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 aimsDespite 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.DesignThis will be a multi-centre, two-arm (1:1), single-blind, pragmatic, individually randomized controlled trial.SettingTaking part will be specialist outpatient clinics in five major hospitals in different location-based clusters in Hong Kong.ParticipantsThe sample will include 1448 Chinese smokers living with cancer attending medical follow-ups at outpatient clinics.InterventionsThe 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.MeasurementsThe 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.CommentsThe 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.