Initial LDCT appearance of incident lung cancers in the ITALUNG trial

Objectives: To characterize early features of lung cancers detected with low-dose computed tomography (LDCT) screening.Materials and methods: Two radiologists reviewed prior LDCTs in 20 incident cancers diagnosed at annua lrepeat screening rounds and 83 benign nodules observed in the ITALUNG trial.Results: No abnormality was observed in 3 cancers. Focal abnormalities in prior LDCT were identifiedi n 17(85%) cancers (14 adenocarcinomas; 14 stage I). Initial abnormalities were intra-pulmonary in 10,sub pleural in 4 and perifissural in 3. Average mean diameter was 9 mm (range 4.5–18 mm). Nine exhibitedsolid, 4 part-solid and 4 non-solid density. The margins were smooth and regular in 5 cases, lobulated in6, irregular with spiculations in 3 and blurred in 3. Ten (59%) initial focal abnormalities had a round oroval nodular shape, but 7(41%) had a non-nodular complex (n = 5) or “stripe-like” (n = 2) shape. Bronchus sign was observed in 3 cases and association with cystic airspace in 2 cases. Non-solid density, complexor “stripe-like” shape, bronchus sign and association with cystic airspace had a specificity higher than90%, but positive predictive value of every feature of incident lung cancers was low (range 10.4–50%).Conclusions: The vast majority of cancers diagnosed at annual repeat show corresponding focal lungabnormalities in prior LDCTs. Perifissural location and non-nodular shape do not exclude the possibilityof early lung cancer. Since specificity of the early features of incident lung cancer is incomplete and theirpositive predictive value is low, all focal pulmonary abnormalities detected in screened subjects shouldbe re-evaluated in subsequent LDCTs.