Lung cancer risk after baseline round of screening: Only 20% of NLST eligibles require annual round

PURPOSE/OBJECTIVES: To calculate the risk of lung cancer (LC) in 1 year and 3 years after baseline low-dose computed tomography (LDCT) in high-risk subjects selected by the National Lung Cancer Screening Trial (NLST) criteria. METHODS AND MATERIALS: Subjects from the Multicentric Italian Lung Detection (MILD) trial were selected according to NLST criteria: age >=55 years and pack-years >=30. Baseline characteristics were: smoking status (former/current), gender, percent of predicted forced expiratory volume in first second (FEV 1% pred, 90% threshold), Tiffeneau ratio (70% threshold), nodules at baseline LDCT. The risk of LC in 1 and 3 years was calculated by multivariate models. RESULTS: In 1,248 NLST eligible screenees, LC frequency was 1.2% at 1year, 2.6% at 3 years. At 1 year, nodule volume on LDCT was the only predictor of LC risk (volume >250mm3, odds ratio (OR) 34.25, p=0.0009). At 3 years, the risk of LC was predicted by: nodule volume 113-250 mm3 (OR9.52 p=0.01), nodule volume >250mm3 (OR29.07, p<0.001), Tiffeneau <=70% (OR2.08 p=0.0195). A simulation of triennial screening rounds, with selective annual round only for nodule volume >=113mm3 (19,9% in our population) showed 40% reduction of LDTC through 3 years, and 80% LDCT saving at each annual round. CONCLUSION: Annual round is worthwhile for nodule >=113mm3 (about 20% in our population). Screening every 3 years can safely reduce the LDCT burden for nodule <113mm3 (about 80% in our population).