Objective. Process evaluation of the Yorkshire Enhanced Stop Smoking (YESS) study intervention, to provide evidence regarding optimal integration of smoking cessation support within lung cancer screening (LCS). Design. Mixed-methods process evaluation. Setting. YESS was a Randomised Controlled Trial testing the effect of personalised smoking cessation support, integrated within LCS. YESS study participants were recruited from the Yorkshire Lung Screening Trial. Participants/data collection. Semi-structured interviews with 45 trial participants and eight SCPs 4, 12 and 52-weeks after screening (participants) or training (SCPs). Thematic analysis to assess intervention exposure, context, contamination and theory. Observations of SCP consultations on the screening unit (n=84; 4%) and 4-weeks after screening (n=132; 13%) tested intervention fidelity. Intervention. The YESS study tested opt-out, co-located standard best practice (SBP) smoking cessation support (control) versus a theory-informed personalised risk information booklet designed to increase efficacy beliefs in addition to SBP (booklet intervention), delivered by trained smoking cessation practitioners (SCPs). Results. Intervention context was paramount: participants in both trial arms described benefits of co-located and ongoing high-intensity smoking cessation support, with immediate provision of pharmacotherapy. Tailored, non-judgemental care was considered key to initiating and sustaining quitting, particularly for participants at various points along their quit or those awaiting their scan result. Fidelity was high (98%) and moderate (75%) for SBP, moderate (77%) for the booklet intervention. Exposure varied by participants needs, including their screening results. Potential contamination was observed, with SCPs delivering elements of the booklet intervention training across both trial arms. Conclusions. A personalised approach is critical to supporting smoking cessation in LCS. Harnessing the benefits of LCS for supporting cessation at the time of screening requires investment in specialist practitioners to deliver person-centred smoking cessation support. Trial registration. www.clinicaltrials.gov/study/NCT03750110

RT, PC have received payment/honoraria for a webinar with Bayer. DRB has received lecture honoraria with Astra Zeneca, MSD and Roche. RM has received consulting fees from Action on Smoking and Health and Cancer Research UK. RM is a Trustee of Action on Smoking and Health and a member of the Royal College of Physicians Tobacco Advisory Group. All other authors declare no conflicts of interest

NCT03750110

https://doi.org/10.1136/bmjopen-2020-037086

This work was funded by Yorkshire Cancer Research (award references L403 and NOT414). From September 2021, P. Alexandris was supported by the Barts Charity (MRC&U0036). From January 2021, S.L. Quaife was supported by the Barts Charity (MRC&U0036). R.J. Beeken is supported by a Yorkshire Cancer Research Fellowship (L389RB). P.A.J. Crosbie is supported by the Manchester National Institute for Health Research Manchester Biomedical Research Centre (IS-BRC-1215-20007). H. D. Quinn-Scoggins is supported by Health and Care Research Wales as part of the Primary and Emergency Care Research Centre (PRIME) (517195). G. McCutchan is supported by Health and Care Research Wales as part of the Wales Cancer Research Centre (517190).

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