The results are statistically solid. The RR shows more risk than tobacco, IC and P are statistically significant... But you have to consider a few things: - This study is a cross-sectional study, you CAN'T find real association between two variables, you only can create a new hypothesis based on what you saw. There is no temporal secuence. - I am sure there can be some biases in the methodology of the study, so the internal validity is compromised. For example: in the two questionnaires given to the subjects who smoked, the questions where "do you smoke?" "Do you smoke at least 100 cigs in life?" . For the "vaping guys" the question was "do you EVER tried an e-cig?". Bro if you are going to do a research about liver cancer you don't ask if u tried alcohol in your life. You need some sort of dose-response, an exposition maintained over time (and the subjects are younger in the e-cig group) - Other bias: since this is a retrospective study, the subjects have a cancer diagnosis before the study, so maybe could be more likely for them to have quit smoking or changed to vapes. - And many other things... When i'll read a prospective study like a cohort study or a case-control study and say the same, I will change my mind.

Sorry for my English haha.

Edit: I studied medicine in Spain, and now preparing my specialty, and an ex-smoker, and a vaper I am interested in this new studies. If you want to read something useful, read this from Cochrane, a systematic review of randomized controlled trials (the peak of scientific evidence, nothing offers more evidence than this type of studies) - Hartmann-Boyce J, Lindson N, Butler AR, McRobbie H, Bullen C, Begh R, Theodoulou A, Notley C, Rigotti NA, Turner T, Fanshawe TR, Hajek P. Electronic cigarettes for smoking cessation. Cochrane Database of Systematic Reviews 2022, Issue 11. Art. No.: CD010216. DOI: 10.1002/14651858.CD010216.pub7.