‘Sound evidence base’ needed amid growing acceptance of cannabis for patients with cancer
Medical cannabis is now legal in 33 states, most of which consider cancer a qualifying condition for its use in symptom palliation.
With the legalization of medical cannabis has come increased acceptance of its use among patients, clinicians and the general public.
Nearly a quarter of patients with cancer report current cannabis use, and 90% of cancer survivors view cannabis as potentially beneficial for managing symptoms and support its legalization, according to data cited by Shannon Nugent, PhD, assistant professor in the department of psychiatry at Oregon Health & Science University, and colleagues in a commentary published in Cancer.
Clinicians have begun to incorporate medical cannabis into their cancer care regimens. According to Nugent and colleagues, studies have shown that about 80% of oncologists reported discussing medical cannabis with their patients, with 46% recommending its use, the commentary states. However, approximately 70% of these oncologists reported being inadequately educated about the use of medical cannabis.
“I don’t think physician education has been able to keep up with the rapidly changing social and policy landscape and increased use of cannabis,” Nugent told Healio. “There appears to be a disconnect between the legal status of medical cannabis, high acceptance of cannabis by patients, moderate acceptance of cannabis by clinicians, and the limited evidence base about its safety and efficacy.”
Nugent spoke with Healio about a recent study that showed cannabis to be ineffective for managing cancer-associated pain, as well as concerns about the safety of cannabis use among patients with cancer and the need for further research.
Question: Is the increased use of medical cannabis driven mostly by its legalization?
Answer: Data suggest that public acceptance of medical cannabis and use among individuals with cancer are increasing. We hypothesized that these factors may be contributing to more use among those with cancer — and that many of these decisions are taking place outside the context of medical consultation — but we don’t think we know that with certainty.
Q: Do you think current evidence on medical cannabis is adequate to warrant its widespread use?
A: As we noted in our commentary, the high acceptance of medical cannabis among patients and clinicians does not seem to be supported by the evidence. Approximately 75% of individuals with cancer who use cannabis use it for symptom management, most commonly pain, nausea and sleep disruption. However, the evidence base supporting benefit for most of these symptoms is insufficient. Several recent systematic reviews have found no benefit for pain. There is some evidence for the antiemetic properties of pharmaceutically prepared synthetic cannabis — nabilone or dronabinol.
Q: What are some of the health and safety concerns regarding medical cannabis use?
A: There are many potential adverse events, including potential drug-drug interactions with cancer therapies. In addition, cannabis use is associated with other acute medical, mental health and safety risks, including increased risk for motor vehicle accidents, manic episodes and psychosis, as well as small negative effects on cognitive functioning among frequent users. Finally, although there is a body of in vivo and in vitro laboratory evidence to suggest possible mechanisms for the antitumor properties of cannabis, such as induction of apoptosis and prevention of tumor cell proliferation, these findings have not been translated to humans. We assert that endorsement of medical cannabis for purported anti-neoplastic properties or in lieu of FDA-approved cancer treatments is potentially dangerous.
Q: Do you think studies that show questionable or unfavorable results with cannabis among patients with cancer will — or should — have an impact on its future use?
A: Yes, this information should be disseminated to clinicians and to the public so they can have informed discussions and make informed decisions. There are several initiatives to disseminate what we currently know, in order to close this educational gap. However, more information, as well as a sound evidence base from which to educate, is needed. – by Jennifer Byrne
References:
Nugent S, et al. Cancer. 2019;doi:10.1002/cncr.32732.
For more information:
Shannon Nugent, PhD, can be reached at Oregon Health & Science University, 3181 S.W. Sam Jackson Park Road, Portland, OR 97239-3098.
Disclosure: Nugent reports no relevant financial disclosures.
Perspective
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Interest in medical cannabis for people with cancer is growing rapidly. While changing attitudes toward cannabis rather than solid data largely are driving this interest, patients with cancer often self-report that cannabis — both medical and recreational — is effective for managing a range of their symptoms.
Notably, patients often are the ones initiating the conversation about medical cannabis with their doctors, yet a major knowledge gap persists among physicians. A small percentage of oncologists who have discussed medical cannabis with patients feel adequately educated about it.
This is due, in part, to the ongoing absence of rigorous randomized controlled trial data, which we absolutely need more of in order to effectively advise our patients about their options for symptom palliation. The ability to study marijuana remains highly constrained in the U.S., where it continues to be regulated as a Schedule I drug. Hemp-derived cannabidiol (CBD) has been descheduled, but its legality is still in limbo.
Progress is being made despite these barriers. For example, two double-blind randomized clinical trials — COALA-T at Lankenau Medical Center in the Philadelphia area, and the PINC Study at Columbia University in New York — are investigating the use of CBD-dominant cannabis products to treat chemotherapy-induced peripheral neuropathy (CIPN).
Although the FDA will not allow the study of concurrent cannabis use to prevent or treat symptoms during chemotherapy, many patients report the use of cannabis during active treatment. Our recent observational study of patients with breast cancer — which included those of all ages and disease stages — showed high interest in the use of cannabis to treat multiple symptoms, most commonly anxiety, insomnia and pain.
In the absence of solid data from randomized clinical trials, a meta-analysis is a relatively fast way to shed light. A meta-analysis by Boland and colleagues showed nabiximols (Sativex, GW Pharmaceuticals) was ineffective for treating pain in a very heterogeneous population of patients with advanced/metastatic cancer. Although pain is a complex symptom due to both the cancer and/or the side effects from its treatment, there are common and predictable pain syndromes among people with cancer — such as musculoskeletal pain from aromatase inhibitors or CIPN — for which many patients report improvement from cannabis. In addition, nabiximols — which is not available in the U.S. — is a regulated pharmaceutical product that contains a 1:1 combination of tetrahydrocannabinol and CBD extracts derived from marijuana. In contrast, nonpharmaceutical whole plant-derived marijuana and hemp products contain additional active ingredients and are highly variable, taken in a wide range of doses and through various methods of delivery, with inconsistent quality standards. For these reasons, the results of this meta-analysis has limited application in the U.S. and outside the pharmaceutical arena.
Despite the limitations of a meta-analysis, it is a feasible research approach in an area that is otherwise still very difficult to investigate. But to best understand the role of cannabis in the care of patients with cancer, we clearly need more research on safety, potential interactions with cancer therapies, and differences between delivery methods and dosing.
Providers need to clearly explain to their patients that we only have limited efficacy data on medical cannabis, and those of us who are able to certify patients for medical cannabis in state programs need to be judicious about patient selection, and clear about the health and safety concerns associated with certain cannabis products, especially those that are inhaled. But patient interest in medical cannabis is not going away anytime soon, so it is incumbent upon health care providers to educate ourselves and our patients for a positive shared decision-making process. Otherwise, they are likely to make these decisions without us, obtain inferior and potentially unsafe recreational cannabis products, and consume them through potentially hazardous delivery methods.
References:
Boland EG, et al. BMJ Support Palliat Care. 2020;doi:10.1136/bmjspcare-2019-002032.
Hibbs J, et al. Abstract P5-09-02. Presented at: San Antonio Breast Cancer Symposium; Dec. 10-14, 2019; San Antonio
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