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The recently published report from Ereman and colleagues [1] was intended to summarize recent trends in breast cancer incidence, mammography screening rates and hormone therapy (HT) use in non-Hispanic, white women (NHW) ≥ 50 years old in Marin County, California. The authors state that Marin County showed an excessively high incidence of breast cancer throughout the 1990s. They assemble tables and graphs that are used to suggest that a large drop in estrogen/progestin hormone therapy (EPHT), attributed to the 2002 media reporting on the Women’s Health Initiative (WHI), by 2004 resulted in a concomitantly reduced incidence of invasive breast cancer with no decline in mammography utilization. Further, they report a concomitant drop in estrogen receptor-positive (ER+) tumors. They also show that the incidence rates appear to have bottomed out and began rising after 2004 without reaching statistical significance. 

 

The prevalence estimates for each HT were supplied from a 2006–2007 survey taken from 1083 Marin County NHW women ≥ 50 years attending mammography screening. A total of 18% reported having undergone a hysterectomy. The women were asked to report what regimen they took now, and remember what their history of HT use was. The authors report that postmenopausal HT use decreased from 1995 to 2006: the use of estrogen hormone therapy (EHT) decreased by 15.4% (from about 25% to 22.4%) and the use of EPHT by 58.9% (from about 21–22% to 6.7%)

 

The prevalence estimates for mammography derive from a second source. The authors used an online tool on the National Cancer Institute (NCI)’s ‘AskCHIS’ to calculate the mammography prevalence in 2001 and compare it with the prevalence in 2004. This used random-digit dialing to homes (white race not specified) and the women who answered were asked if they ever had had a mammogram, and when most recently. No data were available on first vs. rescreening. The authors report that the prevalence of mammography screen was ≥ 85% in 2001 and 2004, i.e. essentially unchanged in these two groups. 

 

Breast cancer incidence rates are gathered from a third source. The Survey for Epidemiologic and End Results Program (SEER) data banks of the NCI sourced specifically for Marin County, ‘age adjusted data to the 2000 US population standard’. The authors report that invasive breast cancer rates from 1990 to 2007 for NHW ≥ 50 years old reached their absolute peak in 1999: 522/100,000. Translating this to a more readable ‘% of women’ yields incidence rates of 0.52% (95% confidence interval (CI) 0.45–0.60%) in 1999; 0.34% (95% CI 0.29–0.41%) in 2004; and 0.45% (95% CI 0.39–0.52%) in 2007. They further state ‘These results also were paralleled specifically by the ER+ tumors’.

 

Combining information from these three sets of data, the authors suggest that, if the population estimates for given years are correct, then the incidence declines in parallel with the EPHT decreases, and that breast cancer incidence seems now to be rising again, although such a trend would need to continue to achieve statistical significance.

Author(s)

  • Winnifred Cutler
    Athena Institute for Womens Wellness, Chester Springs, PA, USA
  • Regula Burki
    Berne, Switzerland

Citations

  1. Ereman RR, Prebil LA, Mockus M, et al. Recent trends in hormone therapy utilization and breast cancer incidence rate in the high incidence population of Marin County, California. BMC Public Health 2010;10:228.
    http://www.ncbi.nlm.nih.gov/pubmed/20433756
  2. Fournier A, Berrino F, Clavel-Chapelon F. Unequal risks for breast cancer associated with different hormone replacement therapies: results from the E3N cohort study. Breast Cancer Res Treat 2008;107:103-11.
    http://www.ncbi.nlm.nih.gov/pubmed/17333341
  3. Lyytinen H, Pukkala E, Ylikorkala O. Breast cancer risk in postmenopausal women using estradiol-progestogen therapy. Obstet Gynecol 2009;113:65-73.
    http://www.ncbi.nlm.nih.gov/pubmed/19104361
  4. Franke H, Vermes I. Differential effects of progestogens on breast cancer cell lines. Maturitas 2003;46(Suppl 1):S55-8.
    http://www.ncbi.nlm.nih.gov/pubmed/14670646
  5. Phipps AI, Clarke CA, Ereman RR. Impact of intercensal population projections and error of closure on breast cancer surveillance: examples from 10 California counties. Breast Cancer Res 2005;7:R655-60.
    http://www.ncbi.nlm.nih.gov/pubmed/16168110
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