Understanding the Role of Cannabis in Cancer Care: An Emerging Priority

With the legalization of medicinal cannabis across most states within the United States, in Canada, and elsewhere in the world over the last 3-5 years, cannabis use in both the general patient population and among cancer survivors is expected to rise.¹ Within the United States, cancer is one of the most frequent conditions that qualifies a patient for access to medicinal cannabis.² In a prior study evaluating the use of cannabis in patients with cancer from 2015 to 2016 in a legalized state, up to 24% of patients reported using cannabis, most commonly for physical symptoms (75%), neuropsychiatric symptoms (63%), and recreational use (35%).³ Despite the current and projected rise in cannabis use in cancer care over the next decade, to our knowledge, the few studies to date evaluating cannabis use in the oncology setting have primarily focused on its role in symptom control and supportive care.^4-8

The articles that accompany this commentary cover a range of important emerging topics related to the use of cannabis in the cancer care setting including a clinical review of cannabis use and evidence for its indications in cancer care, the perceived knowledge and formal training on medical cannabis among oncology trainees, the background and training of personnel working in cannabis dispensaries, and a characterization of patients presenting at a pharmacy-led cannabis consultation service at a cancer center.^1,2,8,9 These articles help provide information on the current practice and care delivery patterns of cannabis in cancer care but also help us to begin asking new research questions in this evolving area.

As described in the clinical review of cannabis by Worster et al,⁸ there are multiple formulations of cannabis with the most common two being tetrahydrocannabinol and cannabidiol with different forms of administration which vary with respect to pharmacokinetics and downstream side-effect profiles. The most common indications with some evidence include pain, insomnia, anxiety, nausea, and anorexia, but, to our knowledge, the evidence is limited because of both a lack of studies and mixed results seen to date. Furthermore, cannabis has been showed to be potentially immunosuppressive among patients receiving immune checkpoint inhibitors where it reduces response rates but also reduces risk for immune-related adverse events. It has showed potential tumor growth modulating effects in early preclinical studies.⁸ Despite these studies, more research is required to understand how cannabis can affect both cancer- and treatment-related symptoms but also how it may interact with and affect outcomes with different cancer treatment modalities including systemic therapy and radiation therapy. From previous studies with tobacco, tobacco has been associated with effects on both outcomes and toxicities across the different cancer treatment modalities including surgery, radiation therapy, and systemic therapy and cannabis use may have similar effects.¹⁰ Developing a better understanding of which types and formulations of cannabis may interact with different cancer treatment options will help guide treatment decision making for cancer supportive care. With the increase in cannabis use across both the general and cancer patient populations, we anticipate that further observational studies will be completed in cancer patient subgroups, which will help us better understand how cannabis may influence both treatment- and cancer-related outcomes. Further studies including clinical trials may start to evaluate the role of medicinal cannabis in cancer supportive care, which will in turn allow us to better understand which symptoms and outcomes cannabis may help to improve or benefit.

In addition to the lack of evidence supporting treatment decisions for cannabis use, many oncology care providers may not be well prepared to help make clinical recommendations regarding cannabis use. Patell et al² surveyed oncology fellows across the United States on their perceived knowledge and training regarding cannabis use. Although the majority have had discussions about cannabis with patients, only a quarter felt they had received formal training in medical cannabis and 13% felt sufficiently knowledgeable about cannabis to make clinical recommendations. There were mixed opinions regarding its potential benefit on cancer-related symptoms and common themes from open-ended responses included the lack of strong clinical data supporting cannabis and lack of training on cannabis use. Similar findings were seen among cannabis dispensary personnel in the United States. Braun et al⁹ conducted semistructured interviews with both client-facing and managerial personnel working at cannabis dispensary and identified that although many personnel were passionate about their profession, many of the participants felt that the most desirable hiring qualities related toward customer service qualities. Although half of interviewees reported using cannabis experience as a hiring quality, this meaning varied from personal experience with cannabis to having knowledge in cannabis therapeutics. Workplace cannabis therapeutics training at dispensaries was felt to be nonstandardized and weak, with many employees seeking other means to gain cannabis knowledge including self-directed learning and peer-to-peer learning on the job. Both studies suggest that cannabis care providers, in terms of clinicians and dispensaries, do not feel adequately trained to make clinical recommendations regarding cannabis therapeutics, and standardized provider education and training in cannabis therapeutics is recommended. However, content for developing this training might be limited in part because of the current lack of strong clinical evidence regarding the use of cannabis in cancer care.⁸ We anticipate that as further studies on cannabis in the cancer care are completed, there will be additional recommendations regarding its use that will help to inform the development and creation of training modules for both oncology practitioners and cannabis dispensary staff. As cannabis use is becoming more prevalent, oncologists should receive some formalized training in cannabis therapeutics, and standardized training should be required for cannabis dispensary staff, of which many are often privately owned. This will in turn better allow providers to help patients make informed decisions regarding using cannabis in their cancer care.

Finally, newer models for cannabis use in cancer care have been developed. Marchese et al¹ describe their experience with a pharmacist-led cannabis clinic embedded in a tertiary cancer care center. Among referrals, medicinal cannabis was supported as a treatment option in only half of patients and common reasons for not supporting cannabis use included lack of indication, requiring alternative prior first-line treatment, and potential drug interactions. Only half the patients for whom medicinal cannabis was indicated who then received access ultimately started treatment with cannabis. This model of care highlights the importance of ongoing patient education and guidance around the use of cannabis in cancer care despite limitations in evidence and recommendations to date, to our knowledge, and the potential role for pharmacists in the provision of care for patients with cancer considering cannabis use.

In summary, cannabis use is expected to continue to rise among both patients with cancer and in the general population. Further high-quality studies (both observational studies and interventional trials) are required to help understand how cannabis use may affect cancer outcomes, interact with cancer treatments, and help to identify indications for cannabis use in cancer supportive care. Specific key questions include the following: (1) Which symptoms are best treated using cannabis and using which cannabis formulations? (2) How does cannabis (and its various formulations) interact with our current cancer therapies (including systemic therapy, surgery, and radiation therapy) and other supportive care medications used in cancer care? (3) What are the risks and potential side effects or toxicities of cannabis use in cancer care? These studies will help to develop the evidence base, which will allow us to better train both front-line clinicians and cannabis dispensary staff on cannabis therapeutics in cancer care and form the basis for patient education material on cannabis use in cancer care. Newer models of care for cannabis may be developed and involve other allied health members including pharmacists who may play an important role in counseling patients regarding cannabis use. Given the current lack of strong evidence supporting routine use of cannabis in cancer care and the increasing percentage of patients with cancer both using and inquiring about cannabis use, we recommend clinicians educate themselves on what is currently known and unknown on the benefits and risks of cannabis use in cancer care to assist patients in deciding about using cannabis as part of their cancer care. We anticipate that as additional studies are completed in this evolving area, we will be able to identify how to best integrate medicinal cannabis into cancer supportive care and assist patients in shared decision making regarding the use of cannabis as part of their cancer care.

AUTHOR'S DISCLOSURES OF POTENTIAL CONFLICTS OF INTEREST

Understanding the Role of Cannabis in Cancer Care: An Emerging Priority

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