Association between cigarette smoking and nasopharyngeal cancer risk: a meta-analysis

Introduction: Nasopharyngeal cancer (NPC) is a relatively rare yet aggressive malignancy, primarily affecting regions of East and Southeast Asia. This study aims at providing an up-to-date quantification of the association between cigarette smoking and NPC risk, overall and by histological subsites. Methods: We conducted a systematic review and meta-analysis of case-control and cohort studies on the association between cigarette smoking and NPC risk published up to May 2023. The methodology used is original and efficient and includes both a comprehensive umbrella review and a traditional review. We estimated pooled relative risks (RR) of NPC according to smoking status, intensity, duration, and time since quitting. Results: Among 46 eligible articles, 40 original studies were included in this meta-analysis. Compared with never smokers, the pooled RR of NPC was 1.61 for current, 1.28 for former, and 1.62 for ever smokers. The RR for ever compared with never smokers was 2.37 for squamous cell NPC and 1.06 for undifferentiated NPC. NPC risk significantly increased linearly with smoking intensity and duration, and decreased linearly with increasing time since quitting. Conclusion: This meta-analysis confirms the link between tobacco smoking and NPC, highlighting the significant risk posed even by moderate cigarette consumption. Additionally, our findings underscore the differential risk between squamous cell and undifferentiated subtypes of NPC, shedding light on the distinct implications for NPC prevention strategies.