Refining the selection criteria for lung cancer screening can improve the sensitivity of screening without losing specificity, according to a new study. Lung cancer screening remains controversial, and improving the criteria could make cost-benefit analyses more attractive in general and help avoid additional deaths from lung cancer.
The National Lung Screening Trial (NLST) had previously shown a 20% reduction in mortality from lung cancer, with a computed tomography screening program. Recommendations to implement lung cancer screening are subsequently based upon the NLST guidelines, which include screening criteria of ages between 55 and 74 years, at least 30 pack-years of smoking history, and a period of less than 15 years since quitting smoking.
“These selection criteria were intended to increase the yield of lung cancers, but they exclude many known risk factors for lung cancer, and with dichotomization of continuous data, much valuable information is not included,” wrote researchers led by Martin C. Tammemägi, PhD, of Brock University in St. Catharines, Canada. A new study used additional criteria based on the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial to improve lung screening; results were published in the New England Journal of Medicine.
The study compared screening criteria in 73,618 smokers in the PLCO study and 51,033 NLST participants. The PLCO model added factors, including level of education, body mass index, family history of lung cancer, chronic obstructive pulmonary disease, chest radiography in the previous 3 years, and more specific smoking variables. Investigators found first that treating smoking intensity as a nonlinear variable, as well as adding personal history of cancer, or race or ethnic group, improved the risk prediction model by small but meaningful amounts.
Among patients who received a diagnosis of lung cancer, the sensitivity of NLST criteria was 71.1% vs 83% for PLCO criteria (P < .001). This improvement in sensitivity did not come at the cost of specificity, at 62.7% for NLST and 62.9% for PLCO criteria (P = .54). The PLCO model also fared better with regard to those excluded from screening: 0.5% of those excluded developed lung cancer, compared with 0.85% of those excluded based on NLST criteria (P < .001). PLCO criteria identified 81 more of 678 total lung cancers than the NLST criteria did.
“The wide gap in the ability to predict lung cancers between the NLST and PLCO criteria should translate into more efficient selection for screening (a higher number of cancers detected per number of persons screened), greater cost-effectiveness, and additional lives saved from low-dose CT screening,” the researchers wrote. “Because the mortality reduction from CT screening effectiveness did not vary according to lung cancer risk, it appears that use of the PLCO criteria to select persons for lung screening programs could potentially be an effective method, leading to improved cost-effectiveness of screening with additional deaths from lung cancer prevented.”