Large increase in a Dutch woman's lifetime risk of developing breast cancer. Eur J Cancer 2008; 44: 1485-1487 // 19 Aug 2008

Correspondence

Well here goes and let's start by looking at the first paper after the editorial.[2]

In this, Paap and co-authors, describe a large increase in a Dutch woman's lifetime risk of developing breast cancer in the years that followed the introduction of population screening in 1989. They seem to dismiss the importance of the over-diagnosis of breast cancer as a result of screening, even though the timelines run in parallel and even though this phenomenon has been noted on every occasion that population screening has been introduced into a country. [3]

It is no longer possible to ignore this over-diagnosis that according to some calculations runs at about 50%. [4,5,6,7] Screening must now be considered as one of the commonest "causes" of breast cancer in society, equal in importance to nulliparity and alcohol abuse.

One simple way of reducing the incidence of breast cancer would be to concentrate screening on high risk women and leave the rest of our womenfolk alone. Like us men, who can coexist in blissful ignorance of their latent prostate cancers until dying of old age, women should be granted that lost privilege of co-existing with their latent (pseudo) cancers until running out of their allotted lifespan.

Professor Michael Baum

Professor Emeritus of Surgery & Visiting Professor of Medical Humanities, University College London, The Portland Hospital

Great Portland Street, London W1N 6AH, Tel. +44(0)20 7034 8890, Fax. +44(0)20 7034 8883, Michael@mbaum.freeserve.co.uk

References

[1] Smyth JF, An invitation to correspond with us! European J Cancer 2008:44:1482

[2] Paap E. Broeders MJM, van Schoor G, Otten JDM, Verbeek ALM, Large increase in a Dutch woman's lifetime risk of developing breast cancer; 2008; 44: 1485-1487

[3] Black WC, Welch HG. Advances in Diagnostic Imaging and Overestimations of Disease Prevalence and the Benefits of Therapy. 1993;NEJM 328:1237-43

[4] Nielsen, M., Thomsen, J. L., Primdahl, S., Dyreborg, U., & Andersen, J. A. Breast cancer and atypia among young and middle-aged women: a study of 110 medicolegal autopsies (1987) Br J Cancer 56, 814-819.

[5] Welch HG, Black WC. Using autopsy series to estimate the disease “Reservoir” for ductal carcinoma in situ of the breast : How much more breast cancer can we find? Ann Intern Med 1997; 12: 1023-8

[6] Vaidya, J. S., Vyas, J. J., Chinoy, R. F., Merchant, N., Sharma, O. P., & Mittra, I. Multicentricity of breast cancer: whole-organ analysis and clinical implications (1996) Br. J Cancer 74, 820-824.

[7] Gotzsche, P. C. & Nielsen, M. Screening for breast cancer with mammography (2006) Cochrane. Database. Syst. Rev. CD001877

Author Responds 

SIR - We would like to comment on Professor Baum's response to our paper on the increase in a Dutch woman's lifetime risk of developing breast cancer during the period of 1989-2003.[1] 

The main goal in mammographic screening is to prevent breast cancer death through a shift in diagnosing breast cancer at a curable earlier stage. This automatically puts overdiagnosis as an important unfavourable side effect of screening in the picture, especially e.g. through the increase of incidence of DCIS.[2]

The amount of overdiagnosis through screening will be most pronounced during the implementation period of service screening, because of the excess incidence due to the overrepresentation of prevalent screens with prevalent cancers. After the implementation period the increase in newly diagnosed breast cancer cases and the decrease in incidence at older ages will lead to a steady state.[2] 

In the Netherlands the implementation period was finished in 1996 for the age group 50-69 years, so it can be expected that the excess incidence in this age group was stable during the following years of our study period. The implementation of the age group 70-74 started in 1997 and was completed in 2001. The incidence in this age group showed a peak in 1999, where after a decrease in incidence was observed.[3]

Quantification of overdiagnosis is difficult and estimates vary widely in the literature. The influence of overdiagnosis cannot be ignored indeed, but it seems to be a minor phenomenon in breast cancer screening.[2,4] In the Netherlands, modelling showed a 3% overdiagnosis of the total incidence and 8% in the screen detected cancers in 2002.[2] Data from randomised controlled trials can be used to determine the extent of overdiagnosis.[5] An overall estimate of overdiagnosis of two of those trials was around 1% of all cases diagnosed in the screened populations.[6] Taking these estimates into account, overdiagnosis due to screening does not seem to have an important role in the increasing incidence of breast cancer.

Besides the possible negative effects of screening and the increased incidence during the screening years, the 26% decrease in mortality of breast cancer in the Netherlands in that period is also worth mentioning.[7] 

Ellen Paap MSc

Department of Epidemiology, Biostatistics and HTA (HP 133), University Medical Centre, St Radboud, PO Box 9101 6500 HBm, Nijmegen, The Netherlands.

References

[1]  Paap E, Broeders MJ, van SG, Otten JD, Verbeek AL. Large increase in a Dutch woman's lifetime risk of developing breast cancer. Eur J Cancer 2008 Jul,44(11), 1485-1487.

[2] de Koning HJ, Draisma G, Fracheboud J, de BA. Overdiagnosis and overtreatment of breast cancer: microsimulation modelling estimates based on observed screen and clinical data. Breast Cancer Res2006,8(1), 271-275.

[3] Otten JD, Broeders MJ, Fracheboud J, Otto SJ, de Koning HJ, Verbeek AL. Impressive time-related influence of the Dutch screening programme on breast cancer incidence and mortality, 1975-2006. Int J Cancer 2008 Oct 15,123(8), 1929-1934.

(4) Paci E, Duffy S. Overdiagnosis and overtreatment of breast cancer: overdiagnosis and overtreatment in service screening.Breast Cancer Res2005,7(6), 266-270.

[5] Moss S. Overdiagnosis and overtreatment of breast cancer: overdiagnosis in randomised controlled trials of breast cancer screening. Breast Cancer Res 2005,7(5), 230-234.

[6] Duffy SW, Agbaje O, Tabar L, et al. Overdiagnosis and overtreatment of breast cancer: estimates of overdiagnosis from two trials of mammographic screening for breast cancer. Breast Cancer Res 2005,7(6), 258-265.

[7]  NETB (National Evaluation Team for Breast cancer screening). National evaluation of mass screening for breast cancer in the Netherlands. Evaluation report XI (In Dutch with English summay). Rotterdam. 2005.