SUMMARY: The American Cancer Society estimates that about 58,450 new cases of oral cavity and pharynx cancer will be diagnosed in the US in 2024 and about 12,230 patients will die of the disease. The head and neck region includes the oral cavity, oropharynx, hypopharynx and larynx. Squamous Cell Carcinoma of the Head and Neck accounts for about 3-5% of all cancers in the United States. Common risk factors include tobacco and alcohol use and Human PapillomaVirus (HPV) infection. Even though tobacco has long been associated with head and neck cancer development, cannabis has similar carcinogens.
Cannabis refers to all products derived from the plant Cannabis sativa, and is the most commonly used illicit substance worldwide. The cannabis plant contains about 540 chemical substances and has similar carcinogens as tobacco. Marijuana refers to the dried leaves, flowers, stems, and seeds from the plant Cannabis sativa that contain substantial amounts of TetraHydroCannabinol (THC), which is primarily responsible for the effects of marijuana on a persons mental state. Individuals with head and neck cancer have used cannabis to help alleviate pain and improve well-being. In 2022, 30.7% of 12th graders reported using marijuana in the previous year and 6.3% reported using marijuana daily. In addition, many young people also use vaping devices to consume cannabis products.
As cannabis use grows, understanding its carcinogenic potential becomes increasingly important, particularly given its rising popularity and industry expansion. Cannabis smoke may be more proinflammatory than tobacco smoke due to its unfiltered nature and higher combustion temperature. This increased inflammation could lead to cancer development. Cannabis smoke also enhances the expression of Epidermal Growth Factor Receptor (EGFR), which is associated with many head and neck squamous cell carcinomas, including Laryngeal cancer. It remained unclear if cannabis use is associated with increased risk of head and neck cancer.
The researchers conducted a large-scale, retrospective cohort study over a 20 year period from April 19, 2004, to April 19, 2024, to investigate whether there is an association between cannabis use and an increased risk of head and neck cancers. Given the growing prevalence of cannabis use and its potential health effects, understanding this relationship is crucial for public health. In this study, clinical records of 116,076 U.S. adults with and without cannabis-related disorders who had outpatient hospital clinic visits and no prior history of head and neck cancers were extracted from a database covering 64 healthcare organizations across the United States. The mean age of 46.4 years, 44.5% were women and 60% white. Cannabis-related disorder was defined as excessive cannabis use leading to psychosocial symptoms, including impaired occupational or social functioning. The control cohort consisted of 3,985,286 individuals with a mean age of 60.8 years (54.5% women, 74.6% white), with no cannabis-related disorder. Participants were matched for age, race, tobacco use, and alcohol-related disorders. Relative risks (RRs) for head and neck cancers and subtypes were calculated, with stratified analysis for those younger and older than 60 years.
It was noted that Individuals with cannabis-related disorder had a significantly higher risk of developing any type of head and neck cancer, compared to those without such disorders. Specifically, the risk for any head and neck cancer was 3.49 times greater in the cannabis-related disorder group. A site-specific analysis yielded that among those with cannabis-related disorder, Laryngeal cancer risk was 8.39 times higher, Oropharyngeal cancer risk was 4.9 times higher, Salivary gland cancer risk was 2.7 times higher, Nasopharyngeal cancer risk was 2.6 times higher and Oral cancer risk was 2.51 times higher. Risks were consistent across different age groups. Elevated risks persisted when cancer diagnoses were considered at least one year or five years after the initial cannabis use, indicating a sustained risk over time.
One of the study limitations was that the study did not capture information on the frequency, quantity, or type of cannabis use, which are crucial for understanding the dose-response relationship.
In conclusion, this study confirms a significant association between cannabis-related disorder and an increased risk of head and neck cancers, particularly Laryngeal and Oropharyngeal cancers. Future studies should focus on understanding the mechanisms behind this association and investigate the impact of cannabis use dose and duration on cancer risk. More comprehensive data collection and analysis are necessary to solidify these findings and inform public health recommendations.
Cannabis Use and Head and Neck Cancer. Gallagher TJ, Chung RS, Lin ME, et al. JAMA Otolaryngol Head Neck Surg. Published online August 8, 2024. doi:10.1001/jamaoto.2024.2419.
