Up to 40% of cancer patients use cannabis to help with treatment side effects like nausea, loss of appetite or pain.
But in a new paper published in JNCI Monographs, MUSC Hollings Cancer Center researchers show that patients who smoke cigarettes are also more likely to use cannabis, which may make cancer treatments less effective.
Most cancer centers, including Hollings, have active tobacco smoking cessation programs. But those programs don't necessarily collect data or incorporate information about cannabis, said senior author Erin McClure, Ph.D., a behavioral psychologist. For those who smoke both tobacco and cannabis, the two activities can at first seem inextricably intertwined, which can make quitting smoking more difficult.
The Hollings researchers teamed up with colleagues at Roswell Park Comprehensive Cancer Center in New York to survey cancer survivors at their two centers. One of the most significant differences between the two centers, for the purposes of this survey, was that New York has had a legal medical cannabis program since 2016.
The research team found that most of those who said they smoked cigarettes also preferred to smoke cannabis compared with other methods of cannabis use, such as edibles. In contrast, those who had never smoked cigarettes were more likely to prefer to use cannabis through prepared foods or taking pills or tinctures.
"If people are using inhaled methods of both, then one could serve as a trigger for the other, and one could lead to craving of the other, which then would make it far more difficult for somebody to quit smoking," McClure said.
"If people are using inhaled methods of both, then one could serve as a trigger for the other, and one could lead to craving of the other, which then would make it far more difficult for somebody to quit smoking."Erin McClure, Ph.D.
Cancer care providers definitely want patients to stop smoking cigarettes. Tobacco use among cancer patients can worsen treatment side effects, reduce the effectiveness of treatments, increase complications after surgery and increase death rates.
Cannabis use is more complicated. The researchers point out that although cannabis may help with cancer pain and other symptoms, some early studies have shown that cannabis may reduce the effectiveness of some types of treatments.
"Cannabis just isn't as well-assessed. And to be fair, I think a lot of providers just don't know what to do when people say that they're using it or they're interested in it and want to try it," McClure said. "Especially our providers here in South Carolina; you can't say, 'Well, go down the street to this dispensary and try this product and see what you think.'"
Aimee McRae-Clark, Pharm.D., who focuses her research on addiction as a disease state, including cannabis use disorder, noted that one predictable difference between cancer survivors at the two sites was that those in New York were more likely to know what was in the product they were using, in terms of percentages of THC or CBD.
"We are in a state that does not have any sort of legalized cannabis market, and so it stands to reason that folks are less certain about what they're using here because there's no packaging for the majority of what they're using," she said.
McClure said tobacco cessation programs may also need to begin to address cannabis use.
"I really think that there's a need in oncology settings to include cannabis screening and recommendations for providers and patients as well as harm reduction strategies for people who are using cannabis and find benefit and don't want to quit," she said.
Her research will contribute to the knowledge base that tobacco cessation programs draw from. This summer, McClure was awarded a grant from the National Cancer Institute to develop a clinical trial testing the use of varenicline - better known by its former brand name Chantix - to help co-users of tobacco and cannabis to quit smoking and either quit or reduce the use of cannabis.
The trial will be open to adult co-users throughout South Carolina, not just those with cancer, but the results will help to inform treatment options for counselors working with people being treated for cancer.
