Journal of the National Cancer Institute Advance Access originally published online on April 8, 2008
JNCI Journal of the National Cancer Institute 2008 100(8):597-598; doi:10.1093/jnci/djn079
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© The Author 2008. Published by Oxford University Press.
CORRESPONDENCE |
Re: Declines in Invasive Breast Cancer and Use of Postmenopausal Hormone Therapy in a Screening Mammography Population
Affiliation of authors: Division of Research, Kaiser Permanente Medical Program of Northern California, Oakland, California
Correspondence to: Bette Caan, DrPH, Division of Research, Kaiser Permanente Medical Program of Northern California, 2000 Broadway, Oakland, CA 94612 (e-mail: bette.caan{at}kp.org).
We reported a recent drop in breast cancer incidence rates in US women (1), and others have observed this as well (2–4). Because of the marked decrease in breast cancer incidence around the time of the first report from the Women's Health Initiative (WHI) (5), we and others (1–4) have suggested that it may be due to discontinuation of hormone therapy among postmenopausal women. It also has been suggested that a drop in mammography rates, specifically among women who discontinued hormone therapy, may be another factor contributing to this observed decrease (2). Although two recent reports in the Journal (3,4) conclude that declines in screening mammography rates are unlikely to account for the recent decline in US breast cancer incidence, neither study examined whether women who were regular users of hormone therapy and then stopped soon after the WHI announcement had different patterns of mammography compared with women who continued using or never used hormones.
We used data from Kaiser Permanente of Northern California (KPNC), a large health maintenance organization, to examine this issue. Among female health plan members aged 45 years and older, we first generated age-standardized (to US Census 2000) semiannual incidence rates of breast cancer for the period January 2000 to June 2006 using data from the KPNC Cancer Registry. Using our electronic pharmacy database, we then categorized these women into four groups based on their pattern of hormone use before and after the WHI announcement, and we generated semiannual screening mammography rates for three of these groups (Figure 1) by linkage with our diagnostic imaging database. The remaining group not presented in Figure 1 are women whose pattern of hormone use did not fit into any of the three groups, such as women who used hormone therapy before July 2002 but did not use it regularly for at least 2 years or women who continued use after December 2002 but again not on a regular basis.
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This study was approved by the KPNC Institutional Review Board. In our population, mammography rates (6-month intervals) and breast cancer incidence rates are associated, and both decreased in 2003 (Figure 1). The greatest decrease in mammography rates was seen in women who were regularly using hormones before 2002 but stopped by December 2002, within 6 months after the WHI announcement. These stoppers had a slight increase in the mammography screening rate in the latter half of 2002 and then a substantial decrease in 2003 (>20%). These data suggest that the decline in cancer incidence after 2002 in our population may in part reflect a drop in mammography screening among women who were regular hormone users but who stopped around the time of the announcement of WHI findings. However, studies with individual data on hormone use, mammography, and breast cancer incidence are needed to further elucidate the contribution of hormone use and mammography, or other factors, to the recent drop in breast cancer rates.
REFERENCES
1. Clarke CA, Glaser SL, Uratsu CS, Selby JV, Kushi LH, Herrinton LJ. Recent declines in hormone therapy utilization and breast cancer incidence: clinical and population-based evidence. J Clin Oncol (2006) 24(33):e49–e50.
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 (2007) 356(16):1670–1674.
3. Glass AG, Lacey JV Jr, Carreon JD, Hoover RN. Breast cancer incidence, 1980–2006: combined roles of menopausal hormone therapy, screening mammography, and estrogen receptor status. J Natl Cancer Inst (2007) 99(15):1152–1161.
4. Kerlikowske K, Miglioretti DL, Buist DS, Walker R, Carney PA. Declines in invasive breast cancer and use of postmenopausal hormone therapy in a screening mammography population. J Natl Cancer Inst (2007) 99(17):1335–1339.
5. Rossouw JE, Anderson GL, Prentice RL, et al. Risks and benefits of estrogen plus progestin in healthy postmenopausal women: principal results from the Women's Health Initiative randomized controlled trial. JAMA (2002) 288(3):321–333.
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J Natl Cancer Inst 2008 100: 599.
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