Background: Few epidemiological data exist on the lung cancer (LC) risk of E-cigarettes (ECIGs) and heated tobacco products (HTPs).
Aim: To estimate the LC risk of these new tobacco products (NTPs) from their levels of biomarkers of exposure (BOEs) and potential harm (BOPHs).
Methods: For 28 BOE and 82 BOPH groups we sought North American and European biomarker data for cigarette smokers and users of other established tobacco products (ETPs; cigars, pipes, smokeless tobacco (ST) and/or snuff/snus). Using also ETP-specific LC relative risk (RR) estimates vs. non-users from recent meta-analyses of epidemiological studies in these regions we derived a regression model predicting the LC RR by level of each biomarker. For each NTP with relevant biomarker data, its LC risk was then estimated by combining RR estimates for selected biomarkers. Our main estimates considered only biomarkers significantly (p<0.01) fitting the model, and showing no significant (p<0.01) misfit to the RR of 1.0 for non-users.
Results: From 38 publications, biomarker data for ETPs were available for 56 BOEs in 21 of the 28 groups and for 54 BOPHs in 29 of the 82. The regression slope fitted to the LC risk was significant (p<0.01) for 22 BOEs and six BOPHs, though the predicted RR for non-users significantly (p<0.01) differed from 1.0 for 16 of these biomarkers.
The estimated LC RR for ECIGs, derived from 30 estimates for 10 biomarkers, was 1.88 (95% confidence interval (CI) 1.60-2.22), an excess risk (ER = RR−1) 6.8% of that for cigarette smokers. The RR generally varied little in sensitivity analyses, but increased markedly where the restriction to significant model fit was removed, the results then including some huge implausible RRs.
The estimated LC RR for HTPs, combining individual estimates for four BOEs was 1.44 (0.41-5.08), the ER being 3.4% of that for cigarette smokers.
Conclusions: Our methodology has limitations, but seems useful for estimating risk given no epidemiological data. Using biomarkers satisfactorily fitting the model suggests the LC risk from ECIGs is much lower than from cigarettes. Limited data indicate that risk from HTPs is also low. Future research using additional data could extend these findings.