Analysis of lung cancer risk model (PLCO and LLP) performance in a community-based lung cancer screening programme.

Introduction: Low-dose CT (LDCT) screening of high-risk smokers reduces lung cancer (LC) specific mortality. Determining screening eligibility using individualised risk may improve screening effectiveness and reduce harm. Here, we compare the performance of two risk prediction models (PLCO and Liverpool Lung Project model (LLP)) and National Lung Screening Trial (NLST) eligibility criteria in a community-based screening programme.

Methods: Ever-smokers aged 55-74, from deprived areas of Manchester, were invited to a Lung Health Check (LHC). Individuals at higher risk (PLCO score ≥1.51%) were offered annual LDCT screening over two rounds. LLP score was calculated but not used for screening selection; ≥2.5% and ≥5% thresholds were used for analysis.

Results: PLCO ≥1.51% selected 56% (n=1429) of LHC attendees for screening. LLP ≥2.5% also selected 56% (n=1430) whereas NLST (47%, n=1188) and LLP ≥5% (33%, n=826) selected fewer. Over two screening rounds 62 individuals were diagnosed with LC; representing 87% (n=62/71) of 6-year incidence predicted by mean PLCO score (5.0%). 26% (n=16/62) of individuals with LC were not eligible for screening using LLP ≥5%, 18% (n=11/62) with NLST criteria and 7% (n=5/62) with LLP ≥2.5%. NLST eligible Manchester attendees had 2.5 times the LC detection rate than NLST participants after two annual screens (≈4.3% (n=51/1188) vs 1.7% (n=438/26 309); p<0.0001). Adverse measures of health, including airflow obstruction, respiratory symptoms and cardiovascular disease, were positively correlated with LC risk. Coronary artery calcification was predictive of LC (OR 2.50, 95% CI 1.11 to 5.64; p=0.028).

Conclusion: Prospective comparisons of risk prediction tools are required to optimise screening selection in different settings. The PLCO model may underestimate risk in deprived UK populations; further research focused on model calibration is required.