Abstract
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.
Highlights
Lung cancer, the leading cause of cancer death for both men and women, occurs in the lungs and claims more lives each year than do breast, colon, and prostate and ovarian cancers combined
Let ni,t0 be the total number of individuals in this cohort examined at the i-th screening, si,t0 is the number of cases detected at the i-th screening exam, and ri,t0 is the number of cases diagnosed in the clinical state sc within the interval, which is the interval cases.For the National Lung Screening Trial (NLST) data, since the age of participants enrolled was between 55 to 74 at the study entry, the likelihood function for all groups is:
Chen et al [9] estimated the screening sensitivity of sputum cytology as a supplement to the chest X-ray using MSKC-LCSP data was 86.64%. Compared with these previous results, the sensitivity estimated in this study was around 95% for all the groups, which is much larger. This confirms that computed tomography (CT) scan improves the lung cancer screening sensitivity compares to X-rays
Summary
The leading cause of cancer death for both men and women, occurs in the lungs and claims more lives each year than do breast, colon, and prostate and ovarian cancers combined. Smoking is the major risk factor for development of lung cancer. The general prognosis of lung cancer is poor because symptoms tend not to show up until it is at an advanced stage. Five-year survival is 54.8% for stage I lung cancer, but only 4.2% in advanced, inoperable lung cancer [2]. Since the survival rate for advanced lung cancer is low, early detection and treatment hopefully will lead to a better prognosis. Cancer screening for individuals at high risk has the potential to dramatically improve lung cancer survival rates by finding the disease at an earlier, more treatable stage. In August of 2011, the National Cancer Institute released results from its National Lung Screening Trial (NLST), a randomized clinical trial that screened at-risk smokers with either low-dose helical computed tomography (CT) or single-view chest radiography (X-ray). The final results showed a 20% reduction in lung cancer mortality in the CT arm relative to the X-ray arm
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