- CT screening for lung cancer could reap limited benefits
Caren B. Les
A study on the effectiveness of helical computed tomography (CT) screening for lung cancer has shown that the imaging technique may reduce the number of lung cancer deaths among heavy smokers but that it won’t safeguard them from other smoking-related diseases, such as other cancers, or from respiratory or heart disease.
Model-predicted lung cancer cases that are detected in the first five years (per 1000 participants) after simulated randomization are stratified according to trial group. In contrast with the control group, the screened group yielded a higher number of nonsmall-cell lung cancers (NSCLCs), the highest proportion of which is stage 1. The distribution of limited stage (LS) versus extensive stage (ES) was not significantly changed with screening. Reprinted with permission of Radiology.
Lung cancer causes more deaths in the US annually than breast, prostate and colon cancers combined, according to the Centers for Disease Control and Prevention in Atlanta. Because the smoking habit is known to cause more than 80 percent of lung cancers, current and former cigarette smokers represent an identifiable group at increased risk for the disease.
A 2006 study shows that 80 percent of patients whose lung cancers were detected using CT screening and whose cancers were surgically resected achieved a 10-year survival rate. In smokers who are not screened, malignancy typically is detected at a later stage, and survival rates are significantly lower. Aspects such as these indicate that mass screening for lung cancer could be beneficial.
Pamela M. McMahon, senior scientist at Massachusetts General Hospital and an instructor in radiology at Harvard Medical School, both in Boston, and researchers at Harvard Medical School and at the Mayo Clinic in Rochester, Minn., have studied the long-term usefulness of CT screening for lung cancer.
They entered data acquired from the Mayo Clinic’s helical CT screening study of 1520 current and former smokers into their carefully developed Lung Cancer Policy Model, a simulation model of lung cancer development, progression, detection, treatment results and survival. Using the computer model allowed them to extrapolate from existing data while waiting for long-term randomized clinical trials to be completed.
The model predicted diagnosed cases of lung cancers and deaths based on the simulated study of five annual screening examinations versus no screenings. A six-year follow-up showed that patients in the screening component had an estimated 37 percent relative increase in lung cancer detection compared with the control arm. The relative reduction in lung cancer-specific mortality was 28 percent, and reduction in all causes of mortality, 4 percent. A 15-year follow-up showed relative reduction in lung cancer-specific mortality at 15 percent and all-cause mortality at just 2 percent.
The researchers noted that CT screening could play a role in the routine health care of heavy smokers. Among their recommendations, they suggest an analysis of the cost-effectiveness of image-based screening in relation to other interventions, such as improved treatments or smoking-cessation programs.
Radiology, July 2008, pp. 278-287.
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