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Journal ArticleDOI

Estimating Sensitivity and Sojourn Time in Screening for Colorectal Cancer A Comparison of Statistical Approaches

15 Sep 1998-American Journal of Epidemiology (Oxford University Press)-Vol. 148, Iss: 6, pp 609-619
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.

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Citations
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Journal ArticleDOI
TL;DR: A smoothing procedure is incorporated that produces a realistic g function while still closely reproducing the original incidence function I upon convolution with f, which results in more accurate estimates of sojourn time and lead time and allows for estimation of quantities related to overdiagnosis.
Abstract: The model that specifies that cancer incidence, I, is the convolution of the preclinical incidence, g, and the density of time in the preclinical phase, f, has frequently been utilized to model data from cancer screening trials and to estimate such quantities as sojourn time, lead time, and sensitivity. When this model is fit to the above data, the parameters of f as well as the parameter(s) governing screening sensitivity must be estimated. Previously, g was either assumed to be equal to clinical incidence or assumed to be a constant or exponential function that also had to be estimated. Here we assume that the underlying incidence, I, in the study population (in the absence of screening) is known. With I known, g then becomes a function of f, which can be solved for using (numerical) deconvolution, thus eliminating the need to estimate g or make assumptions about it. Since numerical deconvolution procedures may be highly unstable, however, we incorporate a smoothing procedure that produces a realistic g function while still closely reproducing the original incidence function I upon convolution with f. We have also added the concept of competing mortality to the convolution model. This, along with the realistic preclinical incidence function described above, results in more accurate estimates of sojourn time and lead time and allows for estimation of quantities related to overdiagnosis, which we define here.

22 citations

Journal ArticleDOI
TL;DR: Continuous frailty and discrete mover—stayer models were developed and results were compared with those of purely homogeneous models in a previous study in terms of cumulative risk of malignant transformation from adenoma to invasive colorectal cancer.
Abstract: Homogeneous multi-state models of disease progression have been widely used for designing and evaluating cancer screening programs. However, in screening for premalignant conditions of the cervix or large bowel, it is unlikely that all premalignant lesions have the same underlying propensity for progression. Incorporating frailty into multi-state models raises practical difficulties as it precludes the derivation of finite transition probabilities by matrix solution of the Kolmogorov equations. We address this problem by formulating a heterogeneous process as a series of homogeneous processes linked by transitions which are subject to heterogeneity (frailty). Continuous frailty and discrete mover-stayer models were developed. We applied these to the example of progression of adenoma to colorectal cancer in a three-state model and to a five-state model including consideration of adenoma size. Results were compared with those of purely homogeneous models in a previous study in terms of cumulative risk of malignant transformation from adenoma to invasive colorectal cancer.

22 citations

Journal ArticleDOI
TL;DR: A flexible decision‐making framework for the design of early detection programs is described, and the choice of timing when each individual in the screening program is examined only once is investigated, as well as derive closed‐form solutions of the optimal age using two specifications of utility functions.
Abstract: L'efficacite des strategies de depistage des maladies depend pour beaucoup du moment ou l'on procede aux tests et aux examens qui peuvent permettre de les diagnostiquer. Dans cet article, qui voudrait definir des cadres flexibles de prise de decision pour une meilleure politique de detection, nous nous penchons sur le choix du moment ou proceder au depistage dans le cas ou celui-ci n'est applique a chaque personne qu'a une seule reprise. Pour ce faire, nous nous concentrons sur la relation theorique entre le moment optimal de l'examen et les distributions des temps passes par les patients dans differentes categories d'etats de sante relatifs a la maladie, puis nous derivons, a partir de deux fonctions d'utilite distinctes, des solutions approchees de l'âge optimal pour le depistage. Nous discutons la maniere dont cette solution optimale est influencee par les antecedents des patients et par la specification des fonctions d'utilite. Enfin, nous presentons une application dans la detection du cancer du colon par sigmoidoscopie ou coloscopie uniques.

20 citations

Journal ArticleDOI
TL;DR: There are large numbers of cancer that are not detected through fecal occult blood test-based screening that should be emphasized to ensure that individuals with symptoms are not falsely reassured.
Abstract: Objective To analyze interval cancers among participants in a screening program for colorectal cancer (CRC) during four screening rounds Methods The study population consisted of participants of a fecal occult blood test-based screening program from February 2000 to September 2010, with a 30-month follow-up (n = 30,480) We used hospital administration data to identify CRC An interval cancer was defined as an invasive cancer diagnosed within 30 months of a negative screening result and before the next recommended examination Gender, age, stage, and site distribution of interval cancers were compared with those in the screen-detected group Results Within the study period, 97 tumors were screen-detected and 74 tumors were diagnosed after a negative screening In addition, 17 CRC (183%) were found after an inconclusive result and 2 cases were diagnosed within the surveillance interval (21%) There was an increase of interval cancers over the four rounds (from 324% to 460%) When compared with screen-detected cancers, interval cancers were found predominantly in the rectum (OR: 366; 95% CI: 151–888) and at more advanced stages (P = 0025) Conclusion There are large numbers of cancer that are not detected through fecal occult blood test-based screening The low sensitivity should be emphasized to ensure that individuals with symptoms are not falsely reassured

19 citations


Cites background from "Estimating Sensitivity and Sojourn ..."

  • ...The relationship between benefits and risks depends on the quality of screening [6, 7]....

    [...]

Journal ArticleDOI
TL;DR: It is found that the mean sojourn time for males is much longer than that for females, which may imply that FOBT screening for colorectal cancer may be more effective for males than for females.
Abstract: Objectives The association between screening sensitivity, transition probability, and individual’s age in FOBT for colorectal cancer are explored, for both males and females.

16 citations


Cites methods from "Estimating Sensitivity and Sojourn ..."

  • ...[7] estimated the sensitivity and the mean sojourn time in fecal Hemoccult testing, using data from Calvados, France, between 1991 and 1994....

    [...]

References
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Journal ArticleDOI
TL;DR: The focus is on applied inference for Bayesian posterior distributions in real problems, which often tend toward normal- ity after transformations and marginalization, and the results are derived as normal-theory approximations to exact Bayesian inference, conditional on the observed simulations.
Abstract: The Gibbs sampler, the algorithm of Metropolis and similar iterative simulation methods are potentially very helpful for summarizing multivariate distributions. Used naively, however, iterative simulation can give misleading answers. Our methods are simple and generally applicable to the output of any iterative simulation; they are designed for researchers primarily interested in the science underlying the data and models they are analyzing, rather than for researchers interested in the probability theory underlying the iterative simulations themselves. Our recommended strategy is to use several independent sequences, with starting points sampled from an overdispersed distribution. At each step of the iterative simulation, we obtain, for each univariate estimand of interest, a distributional estimate and an estimate of how much sharper the distributional estimate might become if the simulations were continued indefinitely. Because our focus is on applied inference for Bayesian posterior distributions in real problems, which often tend toward normality after transformations and marginalization, we derive our results as normal-theory approximations to exact Bayesian inference, conditional on the observed simulations. The methods are illustrated on a random-effects mixture model applied to experimental measurements of reaction times of normal and schizophrenic patients.

13,884 citations

Journal ArticleDOI
TL;DR: In this paper, three sampling-based approaches, namely stochastic substitution, the Gibbs sampler, and the sampling-importance-resampling algorithm, are compared and contrasted in relation to various joint probability structures frequently encountered in applications.
Abstract: Stochastic substitution, the Gibbs sampler, and the sampling-importance-resampling algorithm can be viewed as three alternative sampling- (or Monte Carlo-) based approaches to the calculation of numerical estimates of marginal probability distributions. The three approaches will be reviewed, compared, and contrasted in relation to various joint probability structures frequently encountered in applications. In particular, the relevance of the approaches to calculating Bayesian posterior densities for a variety of structured models will be discussed and illustrated.

6,294 citations

Journal Article
TL;DR: Stochastic substitution, the Gibbs sampler, and the sampling-importance-resampling algorithm can be viewed as three alternative sampling- (or Monte Carlo-) based approaches to the calculation of numerical estimates of marginal probability distributions.
Abstract: Stochastic substitution, the Gibbs sampler, and the sampling-importance-resampling algorithm can be viewed as three alternative sampling- (or Monte Carlo-) based approaches to the calculation of numerical estimates of marginal probability distributions. The three approaches will be reviewed, compared, and contrasted in relation to various joint probability structures frequently encountered in applications. In particular, the relevance of the approaches to calculating Bayesian posterior densities for a variety of structured models will be discussed and illustrated.

6,223 citations

Book
01 Jan 1996
TL;DR: Mathematica has defined the state of the art in technical computing for over a decade, and has become a standard in many of the world's leading companies and universities as discussed by the authors.
Abstract: From the Publisher: Mathematica has defined the state of the art in technical computing for over a decade, and has become a standard in many of the world's leading companies and universities From simple calculator operations to large-scale programming and the preparation of interactive documents, Mathematica is the tool of choice

3,566 citations

01 Jan 1996
TL;DR: From the Publisher: Mathematica has defined the state of the art in technical computing for over a decade, and has become a standard in many of the world's leading companies and universities.
Abstract: From the Publisher: Mathematica has defined the state of the art in technical computing for over a decade, and has become a standard in many of the world's leading companies and universities. From simple calculator operations to large-scale programming and the preparation of interactive documents, Mathematica is the tool of choice.

3,115 citations