Recommendations on screening for lung cancer

• Published in: Canadian Medical Association journal (CMAJ) 2016-04, Vol.188 (6), p.425-432
• Format: Article
• Language: English
• Subjects: Canada - epidemiology; Canadians; Cancer screening; Care and treatment; Diagnosis; Early Detection of Cancer - standards; Guidelines; Guidelines as Topic; Humans; Lung cancer; Lung Neoplasms - diagnosis; Lung Neoplasms - epidemiology; Mass Screening - standards; Medical diagnosis; Medical screening; Methods; Morbidity - trends; Prevention; Risk; Smoking; Systematic review
• ISSN: 0820-3946; 1488-2329
• DOI: 10.1503/cmaj.151421

The systematic review performed for the task force included 33 studies on lung cancer screening; 13 RCTs studied the benefits of screening.12 Seven low-quality studies evaluated screening with chest radiography (with or without sputum cytology), compared with no screening or less intensive screening (e.g., screening with chest radiography at longer intervals or advice to have a chest radiograph) and found small benefits in terms of early disease detection. Screening with chest radiography detected more early-stage and fewer late-stage lung cancers compared with groups receiving usual care. However, such screening did not reduce lung cancer specific mortality (risk ratio [RR] 0.99, 95% confidence interval [CI] 0.92-1.07]) or all-cause mortality (RR 0.98, 95% CI 0.96-1.00) when compared with usual care.12 Two studies were found that compared lowdose CT to chest radiography. Although screening with chest radiography is not considered standard care in Canada, these studies were included in the evidence review because prior studies had shown no differences in mortality outcomes between chest radiography and usual care. One of the studies included mortality outcomes (National Lung Screening Trial).6 The National Lung Screening Trial (a high-quality RCT) reported a 15% reduction in lung cancer mortality (RR 0.85, 95% CI 0.75-0.96) and a 6% reduction in all-cause mortality (RR 0.94, 95% CI 0.88-1.00) associated with screening with low-dose CT compared with chest radiography after 6.5 years of follow-up.16 This means that screening 1000 people with lowdose CT three times at one-year intervals prevents three deaths from lung cancer compared with screening with chest radiography (number needed to screen = 322). Screening with lowdose CT reduced the absolute risk of lung cancer mortality by 0.31% and of all-cause mortality by 0.46%.12 Low-dose CT also detected significantly more cases of early-stage lung cancer (8 more per 1000 people screened) and significantly fewer cases of late-stage lung cancer (4 fewer per 1000 people screened) compared with chest radiography. Results from the second study17 comparing low-dose CT and chest radiography were not pooled with results of the National Lung Screening Trial in the systematic review because of an incompatible follow-up period (≤ 12 mo), the small number of reported events (lung cancers) and no reporting of mortality outcomes.12 The findings of the National Lung Screening Trial6 suggest that screening with low-dose CT may