CBD is everywhere, but is it safe for cancer patients?

While some anecdotal evidence has been publicly shared about CBD’s benefits for cancer patients, the scientific research is lacking.

It seems nearly everywhere you look these days someone is selling, pitching or endorsing CBD, the acronym for cannabidiol, one of the key ingredients in cannabis. Whoopi Goldberg, Tom Hanks and Olivia Wilde are just a few celebrities to tout CBD as an elixir for conditions such as endometriosis, fibromyalgia, PTSD, anxiety, muscle tension and insomnia.

Grammy Award-winning singer Melissa Etheridge says CBD helped her combat the “collateral damage” of chemotherapy during her treatment for breast cancer. Other segments of the cancer community maintain that CBD is an antidote to chronic pain, chemotherapy-induced nausea, vomiting, neuropathy and appetite loss.

Forbes reported in 2019 that CBD sales in the United States will top more than $20 billion by 2024. Still, many consumers may not be aware that the U.S. Food and Drug Administration (FDA) has not approved the use of CBD in any over-the-counter products. And, with one exception, the FDA has not approved CBD to treat any condition or disease, including cancer. The FDA, so far,  has approved just one cannabidiol drug—Epidiolex®—for the treatment of seizures associated with two forms of epilepsy, Lennox-Gastaut syndrome and Dravet syndrome, and for tuberous sclerosis complex, a condition that causes benign tumors to grow throughout the body.

Available only by prescription, Epidiolex contains a highly purified form of CBD, the FDA says. Safety risks include possible liver damage and the potential for adverse reactions when the drug is taken with other medications—potential hazards that the FDA requires be disclosed on its label.

Cancer and CBD

While some anecdotal evidence has been publicly shared about CBD’s benefits for cancer patients, the scientific research is lacking. The situation causes a conundrum for doctors who treat cancer patients, says Maurie Markman, MD, President of Medicine & Science at Cancer Treatment Centers of America® (CTCA).

“There are individuals who clearly say it works, groups and medical societies, such as ASCO (American Society of Clinical Oncology), that say it may be of value,” Dr. Markman says. “States say it’s legal, and the FDA says it’s looking at it. But the problem is we do not have clinical trials conducted by the FDA to show its safety and efficacy relative to drugs that are already out there. At a patient and doctor level, it’s a very difficult situation. Doctors need scientific evidence, not anecdotal evidence, that something is safe and effective.”

CBD is thought to work by targeting cannabinoid receptors (CB1 and CB2) found mainly in the brain and other areas of the body. These receptors are part of the endocannabinoid signaling system, which—while its role is not completely understood— is believed to help regulate various mental functions, including cognition, sleep, pain and mood. CBD may also help regulate the production of cortisol, a hormone that helps the body deal with stress.

CBD comes in many forms—creams, capsules, edibles, tinctures and oils, including a vaping oil. Unlike another key ingredient in the cannabis plant, tetrahydrocannabinol, or THC, CBD does not cause users to feel high. CBD may be found in grocery stores, marijuana dispensaries, gas stations, pharmacies and health food stores. It can be smoked, vaped, drunk or eaten.

The FDA acknowledges the “significant public interest in cannabis and cannabis-derived compounds,” but maintains there are “many unanswered questions about the science, safety, and quality” of CBD products. The agency is engaged in “ongoing efforts” to answer these questions, according to its website.

Danish researchers conducted a review of 22 clinical trials conducted over a 19-year span on the use of cannabis and CBD in adults. They concluded that, while CBD may have “therapeutic effects” on some social and psychiatric disorders, the studies showed “substantial risks of bias” and had varying “methodological weaknesses.”

CBD, as well as medical marijuana, must be studied in the same way all other FDA-approved drugs are, by conducting randomized trials, its effects on various age groups and populations, and comparisons to already approved drugs, Dr. Markman says. To date, he says, no studies have met the agency’s criteria or standards to win FDA approval, which Dr. Markman calls “the gold standard.” In order to do so, experts must determine that a drug’s benefits “outweigh the known risks for the intended use,” he says.

“In its absence, it doesn’t mean something isn’t of value, but it’s much harder to advise its use in patients,” Dr. Markman says. "There’s no regulation. The research just isn’t there yet. The fundamental problem has been, and remains, that you’re talking about a class of drugs that’s been woefully under-researched, and the reason is because it’s illegal under federal law. It’s an incredible situation where you have proclamations by people about how great it is, but we also know about the placebo effect, which is a very important consideration. There have also been multiple studies that have shown potential for harm to the central nervous system and cognition. And there’s an incredible economic incentive to consider.”

Dr. Markman says he doesn’t discount the many doctors and patients who swear by the plant’s medicinal benefits, but he strongly recommends that any cancer patient contemplating using a CBD product, or medical marijuana, have a conversation with his or her oncologist before doing so.

“It’s very important that patients and their doctors discuss their very specific situation regarding what they’d like to take it for, what the alternatives are, the potential side effects of alternatives, and the potential benefits they’re looking for,” he says. “Hopefully, the information the doctor is relying on to help that patient make a decision is valid, useful, helpful, unbiased and scientifically rigorous. Ultimately, it’s each individual patient’s decision.”

Learn more about medical marijuana and cancer.