Channing Laboratory, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, 181 Longwood Avenue, Boston, MA 02115, USA.
Breast Cancer Res. 2011 Oct 21;13(5):R100. doi: 10.1186/bcr3041.
The mechanisms underlying the strong association between percentage dense area on a mammogram and the risk of breast cancer are unknown. We investigated separately the absolute dense area and the absolute nondense area on mammograms in relation to breast cancer risk.
We conducted a nested case-control study on prediagnostic mammographic density measurements and risk of breast cancer in the Nurses' Health Study and the Nurses' Health Study II. Premenopausal mammograms were available from 464 cases and 998 controls, and postmenopausal mammograms were available from 960 cases and 1,662 controls. We used a computer-assisted thresholding technique to measure mammographic density, and we used unconditional logistic regression to calculate OR and 95% CI data.
Higher absolute dense area was associated with a greater risk of breast cancer among premenopausal women (OR(tertile 3 vs 1) = 2.01, 95% CI = 1.45 to 2.77) and among postmenopausal women (OR(quintile 5 vs 1) = 2.19, 95% CI = 1.65 to 2.89). However, increasing absolute nondense area was associated with a decreased risk of breast cancer among premenopausal women (OR(tertile 3 vs 1) = 0.51, 95% CI = 0.36 to 0.72) and among postmenopausal women (OR(quintile 5 vs 1) = 0.46, 95% CI = 0.34 to 0.62). These associations changed minimally when we included both absolute dense area and absolute nondense area in the same statistical model. As expected, the percentage dense area was the strongest risk factor for breast cancer in both groups.
Our results indicate that absolute dense area is independently and positively associated with breast cancer risk, whereas absolute nondense area is independently and inversely associated with breast cancer risk. Since adipose tissue is radiographically nondense, these results suggest that adipose breast tissue may have a protective role in breast carcinogenesis.
在乳房 X 线照相术上的百分比致密区与乳腺癌风险之间存在强烈关联的机制尚不清楚。我们分别研究了乳房 X 线照相术上的绝对致密区和绝对非致密区与乳腺癌风险的关系。
我们在护士健康研究和护士健康研究 II 中进行了一项基于诊断前乳房 X 线密度测量值和乳腺癌风险的巢式病例对照研究。在绝经前的乳房 X 线照片中，可获得 464 例病例和 998 例对照，在绝经后的乳房 X 线照片中，可获得 960 例病例和 1662 例对照。我们使用计算机辅助阈值技术来测量乳房 X 线照相术的密度，并使用无条件逻辑回归来计算 OR 和 95%CI 数据。
在绝经前妇女中，较高的绝对致密区与乳腺癌风险增加相关（OR（三分位 3 与 1）= 2.01，95%CI = 1.45 至 2.77），在绝经后妇女中，较高的绝对致密区与乳腺癌风险增加相关（OR（五分位 5 与 1）= 2.19，95%CI = 1.65 至 2.89）。然而，在绝经前妇女（OR（三分位 3 与 1）= 0.51，95%CI = 0.36 至 0.72）和绝经后妇女（OR（五分位 5 与 1）= 0.46，95%CI = 0.34 至 0.62）中，增加的绝对非致密区与乳腺癌风险降低相关。当我们将绝对致密区和绝对非致密区同时包含在相同的统计模型中时，这些关联变化不大。正如预期的那样，在这两个组中，百分比致密区是乳腺癌最强的危险因素。
我们的结果表明，绝对致密区独立且正向与乳腺癌风险相关，而绝对非致密区独立且负向与乳腺癌风险相关。由于脂肪组织在影像学上是非致密的，这些结果表明，乳腺脂肪组织可能在乳腺癌发生过程中具有保护作用。
