Crandall Carolyn, Palla Shana, Reboussin Beth A, Ursin Giske, Greendale Gail A
Division of General Internal Medicine, David Geffen School of Medicine at University of California, Los Angeles, CA, USA.
Breast Cancer Res. 2005;7(6):R922-8. doi: 10.1186/bcr1327. Epub 2005 Sep 22.
Mammographic breast density is a strong independent risk factor for breast cancer. We hypothesized that demonstration of an association between mammographic breast density and bone mineral density (BMD) would suggest a unifying underlying mechanism influencing both breast density and BMD.
In a cross-sectional analysis of baseline data from the Postmenopausal Estrogen/Progestin Interventions Study (PEPI), participants were aged 45 to 64 years and were at least 1 year postmenopausal. Mammographic breast density (percentage of the breast composed of dense tissue), the outcome, was assessed with a computer-assisted percentage-density method. BMD, the primary predictor, was measured with dual-energy X-ray absorptiometry. Women quitting menopausal hormone therapy to join PEPI were designated recent hormone users.
The mean age of the 594 women was 56 years. The average time since menopause was 5.6 years. After adjustment for age, body mass index, and cigarette smoking, in women who were not recent hormone users before trial enrollment (n = 415), mammographic density was positively associated with total hip (P = 0.04) and lumbar (P = 0.08) BMD. Mammographic density of recent hormone users (n = 171) was not significantly related to either total hip (P = 0.51) or lumbar (P = 0.44) BMD. In participants who were not recent hormone users, mammographic density was 4% greater in the highest quartile of total hip BMD than in the lowest. In participants who were not recent hormone users, mammographic density was 5% greater in the highest quartile of lumbar spine BMD than in the lowest.
Mammographic density and BMD are positively associated in women who have not recently used postmenopausal hormones. A unifying biological mechanism may link mammographic density and BMD. Recent exogenous postmenopausal hormone use may obscure the association between mammographic density and BMD by having a persistent effect on breast tissue.
乳腺钼靶密度是乳腺癌的一个强有力的独立危险因素。我们推测，证明乳腺钼靶密度与骨矿物质密度（BMD）之间存在关联，将提示存在一种影响乳腺密度和骨密度的统一潜在机制。
在绝经后雌激素/孕激素干预研究（PEPI）的基线数据横断面分析中，参与者年龄在45至64岁之间，且绝经至少1年。采用计算机辅助百分比密度法评估乳腺钼靶密度（乳腺致密组织所占百分比）这一结果。用双能X线吸收法测量主要预测指标骨密度。退出绝经激素治疗而加入PEPI的女性被指定为近期激素使用者。
594名女性的平均年龄为56岁。绝经后的平均时间为5.6年。在试验入组前不是近期激素使用者的女性（n = 415）中，调整年龄、体重指数和吸烟因素后，乳腺钼靶密度与全髋部（P = 0.04）和腰椎（P = 0.08）骨密度呈正相关。近期激素使用者（n = 171）的乳腺钼靶密度与全髋部（P = 0.51）或腰椎（P = 0.44）骨密度均无显著相关性。在不是近期激素使用者的参与者中，全髋部骨密度最高四分位数组的乳腺钼靶密度比最低四分位数组高4%。在不是近期激素使用者的参与者中，腰椎骨密度最高四分位数组比最低四分位数组的乳腺钼靶密度高5%。
在近期未使用绝经后激素的女性中，乳腺钼靶密度与骨密度呈正相关。一种统一的生物学机制可能将乳腺钼靶密度和骨密度联系起来。近期外源性绝经后激素的使用可能通过对乳腺组织产生持续影响而掩盖乳腺钼靶密度与骨密度之间的关联。
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