Cannabis and cancer

Marijuana leaf in a petri dish in a lab, representing medical cannabis

Dried buds and leaves of cannabis sativa plant ease therapy symptoms for some people

Until recently, the use of marijuana, preferably called cannabis, was only considered legal in 36 U.S. states for the treatment of certain medical conditions. Yet with origins tracing back more than 5,000 years into the ancient world, the cannabis sativa plant — also known as cannabis — was first used medicinally around 400 A.D. In the U.S., it was used as a patent medicine in the 19th and early 20th centuries.

Today, contemporary research shows that the dried buds and leaves of the cannabis sativa plant can ease symptoms of cancer therapy for some people. So far, however, there is no concrete clinical evidence that cannabis can help to either control or cure any cancer.

“Cannabis has moderate evidence that it may help reduce chemotherapy-induced nausea and vomiting, and less robust evidence that it may reduce pain due to chemotherapy-induced peripheral neuropathy,” says Amy Case MD, FAAHPM, the Lee Foundation Endowed Chair of the Department of Palliative and Supportive Care at Roswell Park Comprehensive Cancer Center.

“But there are no large or high-level evidence trials that show that cannabis improves survival or reduces cancer,” she advises.

Botanical science of medical cannabis

Cannabis has more than 100 biologically active components called cannabinoids, also known as phytocannibinoids. The best studied compounds are delta-9-tetrahydrocannibinol (THC) and cannabidiol (CBD). Each of these has different effects on the body: THC, the main psychoactive cannabinoid, can help with pain and nausea, reduce inflammation and act as an antioxidant. CBD helps treat seizures, reduce anxiety and can stimulate appetite. The effects of cannabis depend on how these compounds enter the body. The most common ways are in food (edible cannabis) or by smoking or vaping it.

Edible cannabis: When taken by mouth, such as in drinks, baked goods or candy — or topically — the THC can take hours to be absorbed and processed by your liver. It’s important to know that the amount of THC in foods that have had cannabis added to them is often unknown, and getting too much THC might result in psychoactive adverse symptoms.

Inhaled cannabis: The THC in inhaled cannabis enters the bloodstream and goes quickly to brain, but the effects fade faster than with edible cannabis.

“Whole flower or balanced products that have both THC and CBD, ideally in a 1:1 or 2:1 ratio, are both effective and the best tolerated, whereas high-dose THC products can cause confusion, altered perception, or paranoia and should be used with caution in older or frail patients” Dr. Case says.

Patients with low blood counts, compromised immune systems and lung cancer or disease should not inhale cannabis because of the risk of possible fungal pneumonia from the whole flower product, or bacterial pneumonia from a vaped product, she warns: “They should use oral products only.”

What you should know about cannabis

Based on your medical history, you may be certified for any product, or for oral nonsmoking products only.

Learn more

Pros and cons of cannabis for cancer patients

While cannabis may be helpful for some patients in treating chemotherapy side effects — nausea, vomiting, poor appetite, insomnia or neuropathic pain — cannabis is still fundamentally a drug with the potential for harmful side effects.

“Medical cannabis can raise your heart rate and put patients at higher risk for heart attacks or strokes, especially if it is being smoked or vaped. Pregnant patients should always avoid cannabis as it can lead to several issues with the baby, including birth defects and developmental delays,” Dr. Case advises.

“It can worsen anxiety and paranoia, so patients who are prone to mental health conditions should use caution with using cannabis. Older adults should always be cautious with new drugs, and the same is true with cannabis, which may cause confusion or delirium, especially products with higher THC.” 

Given the complex U.S. history of cannabis, understanding the legality of its medical uses for cancer can be daunting. It is still labeled as a Schedule I Drug by the Drug Enforcement Administration, which means it is illegal under federal law. But the use of medical cannabis in some form — including as a pharmaceutical pill — is currently legal in 36 states, and recreational use of cannabis continues to be legalized in states across the country, including New York.

“Some medical providers may not be knowledgeable about the literature on cannabis and have a bias against its use due to the years of it being illegal and used recreationally,” says Dr. Case. “We do not judge people for using cannabis to control their medical symptoms in our clinic. However we do provide education for safe use and potential drug interactions.

“At Roswell Park, if a patient wishes to know details about the benefits and risks of cannabis, they can request to see us in the Supportive and Palliative Care clinic or any cannabis clinic in the community.”

Cannabis medications for therapy side effects

Providers sometimes prescribe medications based on cannabis compounds to help cancer patients manage the side effects of cancer therapy when other drugs don’t work. These include:

  • Dronabinol (Marinol / Syndros) contains THC and is approved by U.S. Food and Drug Administration (FDA) to treat nausea and vomiting caused by cancer therapy. It’s also used to help AIDS patients with weight loss and poor appetite.
  • Nabilone (Cesamet), a synthetic cannabinoid, works similar to THC, and can be taken as a pill to treat nausea and vomiting caused by chemotherapy.

“These drugs should be used with caution as they can cause confusion or paranoia, but they are FDA approved for poor appetite in the setting of AIDS and chemotherapy-induced nausea and vomiting,” Dr. Case says. “Some patients taking nabilone in studies reported hallucinations. The drugs may increase some effects of sedatives, sleeping pills, or alcohol, such as sleepiness and poor coordination. Patients have also reported problems with dry mouth and trouble with recent memory.”

Nabiximols, a cannabinoid drug made up of a whole plant extract using both THC and CBD and administered as a mouth spray, is still under study in the U.S. Available in Canada and parts of Europe to treat pain linked to cancer, it is being tested in clinical trials here.

“Many times, patients may not report the same beneficial effects from just a synthetic THC product alone when compared to the combined effect from the whole plant, which includes flavonoids, terpenes and other cannabinoids which may have unproven beneficial effects.”

Supportive Care at Roswell Park

Our Supportive and Palliative Care program provides essential support and symptom management to our patients, at any point in their cancer journey.

Learn how we can help

The future of cannabis and cancer research

Because cannabis is still classified as a Schedule I controlled substance, scientific research on the potential of cannabinoids to translate into effective therapies that can improve the often-debilitating side effects of cancer and its treatment are hampered by FDA and DEA regulations.

“Some of the scientific research to back up the benefits of cannabis is lower quality and the few higher quality studies show mixed results, with some trials showing benefit and some not.

"Larger, blinded, randomized and placebo-controlled, higher-quality studies are needed,” Dr. Case says.

The Roswell Park Center for Translational Research on Cannabis in Cancer is leading several studies on cannabis in cancer patients that are funded by the National Institutes of Health. Says Dr. Case: "Our studies are looking at patterns of use, labeling, pharmacokinetics, safety, benefits for symptoms and interactions with immunotherapy, among others.”