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Mammographic density and risk of breast cancer by adiposity: An analysis of four case‐control studies
Author(s) -
Conroy Shan M.,
Woolcott Christy G.,
Koga Karin R.,
Byrne Celia,
Nagata Chisato,
Ursin Giske,
Vachon Celine M.,
Yaffe Martin J.,
Pagano Ian,
Maskarinec Gertraud
Publication year - 2011
Publication title -
international journal of cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.475
H-Index - 234
eISSN - 1097-0215
pISSN - 0020-7136
DOI - 10.1002/ijc.26205
Subject(s) - medicine , body mass index , overweight , odds ratio , confounding , breast cancer , confidence interval , mammographic density , logistic regression , obesity , demography , cancer , mammography , gynecology , sociology
The association of mammographic breast density with breast cancer risk may vary by adiposity. To examine effect modification by body mass index (BMI), the authors standardized mammographic density data from four case‐control studies (1994–2002) conducted in California, Hawaii and Minnesota and Gifu, Japan. The 1,699 cases and 2,422 controls included 45% Caucasians, 40% Asians and 9% African‐Americans. Using ethnic‐specific BMI cut points, 34% were classified as overweight and 19% as obese. A single reader assessed density from mammographic images using a computer‐assisted method. Logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (95% CI) while adjusting for potential confounders. Modest heterogeneity in the relation between percent density and breast cancer risk across studies was observed ( p heterogeneity = 0.08). Cases had a greater age‐adjusted mean percent density than controls: 31.7% versus 28.5%, respectively ( p <0.001). Relative to <20 percent density, the ORs for >35 were similar across BMI groups whereas the OR for 20‐35 was slightly higher in overweight (OR = 1.69, 95% CI: 1.28, 2.24) and obese (OR = 1.62, 95% CI: 1.12, 2.33) than in normal weight women (OR = 1.49, 95% CI: 1.11, 2.01). Furthermore, limited evidence of effect modification by BMI of the OR per 10% increase in percent density ( p interaction = 0.06) was observed, including subgroup analyses by menopausal status and in analyses that excluded women at the extremes of the BMI scale. Our findings indicate little, if any, modification by BMI of the effects of breast density on breast cancer risk.