Lead time distribution for individuals with a screening history

Abstract

We derived the distribution of lead time for periodic screening in the future when an individual has a screening history with negative results. It is a mixture of a point mass at zero and a positive sub-PDF. The motivation comes from the reality that for people in older age, they may already have some screening exams for targeted cancer before and still look healthy and are asymptomatic at their current age. How to evaluate their future screening result is a challenge. We explored how the screening history would affect the lead time if one would be diagnosed with cancer in the future. Simulations were carried out on combinations of different initial screening age, current age, sensitivity, mean sojourn time, and screening schedule in the past and in the future. The method developed can be applied to periodic exams for any kind of chronic disease, such as cancer. We applied our new method of evaluating the lead time distribution for male and female heavy smokers using low-dose computed tomography in the National Lung Screening Trial.