Cannabis in Cancer: What Oncologists, Patients Should Know

Many patients use cannabis to manage their cancer-related symptoms. However, research indicates that patients often do so without speaking to their oncologist first, and oncologists may be hesitant to broach the topic with their patients.

Updated guidelines from the American Society of Clinical Oncology (ASCO) on the use of cannabis and cannabinoids in adults with cancer stress that it’s an important conversation to have.

According to the ASCO expert panel, access to and use of cannabis alongside cancer care have outpaced the science on evidence-based indications, and overall high-quality data on the effects of cannabis during cancer care are lacking. While several observational studies support cannabis use to help ease chemotherapy-related nausea and vomiting, the literature remains more divided on other potential benefits, such as alleviating cancer pain and sleep problems, and some evidence points to potential downsides of cannabis use.

Oncologists should “absolutely talk to patients” about cannabis, Brooke Worster, MD, medical director for the Master of Science in Medical Cannabis Science & Business program at Thomas Jefferson University, Philadelphia, told Medscape Medical News.

“Patients are interested, and they are going to find access to information. As a medical professional, it’s our job to help guide them through these spaces in a safe, nonjudgmental way.”

But, Worster noted, oncologists don’t have to be experts on cannabis to begin the conversation with patients.

So, “let yourself off the hook,” Worster urged.

Plus, avoiding the conversation won’t stop patients from using cannabis. In a recent study, Worster and her colleagues found that nearly one third of patients at 12 National Cancer Institute-designated cancer centers had used cannabis since their diagnosis — most often for sleep disturbance, pain, stress, and anxiety. Most (6src%) felt somewhat or extremely comfortable talking to their healthcare provider about it, but only 21.5% said they had done so. Even fewer — about 1src% — had talked to their treating oncologist.

Because patients may not discuss cannabis use, it’s especially important for oncologists to open up a line of communication, said Worster, also the enterprise director of supportive oncology at the Thomas Jefferson University.

Evidence on Cannabis During Cancer Care

A substantial proportion of people with cancer believe cannabis can help manage cancer-related symptoms.

In Worster’s recent survey study, regardless of whether patients had used cannabis, almost 9src% of those surveyed reported a perceived benefit. Although 65% also reported perceived risks for cannabis use, including difficulty concentrating, lung damage, and impaired memory, the perceived benefits outweighed the risks.

Despite generally positive perceptions, the overall literature on the benefits of cannabis in patients with cancer paints a less clear picture.

The ASCO guidelines, which were based on 13 systematic reviews and five additional primary studies, reported that cannabis can improve refractory, chemotherapy-induced nausea or vomiting when added to guideline-concordant antiemetic regimens, but that there is no clear evidence of benefit or harm for other supportive care outcomes.

The “certainty of evidence for most outcomes was low or very low,” the ASCO authors wrote.

The ASCO experts explained that, outside the context of a clinical trial, the evidence is not sufficient to recommend cannabis or cannabinoids for managing cancer pain, sleep issues, appetite loss, or anxiety and depression. For these outcomes, some studies indicate a benefit, while others don’t.

Real-world data from a large registry study, for instance, have indicated that medical cannabis is “a safe and effective complementary treatment for pain relief in patients with cancer.” However, a 2src2src meta-analysis found that, in studies with a low risk for bias, adding cannabinoids to opioids did not reduce cancer pain in adults with advanced cancer.

There can be downsides to cannabis use, too. In one recent study, some patients reported feeling worse physically and psychologically compared with those who didn’t use cannabis. Another study found that oral cannabis was associated with “bothersome” side effects, including sedation, dizziness, and transient anxiety.

The ASCO guidelines also made it clear that cannabis or cannabinoids should not be used as cancer-directed treatment, outside of a clinical trial.

Talking to Patients About Cannabis

Given the level of evidence and patient interest in cannabis, it is important for oncologists to raise the topic of cannabis use with their patients.

To help inform decision-making and approaches to care, the ASCO guidelines suggest that oncologists can guide care themselves or direct patients to appropriate “unbiased, evidence-based” resources. For those who use cannabis or cannabinoids outside of evidence-based indications or clinician recommendations, it’s important to explore patients’ goals, educate them, and try to minimize harm.

One strategy for broaching the topic, Worster suggested, is to simply ask patients if they have tried or considered trying cannabis to control symptoms like nausea and vomiting, loss of appetite, or cancer pain.

The conversation with patients should then include an overview of the potential benefits and potential risks for cannabis use as well as risk reduction strategies, Worster noted.

But “approach it in an open and nonjudgmental frame of mind,” she said. “Just have a conversation.”

Discussing the formulation and concentration of tetrahydrocannabinol (THC) and cannabidiol (CBD) in products matters as well.

Will the product be inhaled, ingested, or topical? Inhaled cannabis is not ideal but is sometimes what patients have access to, Worster explained. Inhaled formulations tend to have faster onset, which might be preferable for treating chemotherapy-related nausea and vomiting, whereas edible formulations may take a while to start working.

It’s also important to warn patients about taking too much, she said, explaining that inhaling THC at higher doses can increase the risk for cardiovascular effects, anxiety, paranoia, panic, and psychosis.

CBD, on the other hand, is anti-inflammatory, but early data suggest it may blunt immune responses in high doses and should be used cautiously by patients receiving immunotherapy.

Worster noted that as laws change and the science advances, new cannabis products and formulations will emerge, as will artificial intelligence tools for helping to guide patients and clinicians in optimal use of cannabis for cancer care. State websites are a particularly helpful tool for providing state-specific medical education related to cannabis laws and use, as well, she said.

The bottom line, she said, is that talking to patients about the ins and outs of cannabis use “really matters.”

Worster disclosed that she is a medical consultant for EO Care.

Sharon Worcester, MA, is an award-winning medical journalist based in Birmingham, Alabama, writing for Medscape Medical News, MDedge, and other affiliate sites. She currently covers oncology, but she has also written on a variety of other medical specialties and healthcare topics. She can be reached at sworcester@mdedge.com or on X @SW_MedReporter.