PURPOSE: To guide clinicians, adults with cancer, caregivers, researchers, and oncology institutions on the medical use of cannabis and cannabinoids, including synthetic cannabinoids and herbal cannabis derivatives; single, purified cannabinoids; combinations of cannabis ingredients; and full-spectrum cannabis. METHODS: A systematic literature review identified systematic reviews, randomized controlled trials (RCTs), and cohort studies on the efficacy and safety of cannabis and cannabinoids when used by adults with cancer. Outcomes of interest included antineoplastic effects, cancer treatment toxicity, symptoms, and quality of life. PubMed and the Cochrane Library were searched from database inception to January 27, 2023. ASCO convened an Expert Panel to review the evidence and formulate recommendations. RESULTS: The evidence base consisted of 13 systematic reviews and five additional primary studies (four RCTs and one cohort study). The certainty of evidence for most outcomes was low or very low. RECOMMENDATIONS: Cannabis and/or cannabinoid access and use by adults with cancer has outpaced the science supporting their clinical use. This guideline provides strategies for open, nonjudgmental communication between clinicians and adults with cancer about the use of cannabis and/or cannabinoids. Clinicians should recommend against using cannabis or cannabinoids as a cancer-directed treatment unless within the context of a clinical trial. Cannabis and/or cannabinoids may improve refractory, chemotherapy-induced nausea and vomiting when added to guideline-concordant antiemetic regimens. Whether cannabis and/or cannabinoids can improve other supportive care outcomes remains uncertain. This guideline also highlights the critical need for more cannabis and/or cannabinoid research. Additional information is available at www.asco.org/supportive-care-guidelines .

Cannabis species have been used as medicine for thousands of years; only since the 1940s has the plant not been widely available for medical use. However, an increasing number of jurisdictions are making it possible for patients to obtain the botanical for medicinal use. For the cancer patient, cannabis has a number of potential benefits, especially in the management of symptoms. Cannabis is useful in combatting anorexia, chemotherapy-induced nausea and vomiting, pain, insomnia, and depression. Cannabis might be less potent than other available antiemetics, but for some patients, it is the only agent that works, and it is the only antiemetic that also increases appetite. Inhaled cannabis is more effective than placebo in ameliorating peripheral neuropathy in a number of conditions, and it could prove useful in chemotherapy-induced neuropathy. A pharmacokinetic interaction study of vaporized cannabis in patients with chronic pain on stable doses of sustained-release opioids demonstrated no clinically significant change in plasma opiates, while suggesting the possibility of synergistic analgesia. Aside from symptom management, an increasing body of in vitro and animal-model studies supports a possible direct anticancer effect of cannabinoids by way of a number of different mechanisms involving apoptosis, angiogenesis, and inhibition of metastasis. Despite an absence of clinical trials, abundant anecdotal reports that describe patients having remarkable responses to cannabis as an anticancer agent, especially when taken as a high-potency orally ingested concentrate, are circulating. Human studies should be conducted to address critical questions related to the foregoing effects.

Cannabis is currently available for medicinal use in 33 states and the District of Columbia.¹ Pain is the principle reason individuals report for accessing cannabis from dispensaries nationwide.² A report by the National Academies of Sciences, Engineering and Medicine³ cited pain as the therapeutic indication with the strongest evidence base in the published medical literature. However, little data from controlled human clinical trials are currently available to support the widespread use of medicinal cannabis in painful conditions, including sickle cell disease (SCD).

As medical cannabis becomes legal in more states, cancer patients are increasingly interested in the potential utility of the ancient botanical in their treatment regimen. Although eager to discuss cannabis use with their oncologist, patients often find that their provider reports that they do not have adequate information to be helpful. Oncologists, so dependent on evidence-based data to guide their treatment plans, are dismayed by the lack of published literature on the benefits of medical cannabis. This results largely from the significant barriers that have existed to effectively thwart the ability to conduct trials investigating the potential therapeutic efficacy of the plant. This is a narrative review aimed at clinicians, summarizing cannabis phytochemistry, trials in the areas of nausea and vomiting, appetite, pain and anticancer activity, including assessment of case reports of antitumor use, with reflective assessments of the quality and quantity of evidence. Despite preclinical evidence and social media claims, the utility of cannabis, cannabinoids or cannabis-based medicines in the treatment of cancer remains to be convincingly demonstrated. With an acceptable safety profile, cannabis and its congeners may be useful in managing symptoms related to cancer or its treatment. Further clinical trials should be conducted to evaluate whether the preclinical antitumor effects translate into benefit for cancer patients. Oncologists should familiarize themselves with the available database to be able to better advise their patients on the potential uses of this complementary botanical therapy.