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

INTRODUCTION:We 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. METHODS:Individuals 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 PLCOM2012 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. RESULTS:Of 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). CONCLUSIONS:There 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.