Introduction:
Mobile phone-based smoking cessation intervention has shown promise in helping people to quit. Many, however, continue to smoke after receipt of chat-based intervention. Adaptive trial design allows modifications of intervention contents based on smoker’s needs and preferences.

Objectives:
This study aimed to explore the experiences of continuing smokers on using the chat-based support through mobile phone instant messaging apps, to explore their perspectives on what optional supports could help in quitting, and to inform the development of future trials using an adaptive design to maximize practical applicability in the community.

Methods:
Purposive sampling was used to recruit community smokers who were unable to quit after participating in our previous chat-based smoking cessation trials. The semi-structured interview guide included: (1) experiences of using chat-based support (2) reasons for continuing smoking and (3) suggestions on the content of optional cessation supports to optimize the proposed adaptive trial. The interviews were transcribed and analyzed using thematic framework analysis.

Results:
Thirteen interviews were conducted (11 males and 2 females aged 25-67 years). Participants agreed regular instant messages from a counselor provided behavioral and psychosocial support for their quit attempts. Busy work and low interest were the main barriers for not engaging in chat-based intervention. Low motivation to quit, high addiction to nicotine and lack of social support were emerged as important factors contributing to continuous smoking. Participants felt their quit attempts would be aided by offering optional cessation supports such as nicotine replacement therapy, personalized referral assistance to smoking cessation service, individual phone counseling, visualized smoking cessation messages and support from family/peer group.

Conclusion(s):
Chat-based smoking cessation support was underused. Continuing smokers may benefit from flexible adaptive trials that providing optional cessation supports according to their preferences. The findings will inform the development of an adaptive chat-based smoking cessation trial in the community.