Increased head and neck cancer linked to cannabis use

People who use cannabis, particularly those with a cannabis use disorder, are significantly more likely to develop head and neck cancers than nonusers, according to a recent study published in JAMA Otolaryngology–Head and Neck Surgery.¹

Adults with a cannabis use disorder, which was defined as excessive use of cannabis with associated psychosocial symptoms and impairment in functioning, were found to be 3.5–5 times more likely to develop head and neck cancer than nonusers of cannabis. The increased risk was seen for all site-specific head and neck cancers, including oral, oropharyngeal, and laryngeal cancers, and was consistent after stratification for older and younger age.

The finding adds to the list of modifiable risk factors associated with head and neck cancers, which include tobacco use, excessive alcohol consumption, and human papillomavirus exposure.

Niels C. Kokot, MD, a head and neck surgeon at the University of Southern California Keck Medicine and senior author of the study, says that the finding highlights cannabis use as a significant risk factor for head and neck cancer that warrants further investigation into causation.

“The next steps involve designing studies to determine the amount and type of cannabis use and how these factors impact the risk of head and neck cancer,” he says. “This will help us better understand the specifics of this association.”

In the study, Dr Kokot and his colleagues retrospectively reviewed 20 years of data from 64 health care organizations for US adults with (more than 116,000) or without (nearly 4 million) a cannabis use disorder recorded at an outpatient hospital clinic (patients with no prior history of head and neck cancer were chosen so that the relative risk of developing a new head and neck cancer could be compared between the two groups). The two groups were matched by demographic characteristics, alcohol-related disorders, and tobacco use, creating two cohorts of 115,865 each. In the cannabis use disorder group, cancer cases were tracked after 1 year of cannabis use for up to 5 years.

The relative risk of developing a new head and neck cancer was 3.49 for adults with a cannabis-related disorder compared to nonusers. A higher risk of developing a head and neck cancer in those with a cannabis-related disorder was seen across the different types of head and neck cancer, with a relative risk of 2.51 for oral cancer, 4.90 for oropharyngeal cancer, and 8.39 for laryngeal cancer (vs. nonusers).

Wojciech (Wojtek) Mydlarz, MD, director of Johns Hopkins Head and Neck Surgery for the National Capitol Region, says that the study is likely the “first large study to look at these numbers of patients and look at associations across a large population. Most providers do feel there is a real risk to develop head and neck cancer with most inhaled substances and exposures, whether they are tobacco or cannabis and others,” he says.

He says that all these inhaled substances are likely to have some systemic effects on the mucosal surfaces of the upper aerodigestive tract in the head and neck through exposure to chemicals and vapors in psychoactive compounds found in these substances. Moreover, he notes that cannabis use also may signal engagement in other high-risk behaviors, including sexual practices, that increase the risk of head and neck cancer.

Dr Mydlarz encourages physicians “not to shy away from” talking to patients about the risk of cannabis and other high-risk behaviors associated with head and neck cancer. “Make this part of routine conversation and screening,” he says, citing this as a key message by the American Head & Neck Society.²