Methods ELCAP has enrolled 1000 symptom-free volunteers, aged 60 years or older, with at least 10 pack years of cigarette smoking and no previous cancer, who were medically fit to undergo thoracic surgery. After a structured interview and informed consent, chest radiographs and low-dose CT were done for each participant. The diagnostic investigation of screen-detected non-calcified pulmonary nodules was guided by ELCAP recommendations, which included short-term high-resolution CT follow-up for the smallest non-calcified nodules.

Findings Non-calcified nodules were detected in 233 (23% [95%; CI 21-26]) participants by low-dose CT at baseline, compared with 68 (7% [5-9]) by chest radiography. Malignant disease was detected in 27 (2.7% [1.8-3.8]) by CT and seven (0.7% [0.3-1.3]) by chest radiography, and stage malignant disease in 23 (2.3% [1.5-3.3]) and four (0.4% [0.1-0.9]), respectively. Of the 27 CT-detected cancers, 26 were resectable. Biopsies were done on 28 of the 233 participants with non-calcified nodules; 27 had malignant non-calcified nodules and one had a benign nodule. Another three individuals underwent biopsy against the ELCAP recommendations; all had benign non-calcified nodules. No participant had thoracotomy for a benign nodule.

Interpretation low-dose CT can greatly improve the likelihood of detection of small non-calcified nodules, and thus of lung cancer at an earlier and potentially more curable stage. Although false-positive CT results are common. they can be managed with little use of invasive diagnostic procedures.