Approaching Conversations About Cannabis Use with Patients & Caregivers

Nearly half of adults with cancer in North America use cannabis—and often with limited clinician awareness. Even when patients do share their use, oncologists are limited in offering evidence-based guidance. That's why a team of experts developed the Cannabis and Cannabinoids in Adults With Cancer: American Society of Clinical Oncology (ASCO) Guideline (JCO 2024; doi.org/10.1200/JCO.23.02596). At the 2025 ASCO Annual Meeting, guideline authors Ilana Monica Braun, MD, at Dana-Farber Cancer Institute; Eric Roeland, MD, FAAHPM, FASCO, Associate Professor of Medicine in the Division of Hematology/Medical Oncology at Knight Cancer Institute; and Ishwaria M. Subbiah, MD, FASCO, MS, Executive Director of Cancer Care Equity & Professional Wellness at Sarah Cannon Research Institute, presented composite cases and key recommendations to help oncologists engage in discussions about cannabis with patients and caregivers. Need for High-Quality Clinical Research Access to cannabis has grown faster than the clinical research to support its use, the panelists said. Yet many adults with cancer seek out these products anyway. “Your patients will pursue holistic options, with or without your approval or your permission, so it's your job to understand that fact and be prepared to address it,” said Stacy Blanky, the patient advocate on the panel. When Stacy was diagnosed with lymphoma at age 27, she obtained a medical marijuana license in New York to access cannabis products to help with nausea, appetite, and sleep. Because cannabis is not covered by insurance, the regimen cost her approximately $200 per month. She's not alone. In one patient survey funded by the National Cancer Institute, roughly one in five patients said they use cannabis as part of their cancer journey. “So, the takeaway is that this is not some sidebar in oncology. It's a rather common practice, and that we need to come up with a patient-centered, transparent, evidence-based, compassionate approach,” Braun said. Supporting Clinical Decision-Making The ASCO guidelines acknowledge the potential medicinal role of cannabis and cannabinoids in oncology, while highlighting the limited availability of high-quality evidence. The first recommendation calls for system-level support for oncologists to integrate cannabis into cancer care: ASCO Guideline Rec 1.1: Health systems and clinicians, in partnership, should provide adults with cancer unbiased, evidence-based cannabis and/or cannabinoid educational resources to facilitate clinical communication, informed decision-making, and systematized approaches to care (Good practice statement). The guidelines also invite clinicians to have open, nonjudgmental conversations with patients about cannabis use: ASCO Guideline Rec 1.2: Given the high prevalence of cannabis and/or cannabinoid use among adults with cancer, clinicians should routinely and nonjudgmentally inquire about cannabis use (or consideration of use) and either guide care or direct adults with cancer to appropriate resources (Good practice statement). Many times, patients seek cannabis to help mitigate treatment-related toxicities, improve symptoms, and enhance quality of life, which prompted more guidance: ASCO Guideline Rec 3.1: Adults with cancer who receive moderately or highly emetogenic antineoplastic agents with guideline-concordant antiemetic prophylaxis and experience refractory nausea or vomiting may augment their antiemetic regimen with dronabinol, nabilone, or a quality-controlled oral 1:1 THC:CBD extract (Type: Evidence-based; Evidence quality: Moderate for dronabinol and nabilone, low for 1:1 THC:CBD extract; Strength of recommendation: Weak). “The indication with the greatest evidence base in an oncologic population is chemotherapy-induced nausea and vomiting when guideline concordance prophylaxis fails,” said Braun. For other indications, like mood disturbances, post-traumatic stress disorder, and sleep, “We either have negative evidence, no evidence, or unclear evidence at this time,” she added. “We desperately need more research to be done.” Marijuana is classified as a Schedule I drug under the Controlled Substances Act, indicating a high potential for abuse and no accepted medical use at the federal level. This classification imposes barriers to clinical research. Know the Risks Guidance can be given to patients about risks. Unlike opioids, the guideline authors are not concerned about respiratory depression with cannabis use; however, other side effects, such as orthostatic hypotension and dizziness, particularly in older adults, may still occur. Oncologists also need to consider drug-to-drug interactions, such as with blood thinners, benzodiazepines, and opioids. Higher doses of CBD (300 mg and above, and without THC) can cause reversible elevation of liver enzymes. ASCO Guideline Rec 3.2: Outside of a clinical trial, clinicians should not recommend that adults with cancer use 300 mg or more per day of oral CBD to manage symptom burden due to lack of proven efficacy and risk for reversible liver enzyme abnormalities (Type: Evidence based; Evidence quality: Low; Strength of recommendation: Weak). Cannabis as a Cancer Treatment Other patients may seek cannabis as a cancer treatment. High-potency cannabis pastes are sometimes marketed with an antineoplastic claim with suggestions to titrate high to 100 mg a day of cannabinoids, if not higher. This consumption is something for clinicians to be aware of—and advise against. ASCO Guideline Rec 2.1: Clinicians should recommend against use of cannabis and/or cannabinoids to augment cancer-directed treatment unless in the context of a clinical trial (Type: Evidence based; Evidence quality: Very low; Strength of recommendation: Weak). The guideline authors were so opposed to the use of cannabis as an anti-cancer agent that they issued a second recommendation advising against its use in lieu of standard cancer treatments. ASCO Guideline 2.2: Clinicians should recommend against use of cannabis and/or cannabinoids in place of cancer-directed treatment (Type: Informal consensus; Evidence quality: Very low; Strength of recommendation: Strong). When patients inquire about the role of cannabis in targeting cancer cells, “ask if they are referencing a preclinical trial or a clinical study,” Roeland added. Patients need to understand “the differences between very promising and exciting signals in a preclinical model versus what actually translates into humans,” he said. Impact on Immune Checkpoint Inhibitor Outcomes Cannabis may also impact immune checkpoint inhibitor therapy outcomes. “The current state of evidence doesn't show a definitive association between cannabis and inferior outcomes with immune checkpoint inhibitors,” Subbiah said. But there are preliminary studies that suggest a possible negative survival interaction. “We have not come across a study that shows a positive impact on survival,” she added. “What does this mean for our practice? Education of self in this moment. This is the state of the evidence at this time. We hope this continues to evolve to where we'll have recommendations that move toward more definitive conclusions on the impact.” The ASCO guidelines suggest caution when there isn't conclusive data and when part of the preliminary data suggests a negative interaction, she said. “And then we support patient autonomy. Patients are the ones going through this. And so, the decisions they make, we, as healthcare professionals—even if we don't have a definitive conclusion from the evidence—can support patient autonomy.” CHER Framework to Guide Your Processes To apply these recommendations, the ASCO panelists recommend clinicians use the CHER framework. Clear the stigma: Become familiar with current evidence, relevant laws, and institutional policies. Engage legal counsel and collaborate with stakeholders to develop a clinical integration plan. History gathering: Obtain a cannabis history, including reasons for use, information sources, product, dosage, route, and frequency. Ask about perceived benefits and side effects so you can assess any contraindications with concurrent medications. Education: Talk to patients about potential toxicities: anxiety, paranoia, fatigue and sedation, confusion, dizziness, dry mouth, and more. Recommend: Respect patient autonomy and provide a recommendation. “Even in the absence of evidence, it doesn't mean that you have to give a yay or nay. A firm recommendation would be, ‘there isn't evidence right now,’” Subbiah added. “We truly don't know. We can't predict what will happen, but here are the risks, the benefits. And let's go through the same decision-making we would for really any other medication or treatment.” Erin DiGirolamo is a contributing writer. Cannabis in Cancer Care: Current Evidence & Other Considerations During the Community Oncology Alliance's 2025 Community Oncology Conference, Richard Lee, MD, FASCO, Medical Oncologist at City of Hope Comprehensive Cancer Center, and Donald Abrams, MD, specialist in integrative medicine and cancer treatment at UCSF Osher Center for Integrative Medicine, delivered a comprehensive presentation on the evolving role of cannabis in cancer care. Their discussion provided an evidence-based overview of cannabis use among cancer patients, clinical guidance for oncologists, and an honest look at the limitations of current data.Lee began by highlighting how frequently cancer patients ask about cannabis. “We get a lot of questions as oncologists, asking about the use of different natural products, and also the use of integrative therapies,” he said. While natural products have long been common in complementary care, “maybe the most common question I get these days is about this herb,” he added, referencing cannabis. A National Cancer Institute-funded survey of more than 13,000 patients revealed that nearly two-thirds had used some type of cannabis product (26% before cancer, 26% before and since cancer diagnosis, 6% since cancer diagnosis, and 20% were active users), according to Lee, who was a part of this research initiative. The most common reasons for cannabis use included sleep, pain, mood changes, stress, anxiety, or depression. Scan the QR code to read the full article.