E-cigarettes and head and neck cancers: A systematic review of the current literature

Background: Cigarette smoking is a well-established risk factor for head and neck (HN) cancers. Use of electronic cigarettes (e-cigarettes) is gaining popularity, being advertised as benign alternatives to tobacco. A wide variety of potentially harmful chemical components with variable quantity have been identified in e-liquids and aerosols of e-cigarettes. However, use of e-cigarettes remains controversial due to conflicting evidence.

Objectives: We aimed to assess the association between e-cigarettes and HN cancers. We conducted a systematic review to evaluate the literature for evidence on carcinogenic effects of e-cigarettes in the pathogenesis of HN cancers.

Type of review: Qualitative systematic review.

Search strategy: A PubMed/MEDLINE, Cochrane, CINAHL Plus, Trip Medical Database and Web of Science search was done for studies on e-cigarettes and HN cancer.

Evaluation method: Abstract review of all articles, full article revision of included studies, data extraction and quality assessment were performed by two independent assessors.

Results: The literature search resulted in the identification of 359 articles. Eighteen articles were selected for inclusion into the systematic review. The majority were laboratory-based studies, followed by several cohort and case studies, representing low-level evidence. A few reports suggested DNA damage following exposure to e-cigarettes potentially due to increased oxidative stress. Flavoured e-liquids appear to be more harmful. There is variable evidence from clinical studies.

Conclusions: Our review outlines potential dangers associated with the use of e-cigarettes and their role in HN cancers. More longitudinal and controlled studies are needed to assess the possible link between e-cigarettes and HN cancers.