Estimates of overdiagnosis of invasive breast cancer associated with screening mammography
To estimate the extent of overdiagnosis of invasive breast cancer associated with screening in New South Wales, Australia, a population with a well-established mammography screening program which has achieved full geographic coverage.
We calculated overdiagnosis as the observed annual incidence of invasive breast cancer in NSW in 1999–2001 (a screened population) minus the expected annual incidence in this population at the same time, as a percentage of the expected incidence. We estimated expected incidence without screening in 1999–2001 from the incidence of invasive breast cancer in: (1) women in unscreened age groups (interpolation method); and (2) women in all age groups prior to the implementation of screening (extrapolation method). We then adjusted these estimates for trends in major risk factors for breast cancer that may have coincided with the introduction of mammography screening: increasing obesity, use of hormone replacement therapy (HRT) and nulliparity. Finally, we adjusted for lead time to produce estimates of expected incidence in 1999–2001. These were compared with the observed incidence in 1999–2001 to calculate overdiagnosis of breast cancer associated with screening.
Overdiagnosis of invasive breast cancer among 50–69 year NSW women was estimated to be 42 and 30% using the interpolation and extrapolation methods, respectively.
Overdiagnosis of invasive breast cancer attributable to mammography screening appears to be substantial. Our estimates are similar to recent estimates from other screening programmes. Overdiagnosis merits greater attention in research and in clinical and public health policy making.
KeywordsBreast cancer incidence Mammography screening Overdiagnosis
- 2.Australian Institute of Health and Welfare (2003) BreastScreen Australia Monitoring Reports 1998–99, 1999–2000 and 2000–2001. Cancer series numbers 25 and 26; AIHW Cat.Nos. CAN 20 and CAN 21. Canberra, AIHWGoogle Scholar
- 15.Australian Institute of Health and Welfare (AIHW) Analysis of the 1980, 1983 and 1989 risk factor prevalence surveys, 1995 National Nutrition Survey and 1999–2000 Australian diabetes, obesity and lifestyle (AusDiab) study. Accessed from http://www.aihw.gov.au/dataonline/riskfactors/index.cfm
- 16.Australian Bureau of Statistics (2005) Births, Australia, 2005. 2006; cat. no. 3301.0. ABS, CanberraGoogle Scholar
- 21.Morimoto LM, White E, Chen Z, Chlebowski RT, Hays J, Kuller L, Lopez AM, Manson J, Margolis KL, Muti PC, Stefanick ML, McTiernan A (2002) Obesity, body size, and risk of postmenopausal breast cancer: The women’s health initiative (United States). Cancer Causes Control 13(8):741–751CrossRefPubMedGoogle Scholar
- 25.Estoesta JV, Gao K, Taylor RJ, Ho C, Brassil AE (2004) BreastScreen New South Wales Statistical Report: 1999–2002. BreastScreen NSW, SydneyGoogle Scholar
- 26.Day N (1987) Cumulative rate and cumulative risk. In: Muir C, Waterhouse J, Mack T et al (eds) Cancer incidence in five continents, Vol 5. [Chapter 10]. International Agency for Research on Cancer, Lyon (IARC Sci Publ No 88.)Google Scholar
- 27.SAS Institute Inc. (1999) SAS: statistical software. Version 8.02. SAS Institute, CaryGoogle Scholar
- 33.Gotzsche PC, Nielsen M (2006) Screening for breast cancer with mammography [Systematic Review] Cochrane Database of systematic reviewsGoogle Scholar
- 40.van de Vijver MJ, He YD, Van’t Veer LJ, Dai H, Hart AA, Voskuil DW, Schreiber GJ, Peterse JL, Roberts C, Marton MJ, Parrish M, Atsma D, Witteveen A, Glas A, Delahaye L, van der Velde T, Bartelink H, Rodenhuis S, Rutgers ET, Friend SH, Bernards R (2002) A gene-expression signature as a predictor of survival in breast cancer. N Engl J Med 347(25):1999–2009CrossRefPubMedGoogle Scholar