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Does the Decrease in Hormone Replacement Therapy Also Affect Breast Cancer Risk in the Netherlands?

Department of Public Health, Rotterdam, the Netherlands

Marieke W.J. Louwman

Comprehensive Cancer Centre South, Eindhoven, the Netherlands

Otto Visser

Comprehensive Cancer Centre Amsterdam, Amsterdam, the Netherlands

Flora E. van Leeuwen

Netherlands Cancer Institute, Department of Epidemiology, Amsterdam, the Netherlands

To the Editor:

Recently, Robbins and Clarke¹ reported a sharp decrease in the incidence rate of first primary breast cancer in women throughout 50 years in the United States, which was attributed to a decrease in hormone replacement therapy (HRT) since 2001, consistent to an earlier study that was also done in the United States.² Although there was a similar decrease in HRT across Europe, such a remarkable decline in breast cancer rates has only been reported in Germany.³ Generally, women in Europe have shown a different pattern of HRT use than the United States, mostly less frequent use and of shorter durations.^4,5 Only 13% of women aged 49 to 70 years used HRT in the Netherlands between 1993 and 1997,⁵ versus 38% in the United States.⁴ In the Netherlands, HRT use decreased by 12% between 2002 and 2003, followed by another 26% between 2003 and 2004. By the end of 2005, there was a decrease of 42%, as compared to 2001, of combined estrogen-progesterone and natural and semiorganic estrogen use. However, the rate of first primary breast cancer among women aged 50 to 69 years in the northwestern and southeastern Netherlands had not changed until 2005 (Fig 1). The impact of the sudden fall of HRT use would account for about a 6% fall of breast cancer incidence in the United States versus only 0.4% in the Netherlands, using the following formula (p-p*)(relative risk [RR] – 1) / (p [RR –1] + 1)⁶ (p = past prevalence, p* = current prevalence and RR is 1.07 for the Netherlands for duration of use < 5 years and 1.25 for the United States for duration of use 5 years⁷). A similar small impact of decrease in HRT use on the breast cancer incidence is expected in low-use countries such as Spain or Italy (5% to 8%), which is in contrast to countries with a high use such as Belgium or France (32% to 38%).⁴ There is, however, another pitfall; HRT use has been related to increased breast density, thus reducing the specificity of mammography and delaying detection of 20% of breast cancer cases.⁸ The maximum benefit of HRT reduction should be evident within the next 2 years (data until 2007) in the Netherlands, where biannual mass screening with more than 80% attendance rate has been practiced since the early 1990s, and might take longer in the United States having only opportunistic screening with lower coverage and attendance rate.

View larger version (11K): [in this window] [in a new window] [PowerPoint Slide for Teaching]   Fig 1. Annual incidence of female breast cancer between the ages of 50 and 69 years in the Netherlands (NL) and in the United States (USA). US data are from nine of the Surveillance Epidemiology and End Results registries, and NL data are from two registries (northwest and southeast NL). Data of the NL for 2004 to 2005 (northwest) and 2003 to 2005 (southeast) are corrected for extra regional cases by adding the average number of extra regional cases in preceding years. Rates were age adjusted to the European standard population.

AUTHORS' DISCLOSURES OF POTENTIAL CONFLICTS OF INTEREST

The author(s) indicated no potential conflicts of interest.

ACKNOWLEDGMENTS

This study is financed by Eurocadet project (contract number: SP23-CT-2005-006528).

REFERENCES

1. Robbins AS, Clarke CA: Regional changes in hormone therapy use and breast cancer incidence in California from 2001 to 2004. J Clin Oncol 23 : 3437 -3439, 2007

2. Ravdin PM, Cronin KA, Howlader N, et al: The decrease in breast-cancer incidence in 2003 in the United States. N Engl J Med 356 : 1670 -1674, 2007[Abstract/Free Full Text]

3. Katalinic A, Rawal R: Decline in breast cancer incidence after decrease in utilisation of hormone replacement therapy. Breast Cancer Res Treat [epub ahead of print April 24, 2007]

4. Lundberg V, Tolonen H, Stegmayr B, et al: Use of oral contraceptives and hormone replacement therapy in the WHO MONICA project. Maturitas 48 : 39 -49, 2004[CrossRef][Medline]

5. van Duijnhoven FJ, van Gils CH, Bezemer ID, et al: Use of hormones in the menopausal transition period in the Netherlands between 1993 and 1997. Maturitas 53 : 462 -475, 2006[CrossRef][Medline]

6. Murray CJ, Ezzati M, Lopez AD, et al: Comparative quantification of health risks conceptual framework and methodological issues. Popul Health Metr 1 : 1 , 2003[CrossRef][Medline]

7. Breast cancer and hormone replacement therapy: Collaborative reanalysis of data from 51 epidemiological studies of 52,705 women with breast cancer and 108,411 women without breast cancer. Collaborative Group on Hormonal Factors in Breast Cancer. Lancet 350 : 1047 -1059, 1997[CrossRef][Medline]

8. Kavanagh AM, Mitchell H, Giles GG: Hormone replacement therapy and accuracy of mammographic screening. Lancet 355 : 270 -274, 2000[CrossRef][Medline]

9. Comprehensive cancer centres: http://www.ikcnet.nl

Related Reply

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• Regional Changes in Hormone Therapy Use and Breast Cancer Incidence in California From 2001 to 2004
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