Estimating Sensitivity and Sojourn Time in Screening for Colorectal Cancer A Comparison of Statistical Approaches
TL;DR: Various analytic strategies for fitting exponential models to data from a screening program for colorectal cancer conducted in Calvados, France, between 1991 and 1994 are considered, yielding estimates of mean sojourn time and sensitivity.
Abstract: The effectiveness of cancer screening depends crucially on two elements: the sojourn time (that is, the duration of the preclinical screen-detectable period) and the sensitivity of the screening test. Previous literature on methods of estimating mean sojourn time and sensitivity has largely concentrated on breast cancer screening. Screening for colorectal cancer has been shown to be effective in randomized trials, but there is little literature on the estimation of sojourn time and sensitivity. It would be interesting to demonstrate whether methods commonly used in breast cancer screening could be used in colorectal cancer screening. In this paper, the authors consider various analytic strategies for fitting exponential models to data from a screening program for colorectal cancer conducted in Calvados, France, between 1991 and 1994. The models yielded estimates of mean sojourn time of approximately 2 years for 45- to 54-year-olds, 3 years for 55- to 64-year-olds, and 6 years for 65- to 74-year-olds. Estimates of sensitivity were approximately 75%, 50%, and 40% for persons aged 45-54, 55-64, and 65-74 years, respectively. There is room for improvement in all models in terms of goodness of fit, particularly for the first year after screening, but results from randomized trials indicate that the sensitivity estimates are roughly correct. Am J Epidemiol 1998;148:609-19.
Cites background or methods or result from "Estimating Sensitivity and Sojourn ..."
...To make the results comparable with estimates provided in previous studies [5,12-15], all cases of ductal carcinoma in situ (DCIS) – a noninvasive form of breast tumor – were included....
...time unit (month) without screening – to simplify calculations, the rate is assumed constant over time as in the earlier used Markov model [5,12], probably giving a good approximation in the limited time span used in the estimation – and , i f gs , is the probability that a clinical...
...Overall, sensitivity investigations indicate that the new model is probably less vulnerable to several potential biases than the Markov model [5,12], possibly as a result of more utilized data....
...Generally, this model combines many of the advantages of the large population-based Markov methods [5,12], with more specific tumor growth estimates found in clinical studies of overlooked cancers....
...These studies  are usually analyzed using Markov models [5,6], where the mean time for a breast cancer tumor to growth from screening-detectable size to clinical detection without screening – the so-called mean sojourn time – and the STS are estimated....
Cites methods from "Estimating Sensitivity and Sojourn ..."
...This study was aimed at accurately estimating the lead time affecting semiannual and annual surveillance for HCC through a rigorous mathematical model already proposed in other cancer screening programs [15-16]....
...This distribution was used to calculate the transition rate to symptomatic disease and lead time, using the appropriate formula (equation 4) [15,16,19]....
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