Boyd Norman F, Martin Lisa J, Sun Limei, Guo Helen, Chiarelli Anna, Hislop Greg, Yaffe Martin, Minkin Salomon
Campbell Family Institute for Breast Cancer Research, Ontario Cancer Institute, Toronto, Ontario, Canada M5G 2K9.
Cancer Epidemiol Biomarkers Prev. 2006 Nov;15(11):2086-92. doi: 10.1158/1055-9965.EPI-06-0345.
Greater weight and body mass index (BMI) are negatively correlated with mammographic density, a strong risk factor for breast cancer, and are associated with an increased risk of breast cancer in postmenopausal women, but with a reduced risk in premenopausal women. We have examined the associations of body size and mammographic density on breast cancer risk.
We examined the associations of body size and the percentage of mammographic density at baseline with subsequent risk of breast cancer among 1,114 matched case-control pairs identified from three screening programs. The effect of each factor on risk of breast cancer was examined before and after adjustment for the other, using logistic regression.
In all subjects, before adjustment for mammographic density, breast cancer risk in the highest quintile of BMI, compared with the lowest, was 1.04 [95% confidence interval (CI), 0.8-1.4]. BMI was associated positively with breast cancer risk in postmenopausal women, and negatively in premenopausal women. After adjustment for density, the risk associated with BMI in all subjects increased to 1.60 (95% CI, 1.2-2.2), and was positive in both menopausal groups. Adjustment for BMI increased breast cancer risk in women with 75% or greater density, compared with 0%, increased from 4.25 (95% CI, 1.6-11.1) to 5.86 (95% CI, 2.2-15.6).
BMI and mammographic density are independent risk factors for breast cancer, and likely to operate through different pathways. The strong negative correlated between them will lead to underestimation of the effects on risk of either pathway if confounding is not controlled.
更大的体重和体重指数（BMI）与乳腺钼靶密度呈负相关，乳腺钼靶密度是乳腺癌的一个重要危险因素，且与绝经后女性患乳腺癌风险增加相关，但与绝经前女性患癌风险降低有关。我们研究了体型和乳腺钼靶密度与乳腺癌风险之间的关联。
我们在从三个筛查项目中识别出的1114对匹配的病例对照中，研究了基线时的体型和乳腺钼靶密度百分比与后续患乳腺癌风险之间的关联。使用逻辑回归分析了每个因素在调整另一个因素前后对乳腺癌风险的影响。
在所有受试者中，在调整乳腺钼靶密度之前，BMI最高五分位数组的乳腺癌风险与最低五分位数组相比为1.04[95%置信区间（CI），0.8 - 1.4]。BMI与绝经后女性的乳腺癌风险呈正相关，与绝经前女性呈负相关。调整密度后，所有受试者中与BMI相关的风险增加到1.60（95%CI，1.2 - 2.2），且在两个绝经组中均为正相关。与0%相比，调整BMI后，密度为75%或更高的女性患乳腺癌风险从4.25（95%CI，1.6 - 11.1）增加到5.86（95%CI，2.2 - 15.6）。
BMI和乳腺钼靶密度是乳腺癌的独立危险因素，且可能通过不同途径起作用。如果不控制混杂因素，它们之间的强负相关会导致对任何一条途径的风险影响估计不足。
