Outcomes of Long-term Interval Rescreening With Low-Dose Computed Tomography for Lung Cancer in Different Risk Cohorts

IntroductionWe hypothesize that the incidence of screen-detected lung cancer (LC), in participants with previously negative scans, will be highest in the cohort with the highest baseline risk score.MethodsIndividuals with negative baseline screening results from the Princess Margaret International Early Lung Cancer Action Program before 2009 underwent low-dose computed tomography rescreening from 2015 to 2018. Individuals were contacted in order of descending risk, as determined by the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial's PLCO_M2012 6-year LC risk-prediction model, and then categorized into three risk cohorts according to their baseline risks. The incidence of LC in each risk cohort was determined and compared. Chi-square testing was used for categorical variables and one-way analysis of variance on ranks was used for continuous variables.ResultsOf the 1261 participants we attempted to re-contact, 359 participants returned for a rescreening scan (mean of 7.6 years between scans). Participants were divided into low (<2%), moderate (≥2% to <3.5%), and high baseline risk (≥3.5%) cohorts. On average, those in the high-risk cohort compared to the moderate- and low-risk cohorts were older (66 years versus 62 and 59 years) and had a greater smoking history (54 pack-years versus 47 and 29 pack-years). The incidence of cancer in the high-risk cohort was significantly higher than in the moderate-risk cohort (11% versus 1.7%, p = 0.002).ConclusionsThere was a significantly higher incidence of LC in the high-risk cohort than in the moderate-risk cohort. The cut-point between the high- and moderate-risk was determined to be greater than or equal to 3.5% of the 6-year baseline risk.