Estimating Age-Specific Mean Sojourn Time of Breast Cancer and Sensitivity of Mammographic Screening by Breast Density among Korean Women

Background: High breast cancer incidence among women in forties are specific to Asian, implicating dense breast. This study examined the natural history of breast cancer progression among Korean women according to the levels of breast density.Methods: We applied a three-state Markov model to fit the natural history of breast cancer to data in the Korean National Cancer Screening Program. Diagnosis of breast cancer was ascertained by linkage to the Korean Central Cancer Registry. Disease progression rates (i.e., transition rates from healthy to preclinical state, and from preclinical to clinical state) were estimated across levels of breast density determined by the Breast Imaging, Reporting and Data System (BI-RADS). Preclinical incidence of breast cancer, mean sojourn time (MST) and mammographic screening sensitivity were simultaneously generated in the model.Results: Overall prevalence of dense breast among Korean women was 53.9%, which declined with age. Transition rate from healthy to preclinical state, indicating the preclinical incidence of breast cancer, was estimated to be higher among women aged 40-49 years (0.0019, 95% CI; 0.0017-0.0021) and women aged 50-59 years (0.0020, 95% CI; 0.0017-0.0022), than older women aged 60-69 years (0.0014, 95% CI; 0.0012-0.0017). Transition rate from preclinical to clinical state was also fastest among younger age groups, which directly translated to the shortest MSTs, estimated as 1.98 (95% CI; 1.67-2.33), 2.49 (95% CI; 1.92-3.22) and 3.07 (95% CI; 2.11-4.46) years for women in forties, fifties and sixties, respectively. The sensitivity of the mammographic screening was higher among older women (0.70, 95% CI; 0.62-0.77) than women in fifties (0.65, 95% CI; 0.62-0.77) and women in forties (0.61, 95% CI; 0.54-0.61). Having dense breasts increased the likelihood of the preclinical cancer risk (1.96 to 2.35 times) and decreased the duration of MST (1.53 to 2.02 times).Conclusions: Korean women showed 1.5 to 2 times higher prevalence of dense breast tissues, compared to Western women. This study estimated Korean-specific parameters for the natural history of breast cancer that would be utilized for establishing optimal screening strategies in countries with higher dense breast prevalence.