CHEST X-RAY AND CANCER PRECLINICAL SOJOURN TIME

Estimation of Sensitivity and Specificity of Chest X-ray and Cancer Preclinical Sojourn Time for Lung Cancer Screening Trials

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 China, 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. New method is applied to the data from the lung component of PLCO cancer screening trial and Yunnan Tin Miners Lung Cancer study in China

Table of Content

Introduction5

Assumptions, notation, and definitions14

Models Formulation16

Discussion and Conclusion25

References33

Appendix35

Estimation of Sensitivity and Specificity of Chest X-ray and Cancer Preclinical Sojourn Time for Lung Cancer Screening Trials

Introduction

Lung cancer is the leading cause of cancer death in the world. The outcomes of lung cancer was dismal, with 5-year survival around 5% in the past in China and around 15% in recent (1995—2001) USA. To date, there is no standard and acceptable screening method for a person of either normal or high risk for lung cancer, although there are several ongoing trials. Screening for lung cancer with chest X-ray (CXR) and sputum cytology has been evaluated in several randomized lung cancer screening trials. However, there was lacking of evidence on long-term mortality reduction. It is speculated on whether small benefit of screening for lung cancer is attributed to shorter mean sojourn time (MST), namely, average duration of preclinical screen-detectable phase (Thomas, 1992, 837). Studies were few, particularly in oriental people, and have been reported to have a wide range between 7—8 months and 4 years (for early stage disease). Different ethnic/racial groups may have different natural history regarding the progression of lung cancer.

In addition to genetic disparity, cigarette smoking was identified as the single most predominant cause of the lung cancer. However, cigarette smoking may only partially explain the epidemiology of lung cancer in China. Moreover, the distribution of histological type may also vary from racial group to racial group. Less is known about whether the MST for smoker is ...