Marijuana and head and neck cancer: an epidemiological review

Abstract Background Marijuana is the most widely used illicit substance in Canada. To date, no conclusive study has looked at the epidemiologic basis of marijuana use and head and neck cancer (HNC). Due to the imminent recreational legalization of marijuana in Canada, the epidemiologic relationship between marijuana use and HNC is becoming increasingly important. Objective To examine the epidemiologic characteristics of HNC patients who are recreational marijuana users. Methods This study was conducted at a single tertiary care centre from 2011 to 2014. Patients were enrolled consecutively at time of diagnosis of malignancy. Data was prospectively collected and included socioeconomic factors, alcohol/tobacco history, tumor characteristics, and treatment modality. Marijuana use was defined as current usage on an at least weekly basis. Results Eight hundred seventy-nine patients met inclusion and exclusion criteria. Seventy-four (8.4%) patients were classified as marijuana users. Compared to non-users, marijuana users were less likely to be married (p = 0.048) and had less significant tobacco smoking history (p = 0.004). There were no significant differences between other socioeconomic factors or local and regional disease (p > 0.05). Marijuana users differed in the proportion of cancers stratified by primary site (p < 0.0001), with higher rates of p16+ oropharyngeal cancers, and treatment modality (p < 0.0001), with more use of chemoradiation. Conclusions HNC patients who were marijuana users were less likely to be married and smoke tobacco. They have a distinct cancer site prevalence and are more likely to be treated by chemoradiation. Understanding the epidemiological breakdown of marijuana users amongst HNC patients will be a useful adjunct for future studies