An updated and modified lung-cancer risk-prediction model developed from the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial “was more sensitive” for lung cancer detection than criteria from the National Lung Cancer Screening Trial (NLST), according to a study in TheNew England Journal of Medicine. Compared with NLST standards, criteria for the new model, known as PLCOM2012, “had improved sensitivity (83.0% vs 71.1%, P < .001) and positive predictive value (4.0% vs 3.4%, P = .01), without loss of specificity (62.9% and. 62.7%, respectively; P = .54); 41.3% fewer lung cancers were missed,” the researchers reported.
The NLST criteria include an age between 55 and 74 years, a history of smoking of at least 30 pack-years, and less than 15 years since cessation of smoking. “These selection criteria were intended to increase the yield of lung cancers, but they exclude many known risk factors for lung cancer,” the researchers noted. Additional criteria were included in the lung-cancer risk-prediction model the investigators previously developed and validated involving former and current smokers in PLCO control and intervention groups.
“Model predictors included age, level of education, body mass index, family history of lung cancer, chronic obstructive pulmonary disease, chest radiography in the previous 3 years, smoking status (current smoker vs former smoker), history of cigarette smoking in pack-years, duration of smoking, and quit time (the number of years since the person quit smoking),” the researchers reported.
While the NLST model “has high predictive discrimination,” it “can be cumbersome to apply because it uses complicated modeling procedures” and “may benefit from the inclusion of additional predictors,” the authors noted. In addition, the model based risks on a median follow-up of 9.2 years, “which exceeds the follow-up in the NLST and makes estimates inaccurate when applied to the NLST.” Among the aims of the current study were to modify and update the PLCO model and make it apply directly to NLST data.
PLCOM2012, was developed and validated with data from the 80,375 persons in the PLCO control and intervention groups who had ever smoked. “In the validation data set, 14,144 of 37,332 persons (37.9%) met NLST criteria. For comparison, 14,144 highest-risk persons were considered positive (eligible for screening) according to PLCOM2012 criteria. We compared the accuracy of PLCOM2012 criteria with NLST criteria to detect lung cancer,” the researchers explained.
“Among 37,332 smokers in the PLCO intervention group, the PLCOM2012 selected 81 more persons for screening who received a diagnosis of lung cancer in follow-up than did the NLST criteria. If one assumes a 15% rate of overdiagnosis, then 69 of these persons can be considered to have ‘true’ life-threatening lung cancer,” the authors reported.
“In conclusion, the PLCOM2012 predicted the 6-year risk of lung cancer with high accuracy and was more efficient at identifying persons for lung cancer screening, as compared with the NLST criteria,” the authors stated. “Because the mortality reduction from CT screening effectiveness did not vary according to lung-cancer risk, it appears that use of the PLCOM2012 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.” ■
Tammemägi MC, et al: N Engl J Med 368:728-736, 2013.