Borderud 2014

Methods	Design: Prospective observational cohort study Recruitment: Patients presenting with cancer at large US cancer centre; smokers referred to tobacco cessation programme (TCP). This study included all patients who completed TCP intake assessment, 2012 ‐ 2013 Setting: Cancer centre, USA Inclusion criteria: Smokers (smoked cigarettes or used other tobacco products within past 30 days) accepting cessation programme Exclusion criteria: none stated
Participants	Total N: 1074. 781 eligible for 6 ‐ 12m follow‐up 56.5% women, mean age 56, mean cpd 13, mean FTND 3.7. At baseline, 26.5% (285/1074) had used EC within last 30 days, 92% dual users
Interventions	All participants offered "multicomponent, evidence‐based behavioral and pharmacologic treatment for tobacco dependence”; plans differed by individual but offered up to 5 sessions of phone or in‐person counselling
Outcomes	Follow‐up ranged from 6 to 12m after enrolling in TCP (mean 10m). Collected: Self‐reported 7‐day PP abstinence Gone at least 1 day without smoking CPD
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Observational
Allocation concealment (selection bias)	High risk	Observational
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Although there is no blinding, the study design means that there is unlikely to be significantly impact on performance
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Self‐report only but differential misreport across EC conditions judged to be unlikely
Incomplete outcome data (attrition bias) All outcomes	High risk	Large number of participants (285) lost to follow‐up (of eligible, 59.5% followed up). A further 82 deceased “significantly higher percentage of E‐cigarette users dropped out of tobacco treatment and were lost to follow‐up than non–E‐cigarette users”. Complete‐case analysis not significant, ITT analysis significant.
Selective reporting (reporting bias)	Unclear risk	Unable to determine prespecified outcomes