Background: The aim of this study was to investigate the relationship between changes in breast density during menopause and breast cancer risk. Methods: This study was a retrospective, longitudinal cohort study for women over 30 years of age who had undergone breast mammography serially at baseline and postmenopause during regular health checkups at Samsung Medical Center. None of the participants had been diagnosed with breast cancer at baseline. Mammographic breast density was measured using the American College of Radiology Breast Imaging Reporting and Data System. Results: During 18,615 person-years of follow-up (median follow-up 4.8 years; interquartile range 2.8–7.5 years), 45 participants were diagnosed with breast cancer. The prevalence of dense breasts was higher in those who were younger, underweight, had low parity or using contraceptives. The cumulative incidence of breast cancer increased 4 years after menopause in participants, and the consistently extremely dense group had a significantly higher cumulative incidence (CI) of breast cancer compared with other groups [CI of extremely dense vs. others (incidence rate per 100,000 person-years): 375 vs. 203, P < 0.01]. Conclusion: Korean women whose breast density was extremely dense before menopause and who maintained this density after menopause were at two-fold greater risk of breast cancer. Prevention Relevance: Extremely dense breast density that is maintained persistently from premenopause to postmenopause increases risk of breast cancer two fold in Korean women. Therefore, women having risk factors should receive mammography frequently and if persistently extremely dense breast had been detected, additional modalities of BC screening could be considered.

中文翻译：

---

韩国女性更年期乳房密度变化与乳腺癌风险的关系

背景：本研究的目的是调查绝经期间乳房密度变化与乳腺癌风险之间的关系。方法：本研究是一项回顾性纵向队列研究，对象为 30 岁以上女性，她们在三星医疗中心定期健康检查期间在基线和绝经后连续接受了乳房 X 光检查。没有参与者在基线时被诊断出患有乳腺癌。使用美国放射学会乳腺成像报告和数据系统测量乳腺 X 线照相术的密度。结果：在 18,615 人年的随访中（中位随访 4.8 年；四分位距 2.8-7.5 年），45 名参与者被诊断出患有乳腺癌。在年轻、体重过轻、胎次低或使用避孕药。参与者绝经后 4 年的乳腺癌累积发病率增加，与其他组相比，持续极高密度组的乳腺癌累积发病率 (CI) 显着更高 [CI 极密组与其他组（每 100,000 人的发病率） -年）：375 与 203，P < 0.01]。结论：绝经前乳房密度极高且在绝经后保持这种密度的韩国女性患乳腺癌的风险高出两倍。预防相关性：从绝经前到绝经后持续保持极高密度的乳房密度会使韩国女性患乳腺癌的风险增加两倍。所以，