/tv/amy-robach-good-morning-amer...
7. http://www.pinkribbon.org/?tabid=374
8. http://www.prnewswire.com/news-releases/breast-cancer-screening-mammogra...
9. Biesheuvel C, Barratt A, Howard K, Houssami N, Irwig L. Effects of study methods and biases on estimates of invasive breast cancer overdetection with mammography screening: a systematic review. The Lancet Oncology. 2007;8(12):1129-38.
10. Kalager M, Adami HO, Bretthauer M, et al. Overdiagnosis of invasive breast cancer due to mammography screening: results from the Norwegian screening program. Ann Intern Med 2012;156:491-9.
11. Hofvind S, Lee CI, Elmore JG. Stage-specific breast cancer incidence rates among participants and non-participants of a population-based mammographic screening program. Breast Cancer Res Treat 2012;135:291-9.
12. Bleyer A, Welch HG. Effect of three decades of screening mammography on breast-cancer incidence. N Engl J Med 2012;367:1998-2005.
13. Esserman L, Shieh Y, Thompson I. Rethinking screening for breast cancer and prostate cancer. JAMA 2009;302:1685-92.
14. De Glas NA, de Craen AJ, Bastiaannet E, et al. Effect of implementation of the mass breast cancer screening programme in older women in the Netherlands: population based study. BMJ 2014;349:g5410.
Competing interests: No competing interests