Background: Indeterminate noncalcified lung nodules are a frequent finding when low-dose computed tomography (LD-CT) is used for lung cancer screening. The best clinical management for such nodules remains uncertain. We present results using positron tomography scanning (CT-PET) to evaluate LD-CT-detected lung nodules during the first year of the Continuing Observation of Smoking Subjects (COSMOS) early detection trial for lung cancer.
Methods: A total of 5200 asymptomatic current or former smokers (> or = 20 pack-years) older than 50 years of age were enrolled in a single-institution screening trial using annual LD-CT. Growing nodules and those with a maximum diameter exceeding 8 mm were studied with CT-PET. Transthoracic needle biopsy was not a routine part of the protocol.
Results: During the first year of study, 157 subjects underwent CT-PET, 66 of whom underwent surgical biopsy. Of the 58 lung cancers found on surgical biopsy, 51 were positive (standard uptake value > 2.0) and seven were negative for malignancy by CT-PET. Sensitivity was 88% overall, but 100% in the subgroup with solid nodules of 10 mm or more. Among the 8 patients with benign disease at surgical biopsy, CT-PET was positive in 6 and negative in 2.
Conclusions: CT-PET is a highly promising modality for identifying potentially malignant lesions in screening-detected lung nodules and appears particularly useful as an alternative, in the screening setting, to invasive procedures for the further investigation of uncertain nodules. Our findings also indicate that the standard uptake value threshold for positivity should be lowered for small nodules (< 10 mm). Longer follow-up and larger prospective studies are necessary to confirm these preliminary findings.