Importance of Long-term Low-Dose CT Follow-up after Negative Findings at Previous Lung Cancer Screening.

Purpose To assess the incidence of lung cancer in a cohort of patients with negative findings at previous lung cancer screening. Materials and Methods In this prospective cohort study, the authors first identified 4782 individuals who had negative screening results as part of the International Early Lung Cancer Action Program (1993-2005). Subjects were assigned a lung cancer risk score by using a validated risk model. Starting with those at highest risk, subjects were interviewed by phone and invited to undergo low-dose CT between March 2013 and October 2016. Subjects with a diagnosis of lung cancer and those who had died of lung cancer were determined. Descriptive statistics were used to summarize data. The independent samples t test and Fisher exact test were used to compare age, sex, and risk scores. Results A total of 327 study participants were contacted, and 200 subjects participated in this study. The average age was 74 years (range, 57-88 years), and the median time since previous CT was 7 years. The incidence rate of developing lung cancer during the next 6 years was estimated at 5.6%. The period prevalence of lung cancer was 20.8% (new and preexisting lung cancer, 68 of total cohort of 327). The detection rate of low-dose CT was 7% (14 of 200 subjects). Of the 14 screening-detected cancers, 12 were stage I or II. Conclusion High-risk individuals have a high incidence of lung cancer after previous negative lung cancer screening. Early-stage lung cancer can be successfully detected in older high-risk individuals. © RSNA, 2018 Online supplemental material is available for this article.