Effectiveness of a self‐determination theory‐based smoking cessation intervention plus instant messaging via mobile application for smokers with cancer: Protocol for a pragmatic randomized controlled trial

Background and aims Despite evidence that patients living with cancer who continue to smoke after diagnosis are at higher risk for all‐cause mortality and reduced treatment efficacy, many cancer patients continue to smoke. This protocol is for a study to test the effectiveness of a self‐determination theory‐based intervention (quit immediately or progressively) plus instant messaging (WhatsApp or WeChat) to help smokers with cancer to quit smoking. Design This will be a multi‐centre, two‐arm (1:1), single‐blind, pragmatic, individually randomized controlled trial. Setting Taking part will be specialist outpatient clinics in five major hospitals in different location‐based clusters in Hong Kong. Participants The sample will include 1448 Chinese smokers living with cancer attending medical follow‐ups at outpatient clinics. Interventions The intervention group will receive brief advice (approximately 5–8 minutes) from research nurses in the outpatient clinics and then be invited to choose their own quit schedules (immediate or progressive). During the first 6‐month follow‐up period they will receive instant messaging with smoking cessation advice once per week for the first 3 months, and thereafter approximately once per month. They will also receive four videos, and those opting to quit progressively will receive a smoking reduction leaflet. The control group will also receive brief advice but be advised to quit immediately, and instant messaging with general health advice during the first 6‐month follow‐up period using the same schedule as the intervention group. Participants in both groups will receive smoking cessation leaflets. Measurements The primary outcome is biochemically validated smoking abstinence at 6 months, as confirmed by saliva cotinine level and carbon monoxide level in expired air. Secondary outcomes include biochemically validated smoking abstinence at 12 months, self‐reported 7‐day point prevalence of smoking abstinence at 6 and 12 months, self‐reported ≥ 50% reduction of cigarette consumption at 6 and 12 months and quality of life at 6 and 12 months. All time‐points for outcomes measures are set after randomization. Comments The results could inform research, policymaking and health‐care professionals regarding smoking cessation for patients living with cancer, and therefore have important implications for clinical practice and health enhancement.