调整体质量指数分析体积乳腺密度与乳腺癌风险。
Adjusting for BMI in analyses of volumetric mammographic density and breast cancer risk.
机构信息
Department of Non-Communicable Disease Epidemiology, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK.
Cancer Registry of Norway, Institute of Population-based Cancer Research, Oslo, Norway.
出版信息
Breast Cancer Res. 2018 Dec 29;20(1):156. doi: 10.1186/s13058-018-1078-8.
BACKGROUND
Fully automated assessment of mammographic density (MD), a biomarker of breast cancer risk, is being increasingly performed in screening settings. However, data on body mass index (BMI), a confounder of the MD-risk association, are not routinely collected at screening. We investigated whether the amount of fat in the breast, as captured by the amount of mammographic non-dense tissue seen on the mammographic image, can be used as a proxy for BMI when data on the latter are unavailable.
METHODS
Data from a UK case control study (numbers of cases/controls: 414/685) and a Norwegian cohort study (numbers of cases/non-cases: 657/61059), both with volumetric MD measurements (dense volume (DV), non-dense volume (NDV) and percent density (%MD)) from screening-age women, were analysed. BMI (self-reported) and NDV were taken as measures of adiposity. Correlations between BMI and NDV, %MD and DV were examined after log-transformation and adjustment for age, menopausal status and parity. Logistic regression models were fitted to the UK study, and Cox regression models to the Norwegian study, to assess associations between MD and breast cancer risk, expressed as odds/hazard ratios per adjusted standard deviation (OPERA). Adjustments were first made for standard risk factors except BMI (minimally adjusted models) and then also for BMI or NDV. OPERA pooled relative risks (RRs) were estimated by fixed-effect models, and between-study heterogeneity was assessed by the I statistics.
RESULTS
BMI was positively correlated with NDV (adjusted r = 0.74 in the UK study and r = 0.72 in the Norwegian study) and with DV (r = 0.33 and r = 0.25, respectively). Both %MD and DV were positively associated with breast cancer risk in minimally adjusted models (pooled OPERA RR (95% confidence interval): 1.34 (1.25, 1.43) and 1.46 (1.36, 1.56), respectively; I = 0%, P >0.48 for both). Further adjustment for BMI or NDV strengthened the %MD-risk association (1.51 (1.41, 1.61); I = 0%, P = 0.33 and 1.51 (1.41, 1.61); I = 0%, P = 0.32, respectively). Adjusting for BMI or NDV marginally affected the magnitude of the DV-risk association (1.44 (1.34, 1.54); I = 0%, P = 0.87 and 1.49 (1.40, 1.60); I = 0%, P = 0.36, respectively).
CONCLUSIONS
When volumetric MD-breast cancer risk associations are investigated, NDV can be used as a measure of adiposity when BMI data are unavailable.
背景
在筛查环境中，越来越多地对乳腺密度（MD）进行全自动评估，MD 是乳腺癌风险的生物标志物。然而，在筛查时通常不会收集到身体质量指数（BMI）数据，而 BMI 是 MD 与风险关联的混杂因素。我们研究了当没有 BMI 数据时，乳腺钼靶图像上可见的乳腺非致密组织量能否作为 BMI 的替代指标来评估乳腺内脂肪量。
方法
对来自英国病例对照研究（病例/对照数量：414/685）和挪威队列研究（病例/非病例数量：657/61059）的数据进行了分析，这两项研究均对筛查年龄段女性进行了容积性 MD 测量（致密体积（DV）、非致密体积（NDV）和密度百分比（%MD））。BMI（自我报告）和 NDV 被用作肥胖的衡量指标。对 log 转换后并按年龄、绝经状态和生育史调整的 BMI 和 NDV、%MD 和 DV 之间的相关性进行了检查。在英国研究中拟合了逻辑回归模型，在挪威研究中拟合了 Cox 回归模型，以评估 MD 与乳腺癌风险之间的关联，以调整后的标准偏差表示为优势比/风险比（OPERA）。首先，在最小调整模型中，除 BMI 外，对标准风险因素进行了调整（最小调整模型），然后还对 BMI 或 NDV 进行了调整。通过固定效应模型估计了 OPERA 汇总相对风险（RR），并通过 I 统计量评估了研究间的异质性。
结果
BMI 与 NDV 呈正相关（英国研究中的调整后 r = 0.74，挪威研究中的 r = 0.72），与 DV 也呈正相关（r = 0.33 和 r = 0.25）。%MD 和 DV 在最小调整模型中均与乳腺癌风险呈正相关（汇总 OPERA RR（95%置信区间）：1.34（1.25，1.43）和 1.46（1.36，1.56）；I = 0%，P>0.48 均为）。进一步调整 BMI 或 NDV 可增强%MD 风险关联（1.51（1.41，1.61）；I = 0%，P = 0.33 和 1.51（1.41，1.61）；I = 0%，P = 0.32）。调整 BMI 或 NDV 对 DV 风险关联的程度略有影响（1.44（1.34，1.54）；I = 0%，P = 0.87 和 1.49（1.40，1.60）；I = 0%，P = 0.36）。
结论
当研究容积性 MD-乳腺癌风险关联时，当 BMI 数据不可用时，NDV 可以用作肥胖的衡量指标。
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