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Alternative Estimates for the Likelihood That a Woman With Screen-Detected Breast Cancer Has Had Her “Life Saved” by That Screening

Alternative Estimates for the Likelihood That a Woman With Screen-Detected Breast Cancer Has Had... We welcome the method by Welch and Frankel1 of estimating the probability (P) that a woman with a screen-detected cancer had her life saved by the screening program [P(life saved screen-detected cancer diagnosis)]. When using this model, the estimated probability ranges from 2.5% to 24.0%; for women aged 50 years, the estimated probability is 13%. We were intrigued by this number, since this probability previously has been estimated to be 4.8%.2 In his model, Keen2 used 2 parameters: (1) an estimate of the absolute risk reduction of breast cancer mortality with mammography screening and (2) the cumulative incidence of screen-detected cancers. We have applied Keen's model to Danish data. During 1997 through 2006, 3 Danish municipalities had organized mammography screening (Copenhagen, Funen, and Frederiksberg). We were able to obtain data referring to the Copenhagen municipality. The number of screen-detected cancers from the first to seventh round (April 4, 1991, to December 31, 2005) has been published.3 We have obtained the number of screen-detected cancers over 5 rounds of screening (a 10-year period, from April 26, 1993–May 31, 2003). From the municipality population registry4 we obtained the midperiod number of women aged 50 to 69 years living in the Copenhagen municipality from January 1, 1993, through December 31, 2002. Using these 2 numbers, we estimated the incidence of screen-detected cancers over a 10-year period to be 20 per 1000 women aged 50 to 69 years. Assuming an absolute risk reduction of 1 breast cancer death per 2000 screened women,5 we have reached a P(life saved screen-detected cancer diagnosis) of 2.5%. We acknowledge that Welch and Frankel1 have been more cautious in their assumptions than we have. In doing so, they have avoided underestimation of any mammography effect, which only strengthens their main argument: for a breast cancer survivor, the probability that her life was saved by screening is, at most, 24%. Beyond the issue of the assumptions, we believe that the main explanation for the difference between estimates of P(life saved screen-detected cancer diagnosis) lies in the choice of measure used to quantify risk. In Keen's model (that we replicated using Danish data), a 10-year cumulative incidence is used. In the model by Welch and Frankel, a 20-year probability is used. For similar populations, these 2 risk measures provide numbers that are very different in terms of magnitude. This magnitude difference can leave clinicians and patients confused. We would like to invite Welch and Frankel to comment on the advantages of using probabilities conditioned on age when communicating with patients. Back to top Article Information Correspondence: Dr Heleno, Research Unit and Section for General Practice, University of Copenhagen, Øster Farimagsgade 5, Entrance Q, First Floor, PO Box 2099, Copenhagen K 1014, Denmark (bruno.heleno@sund.ku.dk). Financial Disclosure: None reported. References 1. Welch HG, Frankel BA. Likelihood that a woman with screen-detected breast cancer has had her “life saved” by that screening. Arch Intern Med. 2011;171(22):2043-204622025097PubMedGoogle ScholarCrossref 2. Keen JD. Promoting screening mammography: insight or uptake? J Am Board Fam Med. 2010;23(6):775-78221057074PubMedGoogle ScholarCrossref 3. Utzon-Frank N, Vejborg I, von Euler-Chelpin M, Lynge E. Balancing sensitivity and specificity: sixteen year's of experience from the mammography screening programme in Copenhagen, Denmark. Cancer Epidemiol. 2011;35(5):393-39821239242PubMedGoogle ScholarCrossref 4. Københavns Kommune. Personbiler: Statistikbanken. http://www.statistikbanken.dk/statbank5a/SelectTable/Omrade0.asp?PLanguage=1. Accessed December 19, 2011 5. Gøtzsche PC, Nielsen M. Screening for breast cancer with mammography. Cochrane Database Syst Rev. 2011;(1):CD00187721249649PubMedGoogle Scholar http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Archives of Internal Medicine American Medical Association

Alternative Estimates for the Likelihood That a Woman With Screen-Detected Breast Cancer Has Had Her “Life Saved” by That Screening

Alternative Estimates for the Likelihood That a Woman With Screen-Detected Breast Cancer Has Had Her “Life Saved” by That Screening

Abstract

We welcome the method by Welch and Frankel1 of estimating the probability (P) that a woman with a screen-detected cancer had her life saved by the screening program [P(life saved screen-detected cancer diagnosis)]. When using this model, the estimated probability ranges from 2.5% to 24.0%; for women aged 50 years, the estimated probability is 13%. We were intrigued by this number, since this probability previously has been estimated to be 4.8%.2 In his model, Keen2 used 2 parameters: (1) an...
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Publisher
American Medical Association
Copyright
Copyright © 2012 American Medical Association. All Rights Reserved.
ISSN
0003-9926
eISSN
1538-3679
DOI
10.1001/archinternmed.2012.352
Publisher site
See Article on Publisher Site

Abstract

We welcome the method by Welch and Frankel1 of estimating the probability (P) that a woman with a screen-detected cancer had her life saved by the screening program [P(life saved screen-detected cancer diagnosis)]. When using this model, the estimated probability ranges from 2.5% to 24.0%; for women aged 50 years, the estimated probability is 13%. We were intrigued by this number, since this probability previously has been estimated to be 4.8%.2 In his model, Keen2 used 2 parameters: (1) an estimate of the absolute risk reduction of breast cancer mortality with mammography screening and (2) the cumulative incidence of screen-detected cancers. We have applied Keen's model to Danish data. During 1997 through 2006, 3 Danish municipalities had organized mammography screening (Copenhagen, Funen, and Frederiksberg). We were able to obtain data referring to the Copenhagen municipality. The number of screen-detected cancers from the first to seventh round (April 4, 1991, to December 31, 2005) has been published.3 We have obtained the number of screen-detected cancers over 5 rounds of screening (a 10-year period, from April 26, 1993–May 31, 2003). From the municipality population registry4 we obtained the midperiod number of women aged 50 to 69 years living in the Copenhagen municipality from January 1, 1993, through December 31, 2002. Using these 2 numbers, we estimated the incidence of screen-detected cancers over a 10-year period to be 20 per 1000 women aged 50 to 69 years. Assuming an absolute risk reduction of 1 breast cancer death per 2000 screened women,5 we have reached a P(life saved screen-detected cancer diagnosis) of 2.5%. We acknowledge that Welch and Frankel1 have been more cautious in their assumptions than we have. In doing so, they have avoided underestimation of any mammography effect, which only strengthens their main argument: for a breast cancer survivor, the probability that her life was saved by screening is, at most, 24%. Beyond the issue of the assumptions, we believe that the main explanation for the difference between estimates of P(life saved screen-detected cancer diagnosis) lies in the choice of measure used to quantify risk. In Keen's model (that we replicated using Danish data), a 10-year cumulative incidence is used. In the model by Welch and Frankel, a 20-year probability is used. For similar populations, these 2 risk measures provide numbers that are very different in terms of magnitude. This magnitude difference can leave clinicians and patients confused. We would like to invite Welch and Frankel to comment on the advantages of using probabilities conditioned on age when communicating with patients. Back to top Article Information Correspondence: Dr Heleno, Research Unit and Section for General Practice, University of Copenhagen, Øster Farimagsgade 5, Entrance Q, First Floor, PO Box 2099, Copenhagen K 1014, Denmark (bruno.heleno@sund.ku.dk). Financial Disclosure: None reported. References 1. Welch HG, Frankel BA. Likelihood that a woman with screen-detected breast cancer has had her “life saved” by that screening. Arch Intern Med. 2011;171(22):2043-204622025097PubMedGoogle ScholarCrossref 2. Keen JD. Promoting screening mammography: insight or uptake? J Am Board Fam Med. 2010;23(6):775-78221057074PubMedGoogle ScholarCrossref 3. Utzon-Frank N, Vejborg I, von Euler-Chelpin M, Lynge E. Balancing sensitivity and specificity: sixteen year's of experience from the mammography screening programme in Copenhagen, Denmark. Cancer Epidemiol. 2011;35(5):393-39821239242PubMedGoogle ScholarCrossref 4. Københavns Kommune. Personbiler: Statistikbanken. http://www.statistikbanken.dk/statbank5a/SelectTable/Omrade0.asp?PLanguage=1. Accessed December 19, 2011 5. Gøtzsche PC, Nielsen M. Screening for breast cancer with mammography. Cochrane Database Syst Rev. 2011;(1):CD00187721249649PubMedGoogle Scholar

Journal

Archives of Internal MedicineAmerican Medical Association

Published: Apr 23, 2012

Keywords: breast cancer,screening

References