LAUSR

Lengthening the annual low-dose computed tomography (CT) screening interval for individuals at lowest risk of lung cancer could reduce harms and improve efficiency. We analyzed 23,328 participants in the National Lung Screening Trial who had a negative CT screen (no ≥ 4mm nodules) to develop an individualized model for lung-cancer risk after a negative CT. The Lung Cancer Risk Assessment Tool + CT (LCRAT+CT) updates "pre-screening risk" (calculated using traditional risk factors) with selected CT features. At the next annual screen following a negative CT, risk of cancer detection was reduced among the 70% of participants with neither CT-detected emphysema nor consolidation (median-risk=0.2%, IQR=0.1%-0.3%). However, risk increased for the 30% with CT-emphysema (median-risk=0.5%, IQR=0.3%-0.8%) and the 0.6% with consolidation (median=1.6%, IQR=1.0%-2.5%). As one example, a threshold of next-screen risk below 0.3% would lengthen the interval for 57.8% of screen-negatives, thus averting 49.8% of next-screen false-positives among screen-negatives but delaying diagnosis for 23.9% of cancers. Our results support that many, but not all, screen-negatives might reasonably lengthen their CT screening interval.