Journal of the National Cancer Institute Advance Access originally published online on November 25, 2008
JNCI Journal of the National Cancer Institute 2008 100(23):1724-1733; doi:10.1093/jnci/djn388
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© The Author 2008. Published by Oxford University Press.
ARTICLES |
Obesity, Mammography Use and Accuracy, and Advanced Breast Cancer Risk
Affiliations of authors: Departments of Epidemiology and Biostatistics (KK) and General Internal Medicine Section, Department of Veterans Affairs, University of California, San Francisco, CA (KK); Group Health Center for Health Studies, Seattle, WA (RW, DLM, DSMB); Department of Biostatistics, University of Washington, Seattle, WA (DLM); Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, MD (AD); Applied Research Program, Division of Cancer Control and Population Sciences, National Cancer Institute, National Institutes of Health, Bethesda, MD (RBB)
Correspondence to: Karla Kerlikowske, MD, San Francisco Veterans Affairs Medical Center, General Internal Medicine Section, 111A1, 4150 Clement St, San Francisco, CA 94121 (e-mail: karla.kerlikowske{at}ucsf.edu).
Background: Being overweight or obese is associated with increased breast cancer risk and disease severity among postmenopausal women, but whether extent of mammography use and accuracy modify this association and further contribute to increases in disease severity at diagnosis among overweight and obese women is unclear.
Methods: We prospectively collected data during 1996–2005 on 287 115 postmenopausal women not using hormone therapy (HT) who underwent 614 562 mammography examinations; 4446 women were diagnosed with breast cancer within 12 months of a mammography examination. We calculated rates per 1000 mammography examinations of large (>15 mm), advanced-stage (IIb, III, or IV), high-grade (3 or 4), estrogen receptor (ER)–positive and –negative, and screen-detected and non–screen-detected breast cancer across body mass index (BMI, kg/m2) groups defined as normal (18.5–24.9), overweight (25.0–29.9), obese class I (30.0–34.9), and obese class II/III (
35.0), adjusting for age, race/ethnicity, and mammography registry and use. All statistical tests were two-sided.
Results: Adjusted rates per 1000 mammography examinations of overall breast cancer increased across BMI groups (6.6 normal, 7.4 overweight, 7.9 obese I, 8.5 obese II/III; Ptrend < .001), as did rates of advanced disease, including large invasive (2.3 normal, 2.6 overweight, 2.9 obese I, 3.2 obese II/III; Ptrend < .001), advanced-stage (0.8 normal, 0.9 overweight, 1.3 obese I, 1.5 obese II/III; Ptrend < .001), and high nuclear grade (1.5 normal, 1.7 overweight, 1.7 obese I, 1.9 obese II/III; Ptrend = .10) tumors. Rates of ER-positive tumors increased across BMI groups (Ptrend < .001); rates of ER-negative tumors did not. Rates of screen-detected cancers were higher among overweight and obese women than normal and underweight women, but rates of non–screen-detected (false-negative) cancers were similar. Rates of advanced breast cancer increased across BMI groups regardless of extent of mammography use.
Conclusions: Patterns of mammography use and mammography accuracy are not the primary reasons for higher rates of advanced breast cancer among overweight and obese postmenopausal women not using HT; thus, biologic differences in breast tumor development and/or progression may be important.
| CONTEXT AND CAVEATS Prior knowledge In postmenopausal women, obesity and being overweight are associated with increased risk of breast cancer and increased disease severity; however, it is unknown whether differences in mammography use and accuracy have a role in these associations. Study design Prospective study of rates of breast cancer among postmenopausal women not taking hormone therapy (HT) who underwent mammography during 1996–2005. Contribution Increased body mass index (BMI) was associated with increased rates of breast cancer overall and advanced-stage disease per 1000 mammography examinations; it was not associated with rates of non–screen-detected breast cancers. Implications In the population studied, differences in mammography use and accuracy do not explain the higher rates of breast cancer among overweight and obese postmenopausal women who are not using HT. Limitations BMI calculations were based on self-reported height and weight measurements, and overweight women often underestimate their weight. Because few black, Hispanic, Native American, and Native Alaskan women with breast cancer were included in the study, rates of advanced breast cancer by BMI category adjusted for mammography use could not be calculated for these subgroups. From the Editors
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Manuscript received May 17, 2008; revised September 1, 2008; accepted September 30, 2008.
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J Natl Cancer Inst 2008 100: 1657.
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