Modified criteria for screening current or former smokers for lung cancer appeared to be more accurate than currently recommended criteria.
In a post hoc statistical analysis of data on 28,288 people, a version of the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial criteria identified 81 more lung cancers and would have saved an additional 12 lives over a 6-year period, compared with the National Lung Screening Trial (NLST) criteria, Martin C. Tammemägi, Ph.D., and his associates reported.
Dr. Martin C. Tammemagi
The modified PLCO criteria were significantly more sensitive than the NLST criteria (83% vs. 71%, respectively) and had a better positive predictive value (4% vs. 3.4%) with no loss of specificity (62% each). Use of the PLCO criteria would have missed 41% fewer cancers, reported Dr. Tammemägi of Brock University, St. Catharines, Ont. (N. Engl. J. Med. 2013;368:728-36).
The American Cancer Society and several other organizations recommend using the NLST criteria, or a version of the criteria, to identify people at high risk of lung cancer who might benefit from screening with low-dose CT imaging. Using the NLST criteria would reduce deaths from lung cancer by 20% (N. Engl. J. Med. 2011;365:395-409). Risk factors include an age between 55 and 74 years, at least a 30 pack-year history of smoking, and no more than 15 years since quitting smoking.
The PLCO criteria added risk factors excluded in the NLST, such as education level (as a proxy for socioeconomic status); body mass index; a family history of lung cancer; chronic obstructive pulmonary disease; chest x-ray within the last 3 years; and not only a history of smoking in pack-years but also the duration of smoking. The PLCO model can be cumbersome to apply because it uses complicated modeling procedures. A spreadsheet for calculating the 6-year risk for lung cancer in a current or former smoker using the PLCO criteria in Dr. Tammemägi’s report can be downloaded here.
The PLCO trial followed patients for a median of 9 years, longer than the median 6-year follow-up in the NLST. The investigators modified the PLCO criteria so that it was directly applicable to patients in the NLST and truncated PLCO follow-up so that they could compare data on 14,144 people in each of the studies. The modified PLCO model was developed and validated using data on 80,375 people in the PLCO trial.
Among people who did not qualify for screening under PLCO criteria, 0.5% developed lung cancer, a significantly smaller proportion than the 0.85% of patients excluded from screening under NLST criteria who then developed lung cancer, Dr. Tammemägi reported. Overall, the modified PLCO criteria identified 12% more of the 678 lung cancers in the total cohort than did NLST criteria. The modified PLCO criteria missed 115 lung cancers; the NLST criteria missed 196.
In the PLCO model, current or former smokers were more likely to develop lung cancer with increasing age; black vs. white race; lower socioeconomic status; lower BMI, self-reported history of chronic obstructive pulmonary disease; family history of lung cancer; current smoking; increasing number of cigarettes smoked per day; duration of smoking; and shorter time since quitting, if no longer smoking.
Prospective studies should evaluate the modified PLCO criteria in different populations and clinical and public health settings, Dr. Tammemägi suggested. Additional risk factors may be added to the model in the future to enhance its predictive accuracy.
Dr. Tammemägi reported having no financial disclosures.