• Postdoctoral Research Fellow, Departments of Biomedical Data Science and Department of Radiology, Stanford University, Stanford, California.
• Research Assistant, Department of Biomedical Data Science, Stanford University, Stanford, California.
• Professor, Department of Radiology, Stanford University, Stanford, California.
• Departments of Biomedical Data Science and Department of Radiology, Stanford University, Stanford, California. Electronic address: sylvia.plevritis@stanford.edu.

PURPOSE: The ACR developed the Lung CT Screening Reporting and Data System (Lung-RADS) to standardize the diagnostic follow-up of suspicious screening findings. A retrospective analysis showed that Lung-RADS would have reduced the false-positive rate in the National Lung Screening Trial, but the optimal timing of follow-up examinations has not been established. In this study, we assess the effectiveness of alternative diagnostic follow-up intervals on lung cancer screening.

METHODS: We used the Lung Cancer Outcome Simulator to estimate population-level outcomes of alternative diagnostic follow-up intervals for Lung-RADS categories 3 and 4A. The Lung Cancer Outcome Simulator is a microsimulation model developed within the Cancer Intervention and Surveillance Modeling Network Consortium to evaluate outcomes of national screening guidelines. Here, among the evaluated outcomes are percentage of mortality reduction, screens performed, lung cancer deaths averted, screen-detected cases, and average number of screens and follow-ups per death averted.

RESULTS: The recommended 3-month follow-up interval for Lung-RADS category 4A is optimal. However, for Lung-RADS category 3, a 5-month, instead of the recommended 6-month, follow-up interval yielded higher mortality reduction (0.08% for men versus 0.05% for women), and higher number of deaths averted (36 versus 27), higher number of screen-detected cases (13 versus 7), and lower number of combined low-dose CTs and diagnostic follow-ups per death avoided (8 versus 5), per one million general population. Sensitivity analysis of nodule progression threshold verifies higher mortality reduction with 1-month earlier follow-up for Lung-RADS 3.

CONCLUSIONS: One month earlier diagnostic follow-ups for individuals with Lung-RADS category 3 nodules may result in higher mortality reduction and warrants further investigation.