Sites of origin of oral cavity cancer in nonsmokers vs smokers: possible evidence of dental trauma carcinogenesis and its importance compared with human papillomavirus.

IMPORTANCE The relatively high and possibly rising incidence of mouth squamous cell carcinoma in nonsmokers, especially women, without obvious cause has been noted by previous authors. Is chronic dental trauma and irritation a carcinogen, and what is its importance compared with human papillomavirus (HPV) oropharyngeal cancer in nonsmokers? OBJECTIVE To determine whether oral cavity cancers occurred more commonly at sites of dental trauma and how the position of these cancers varied between nonsmokers lacking major identified carcinogens and smokers. If these cancers occurred more frequently at sites of chronic trauma, especially in nonsmokers, it would suggest chronic dental trauma as a possible carcinogen. DESIGN, SETTING, AND PARTICIPANTS A retrospective analysis of 881 patients with oral cavity or oropharyngeal cancers seen through a tertiary referral hospital between 2001 and 2011 was performed. MAIN OUTCOMES AND MEASURES Patient medical records were analyzed to determine the location of the tumor within the oral cavity and oropharynx and how it relates to patient demographics, smoking and alcohol histories, and comorbidities. Dental histories were also sought, including use of dentures. RESULTS Nonsmokers comprised 87 of 390 patients with mouth cancer (22%) and 48 of 334 patients with oropharyngeal cancer (14%). Female nonsmoking patients included 53 with oral cancer (61%) but only 12 with oropharyngeal squamous cell carcinoma (25%). Oral cancers occurred on the lateral tongue, a potential site of chronic dental trauma, in 57 nonsmokers (66%) compared with 107 smokers/ex-smokers (33%) (P < .001). Gingival and floor of mouth lesions occurred in older patients, possibly from chronic denture rubbing. Twenty-six patients had dental abnormalities recorded in close proximity to where their tumor developed. CONCLUSIONS AND RELEVANCE Oral cavity cancers occur predominantly at sites of potential dental and denture trauma, especially in nonsmokers without other risk factors. Recognizing teeth irritation as a potential carcinogen would have an impact on prevention and treatment strategies.