The epidemiological characteristics of breast cancer in Korean women are different from the characteristics reported in Western women. The highest incidence rate occurs in Korean women in their 40s. The purpose of this study was to determine the most cost-effective screening interval and target age range for Korean women from the perspective of the national healthcare system. A stochastic model was used to simulate breast cancer screenings by varying both the screening intervals and the age ranges. The effectiveness of mammography screening was defined as the probability of detecting breast cancer in the preclinical state and the cost was based on the direct cost of mammography screening and the confirmative tests. The age-specific mean sojourn times and the sensitivity of the mammography were applied in the stochastic model. An optimal cost-effectiveness was determined by the incremental cost-effectiveness ratio and lifetime schedule sensitivity. Sensitivity analyses were undertaken to assess parameter uncertainty. The selected cost-effective strategies were: (1) the current biennial mammography screenings for women who are at least 40 years old; B reast cancer has become the fastest-growing cancer in Korean women due to their Westernized lifestyle, accelerated by rapid socioeconomic development.(1) A national biennial screening program including mammography for women at least 40 years of age was launched in Korea in 1996. Mammography has been used worldwide for the early detection of breast cancer since the 1980s. Many randomized controlled trial studies have shown that mammography screening for women aged between 50 and 65 years is indeed an effective tool for the early detection of breast cancer and for reduction of the breast cancer mortality rate.(4) It was also reported that a screening plan for women in their 40s or for women older than 65 years might be most cost-effective. (5,6) In recent years, there have been several debates as to whether the screening of women older than 70 years of age is cost-effective.(7) The consensus regarding a mammography screening plan in Western countries is to perform it annually or every 2 or 3 years for women who are at least 40 years old. (8) Korean women are also recommended to follow the mammography guidelines developed in the West.However, several Korean researchers have questioned whether these Western guidelines are appropriate for Korean women because the epidemiological patterns of breast cancer among Korean women are different from those in Western women, as shown in Figure 1. For example, the incidence of breast cancer among Korean women as well as other Asians is less than 50% of the breast cancer incidence in the West although the incidence rate has sharply risen in Asia.(9,10) Also, the peak incidence rate of breast cancer among Korean women has been observed in women between the ages of 45 and 49 years, whereas the incidence rate of breast cancer among women in the West has a linear relationship with age (Fig. 1). (2,(11)(12)(13)(14) A new strategy for cost...

In biomedical studies, correlated failure time data arise often. Although point and confidence interval estimation for quantiles with independent censored failure time data have been extensively studied, estimation for quantiles with correlated failure time data has not been developed. In this article, we propose a nonparametric estimation method for quantiles with correlated failure time data. We derive the asymptotic properties of the quantile estimator and propose confidence interval estimators based on the bootstrap and kernel smoothing methods. Simulation studies are carried out to investigate the finite sample properties of the proposed estimators. Finally, we illustrate the proposed method with a data set from a study of patients with otitis media.

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Objective To propose an efficient screening schedule for breast cancer among Korean women using the stochastic model in which the age-specific incidence rate was considered. Setting Female breast cancer data in the Korea Central Cancer Registry 2002. Methods The stochastic model was based on the threshold method, in which the schedule is determined by a pre-specified threshold value. The threshold value was defined as the probability of being in a preclinical state of breast cancer at age 40 years. The sensitivity of the mammography was specified as 0.7. Two models for mean sojourn time (MST) in the preclinical state were considered; MSTs for Model I were 2 (ageso50 years), 3 (ages 50-59 years), and 4 years (ages X60 years), and MSTs for Model II were 3, 4, and 5 years for the corresponding age groups. Results The threshold method for Model I generated 19 examinations within the screening ages of 40-69 years. Each screening time was determined at ages 40.0, 41.6, 43.2, 44.8, 46.0, 47.2, 48.4, 49.6, 50.7, 51.7, 52.7, 53.7, 54.7, 56.2, 57.8, 59.4, 61.3, 63.1, and 64.9 years. The schedule sensitivity of Model I was 64.2%, which was higher than that (57.5%) of the biennial periodic schedule. Model II included 11 screenings between the ages of 40 and 69 years and also showed a higher schedule sensitivity, especially for women aged 40 years as compared with the biennial screening. Conclusions This finding suggests that the threshold screening schedule for breast cancer increase the schedule sensitivity by reflecting the age-specific incidence rate of a population.

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