Objectives: This study is to identify an optimal cut-off for two-stage breast cancer screening making allowance for variation of the baseline incidence rate and utility values between sensitivity and specificity.
Methods: We used data from a two-stage breast cancer screening of Taiwanese women aged 50-69 years for whom risk stratification was based on a composite risk score (conventional risk factors); subjects with a risk score greater than the cut-off score were screened using mammography. The Bayesian posterior risk for breast cancer was computed by incorporation of the baseline incidence rate and the risk score. Bayes' maximum utility decision rule was then developed to determine the optimal screening cut-off.
Results: With a risk score of -9 applied to the current two-stage breast cancer screening programme, we could detect one breast cancer case for every 1406 women. Given different predetermined risks, the selected cut-offs were -9 for 1:1200, -8 for 1:800, -4 for 1:600, -1 for 1:400 and 3 for 1:200 for women aged 50-59 years. When the regret utility ratio of positive predictive value to negative predictive value was set at 1:10, the specificity and sensitivity were 58.5% and 70.4%, respectively, and the optimal cut-off was -5.5. When the ratio was set at 10:1, the sensitivity and specificity were 75.5% and 57.1%, respectively, and the optimal cut-off value was -7.5.
Conclusions: This study demonstrates that Bayes' maximum utility decision rule can be used to determine optimal cut-off values for two-stage breast cancer screening in countries or areas with lower or intermediate incidence of breast cancer.
© 2010 Blackwell Publishing Ltd.