In this study cancer screening likelihood method was used to analyze the CT scan group in the National Lung
Screening Trial (NLST) data. Three key parameters: screening sensitivity, transition probability density from disease
free to preclinical state, and sojourn time in the preclinical state, were estimated using Bayesian approach and Markov
Chain Monte Carlo simulations. The sensitivity for lung cancer screening using CT scan is high; it does not depend on
a patient’s age, and is slightly higher in females than in males. The transition probability from the disease-free to the
preclinical state has a peak around age 70 for both genders, which agrees with the fact that the highest lung cancer
incidence rate appears between age 65 and 74. The posterior mean sojourn time is around 1.5 years for all groups, and
that explains why screening only have a short time interval to catch lung cancer. Accurate estimation of the three key
parameters is critical for other estimations such as lead time and over-diagnosis, because these quantities are functions of the three key parameters.