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ARTICLES: Asma Ghafoor, Ahmedin Jemal, Elizabeth Ward, Vilma Cokkinides, Robert Smith, and Michael Thun Trends in Breast Cancer by Race and Ethnicity CA Cancer J Clin 2003; 53: 342-355 [Abstract] [Full text] [PDF]

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RE: Trends in Breast Cancer by Race and Ethnicity

Kliewer Erich, Alain Demers   (30 September 2004)

RE: Trends in Breast Cancer by Race and Ethnicity 30 September 2004
Kliewer Erich CancerCare Mannitoba, Alain Demers Send letter to journal: Re: RE: Trends in Breast Cancer by Race and Ethnicity Erich.Kliewer{at}cancercare.mb.ca Kliewer Erich, et al.	Ghafoor et al. reported that there was an average annual increase of 1.7% in the incidence of large (>5 cm) breast cancer tumors during the period 1992-2000 in the United States.1 The increase was greatest among White women (2.1%). Using data from the Manitoba Cancer Registry, we calculated the annual age-standardized incidence rate (ASIR) (2000 standard million population) by tumor size and used Joinpoint to estimate the annual percent change over the period 1995-2001. The overall ASIR during this period was 119.6 per 100,000 and the estimated annual percent change (APC) was -0.6%. Similar to the United States, in Manitoba the incidence of tumors less than or equal to 2 cm increased (APC 1.4) and the incidence of tumors sized 2.1 cm -5.0 cm decreased (APC -1.7). However, unlike the United States, the incidence of the largest tumors (>5.0 cm) decreased in Manitoba (APC -3.4%), although the decrease was not statistically significant. It is not clear why the incidence of large breast cancer tumors should be increasing in the United States, but decreasing in Manitoba. The proportion of women screened has been increasing in the 1990s in both countries, and in 1997 the proportion of women aged 50-69 years (Canada’s recommended screening age) who had a mammogram in the last two years was comparable.2,3 With the increase in screening one would expect to see an increase in the incidence of smaller tumors and a gradual decrease in the incidence of larger tumors. Ghafoor et al. suggested that the increase observed in the United States may be due to an increasing prevalence of postmenopausal obesity and HRT use.1 Although a more sophisticated analysis would have to be undertaken in order to examine the roles of these two factors in the incidence of large breast cancer tumors, in Canada there has also been increases in obesity4 and the levels of HRT use5 without the corresponding increase in large tumors, at least not in Manitoba. 1. Ghafoor A, Jemal A, Ward E, et al. Trends in breast cancer by race and ethnicity. CA Cancer J Clin 2003;53:342-355. 2. Federal, Provincial and Territorial Advisory Committee on Population Health. Statistical Report on the Health of Canadians. Ottawa: Statistics Canada, Catalogue No:82-570-X1E, 1999. 3. Blackman DK, Bennett EM, Miller DS. MMWR CDC Surveill Summ 1999;48(6):1-22. 4. Katzmarzyk PT. The Canadian obesity epidemic: an historical perspective. Obes Res 2002;10(7):666-674. 5. Wilkins K. Hormone replacement therapy and incident arthritis. Health Reports 1999;11(2):49-57. Table 1. Trends in the ASIR by Tumor Size, Manitoba 1995-2001 Size N ASIR APC 95% CI 0-2.0 3,184 73.4 1.4 -0.3,3.0 2.1-5.0 1,466 33.7 -1.7 -5.7,2.4 >5.0 230 5.3 -3.4 -10.4,4.2 Total1 5,120 119.6 -0.6 -2.3,1.2 1. CI, Confidence interval. 2. There were 240 cases for which tumor size was unknown.