Reductions in lung cancer mortality with low-dose CT screening vs. chest X-ray among participants in the National Lung Screening Trial have been sustained over extended follow-up, according to results of an updated analysis of the trial published in Journal of Thoracic Oncology.
The number of patients needed to screen to prevent one lung cancer death also appeared similar to that of the original report, published in 2011.
“Lung cancer is the leading cause of cancer death worldwide, and early detection and treatment through screening with low-dose CT has been investigated as a potential means of reducing lung cancer deaths for more than 2 decades,” Paul F. Pinsky, PhD, chief of the early detection research branch at NCI, said in a press release. “This study adds further weight to the notion that CT screening is effective.”
The National Lung Screening Trial randomly assigned high-risk current and former smokers to three annual screenings with low-dose CT (n = 26,722; 59% men) or chest X-rays (n = 26,730; 59% men).
Previous results after median follow-up of 6.5 years showed a significant 20% decrease in lung cancer deaths with low-dose CT than with chest X-ray. These results served as the basis for the U.S. Preventive Task Force recommendation in 2013 that individuals who meet certain age and smoking history criteria undergo annual screening with low-dose CT.
The analysis by Pinsky and colleagues extended median follow-up to 11.3 years for lung cancer incidence and 12.3 years for mortality.
Results showed 1,701 lung cancers diagnosed in the low-dose CT group and 1,681 diagnosed in the chest X-ray group (RR = 1.01; 95% CI, 0.95-1.09).
Researchers observed fewer stage IV cases in the low-dose CT group than in chest X-ray group (468 vs. 579; RR = 0.79; 95% CI, 0.7-0.89).
Among those diagnosed, 1,147 patients in the low-dose CT group and 1,236 patients in the chest X-ray group died of lung cancer (RR = 0.92; 95% CI, 0.85-1).
The differences across groups in the number of deaths due to lung cancer per 1,000 patients was 3.3, meaning 303 patients would need to be screened to prevent one lung cancer death. The original estimate was 320 patients.
“The stability of this difference over time indicates that low-dose CT screening did not just delay lung cancer death by a few years, but prevented it, or at least delayed it for more than a decade,” the researchers wrote.
An analysis adjusted for dilution and including only deaths with diagnosis through study year 6 (578 in low-dose CT group vs. 646 in chest X-ray group) showed a lung cancer mortality RR of 0.89 (95% CI, 0.8-0.997).
A lack of information on use of low-dose CT screening after the original trial period served as the study’s primary limitation.
“National Lung Screening Trial participants were sent a letter in 2010 summarizing trial results, with subjects [in the chest X-ray group] told that they may want to discuss low-dose CT screening with their health care provider and subjects [in the low-dose CT group] told they may want to discuss continuing screening,” Pinsky and colleagues wrote. “However, low-dose CT screening was not generally covered by private insurance or Medicare until 2015, and survey evidence suggests that usage was low in the U.S. through 2015.” – by John DeRosier
Disclosures: Pinsky reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.