Uncertainty in interpretation of results from completed studies has led to conflicting positions in the medical community and confusion in populations at risk regarding the value of chest x-ray screening. Only a properly designed randomized trial can demonstrate whether an important benefit exists. To this end, the National Cancer Institute (NCI) is conducting the Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial. This is a long-term randomized controlled trial in which 37,000 men are screened for prostate, lung, and colorectal cancers and 37,000 women are screened for lung, colorectal, and ovarian cancers. The lung component uses annual posteroanterior view chest x-ray as the screening modality. Equal numbers of men and women are followed up with routine medical care as controls. In the baseline screen, 9% of participants had a positive screen, with significant increases in prevalence of positive screens with older age and more extensive smoking histories. A total of 126 participants were subsequently diagnosed with lung cancer, and approximately one-half of these were stage I.
Spiral Computed Tomography (CT)
There are intensive efforts to improve lung cancer screening with newer technologies, including low-dose helical computed tomography (LDCT) and molecular techniques.[30,31] LDCT is more sensitive than chest radiography. In the Early Lung Cancer Action Project (ELCAP) screening study, LDCT detected almost six times as many stage I lung cancers as chest radiography, and most of these tumors were no larger than 1 cm in diameter. The effectiveness of screening with LDCT has not yet been evaluated in a controlled clinical trial.
Eight ongoing observational studies of LDCT in various parts of the world have been reported and summarized. These are relatively small studies, ranging from about 600 to 8,000 participants, which began between 1992 and 2000. Most of the studies include a substantial percentage of females, and the studies in Japan include nonsmokers. Findings include a nodule or positivity rate of 5% to 51%, 0.4% to 3% lung cancers, 50% to 95% adenocarcinomas, 50% to 91% stage I or IA cancers, and estimates of sensitivity ranging from 40% to 95%.
Although the efficacy of CT screening in reducing lung cancer mortality is uncertain, CT screening has been hypothesized to have the benefit of promoting smoking cessation among current smokers. In a randomized controlled lung cancer CT screening trial in Denmark, all current smokers enrolled in the trial received a minimal smoking cessation intervention. After 1 year of follow-up, comparable quit rates were observed in the screened and unscreened groups (11.3% vs. 10.4%; P = .47). Based on evidence from a well-designed randomized controlled trial, undergoing CT screening for lung cancer appears not to be significantly associated with smoking cessation.