Re: Lung cancer mortality in the Mayo Lung Project: impact of extended follow-up

Chest X-ray screening for lung cancer: overdiagnosis, endpoints, and randomized population trials

Publication of the National Lung Screening Trial (NLST) generated excitement by concluding that CT screening reduces lung cancer mortality when compared to chest X-ray (CXR) screening. In contrast, CXR screening has long been considered to be ineffective. This is because randomized population trials (RPTs) have failed to demonstrate significant mortality reductions in populations randomized to CXR screening. While these studies demonstrate that CXR screening is associated with significant survival advantages, these advantages have been widely interpreted as spurious, due to the inference that CXR screening leads to substantial lung cancer overdiagnosis. Indeed, the reality of the overdiagnosis hypothesis is the only alternative to the conclusion that CXR screening was effective in these trials and that survival more accurately reflected the benefit of CXR screening than mortality. Mortality comparisons would be biased if randomization fails to create comparison groups with an equal probability of mortality from the target cancer. The objective of this manuscript is to review existing RPTs on CXR screening for lung cancer, and to analyze which endpoint most accurately reflects screening efficacy. We conclude that the evidence supports that CXR screening is superior to no screening, and the magnitude of overdiagnosis is minimal in the context of CXR screening.

An evaluation of chest X-ray screening for lung cancer in gunma prefecture, Japan: a population-based case-control study

In order to evaluate the efficacy of annual chest X-ray screening for lung cancer, a case-control study was conducted in Gunma Prefecture, Japan. Population-based annual lung cancer screening programmes have been conducted by the local government in Gunma Prefecture since the mid-1970s. A total of 121 case subjects, including 91 high-risk males and 30 non-high-risk females between the ages of 40 and 79 years who died of lung cancer from 1992 to 1997 were evaluated. A total of 536 controls (3-5 controls for each case) were matched to case subjects by gender, year of birth, address and smoking habits. Controls were selected from screening programme lists provided by the local governments. All case subjects were also included on these lists. The smoking-adjusted odds ratio (OR) of lung cancer death for those subjects screened within 12 months prior to diagnosis versus those not screened was 0.68 (95% confidence interval (CI): 0.44-1.05; P=0.084). When the analysis was conducted without matching case and control subjects by smoking habits, the OR was 0.79 (95% CI: 0.53-1.18). When stratified by histological type, the OR was 0.62 (95% CI: 0.31-1.24) for adenocarcinoma, and 1.01 (95% CI: 0.44-2.31) for squamous cell carcinoma. The results of this study suggest 20-30% of deaths attributable to lung cancer, especially adenocarcinoma, might be prevented by annual chest X-rays.

Computed tomography screening for lung cancer

The development of CT technology reopened the lung cancer screening debate. Computed tomography screening for lung cancer certainly meets all the criteria required for an appropriate screening test. First and perhaps most importantly, the disease for which the screening is being performed should have a significant prevalence in the population being studied and be a significant health risk for those afflicted with it. Lung cancer is the leading cause of cancer death in both men and women, and one of the most lethal of all cancers.

Early lung cancer action project: annual screening using single-slice helical CT

The advent of helical CT imaging held promise for the early diagnosis, and thereby, for enhanced curability of lung cancer--a highly fatal disease. In 1993, the Early Lung Cancer Action Project (ELCAP) was initiated and experimentally screened a cohort of 1,000 high-risk persons. Here we summarize the results of the baseline and annual repeat CT screening of these 1,000 subjects. CT-based screening (compared to traditional radiology) was clearly shown to enhance the detection of lung cancer at earlier and more curable stages. A discussion follows of the meaning of the results and possible future screening protocols.