Cannabis and Cancer Part 2: Scientists Look for Ways to Increase Knowledge About Cannabis with Help from People with Cancer


Date Posted, by NCI Staff

After decades of opposition to decriminalizing cannabis products (especially marijuana), a more permissive attitude toward cannabis and its derivative products has taken hold today at the state level. At the same time, inconsistencies in state policies conflict with federal law, which itself, scientists said at a recent NCI-sponsored Cannabis, Cannabinoids, and Cancer Research Symposium, is hampering clinical research.

Federal law still defines cannabis products as illegal, even though a majority of states allow medicinal use of them for symptom relief in cancer and other diseases. In addition, 15 states and the District of Columbia have approved legalized use of cannabis products for both medicine and recreation. There are stringent federal licensing requirements that restrict access to a limited spectrum of cannabis products for research.” This comes at a time when cannabinoid products are flooding the marketplace including everything from cannabis-laced teas and cakes to cannabis-infused socks.

“We need national guidance,” Norman Sharpless, M.D., director of the National Cancer Institute, told participants at the virtual, four-day symposium to assess the science and help guide NCI’s research going forward. “Cancer patients are very interested in these products,” even though there is limited and conflicting data on their effectiveness and safety.

Some scientists at the meeting suggested that the strongest research supports the use of cannabis to ease chemotherapy’s side effects (discussed in part 1 of this two-part blog), such as nausea and vomiting, while other claims, such as whether cannabis “cures” cancer, lack scientific evidence and require further study. To begin addressing the research gaps, Dr. Sharpless said NCI has launched a nationwide survey of 12,000 people with cancer to assess their use of cannabis and related products. “Understanding how cancer patients use cannabis is important, along with understanding both potential benefits and risks. The survey results will help guide future research.”

The symposium participants also pointed out the need to evaluate the possible risks of cannabis use in both cancer patients and those without cancer. Long-term use in otherwise healthy people has been associated with health issues including cognitive delays and impaired motor coordination; acute psychosis and worsening mental health; and cannabis hyperemesis syndrome, a severe vomiting and nausea condition, increasingly seen in emergency rooms.

In 2019, a national outbreak in lung injuries occurred among individuals vaping e-cigarettes containing a mixture of a vitamin E additive and the two most common compounds in the cannabis plant, THC (tetrahydrocannabinol) and CBD (cannabidiol). Benjamin Blount, Ph.D., of the US Centers for Disease Control and Prevention spoke about these potentially harmful exposures. Some 2,800 individuals required hospitalization at the time and the CDC confirmed 68 deaths as of 2020 in 29 states and the District of Columbia.

A “Deep Dive” Is Needed Into the Products People Are Using

As these developments play out, scientists at the NCI-sponsored meeting described ways to improve research, despite continuing legal restrictions at the federal level. Detailed epidemiological information on cancer patients’ use of cannabis remains vital as a starting point, they said, especially which cannabis products are being used and exactly how they are used.

llana Braun, M.D., chief of the division of adult psychosocial oncology at Dana-Farber Cancer Institute, also argued for more research—a “deep dive”—into how people with cancer are using cannabis products. Areas of inquiry could include: Do they use cannabis only occasionally or regularly? Is their use primarily while receiving treatment, or does it continue after treatment, and for how long? Do they use these products in consultation with their healthcare providers, or independent of medical advice?

Dr. Braun also said medical schools should be required to convey the risks and benefits of cannabis to medical students. A 2018 study found that over half of doctors surveyed felt they did not understand cannabis well enough to recommend it, a finding underscored by 22-year-old Stacey Blansky, who provided a cancer patient’s perspective at the symposium. “My doctor had no evidence for me, so I had to read a lot of studies on my own,” she said. “It would just be nice if providers could provide that information.”

Symposium attendees also discussed ways to do clinical trials to get the best quality data while working around regulatory and product availability issues. Investigators have difficulty enrolling patients who now have easy access to cannabis products in the marketplace, and the trials are difficult to fund, said Mark Wallace, M.D., chairman of the division of pain medicine at the University of California San Diego School of Medicine. Once studies are funded, regulatory issues have delayed the start of some studies for as long as 3 years.

Finally, as basic scientists work to unravel the biology of the endocannabinoid system at the molecular level, there is a need to collaborate better with clinicians to move preclinical findings from the bench to the bedside. One preliminary finding showed that cannabis may interact with some cancer agents (such as immunotherapy) and reduce their efficacy. Another suggested cannabis may enhance the anti-tumor activity of the main treatment for glioblastoma, an aggressive brain cancer. “We tend to work in our own silos,” suggested Aron Lichtman, Ph.D., a professor of pharmacology and toxicology at Virginia Commonwealth University. “We’re good with mice and rats, but we need to work more closely with clinicians to develop the best targets and tools to move forward.”

An overview of the proceedings from the Cannabis, Cannabinoids, and Cancer Research Symposium is expected to be published later this year.

Part 1 of this blog addresses despite lack of evidence, cannabis products being widely used.

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