Cancer & Chemotherapy

The Qualifying medical condition stated under the Utah Medical Cannabis Act in Utah Health Code 26-61-104 include: 

Cancer

Summary: There is substantial evidence to support the conclusion that medical cannabis or cannabinoids are effective in the treatment of chemotherapy-induced nausea and vomiting

Chemotherapy-induced Nausea and Vomiting

Summary: There is substantial evidence to support the conclusion that cannabinoids are effective for the treatment of chemotherapy-induced nausea and vomiting (CINV). This is based on supportive findings from good-quality studies with very few or no credible opposing findings.

• Guidance on the Suggested Use of Medical Cannabis – Cancer and Chemotherapy-Induced Nausea and Vomiting

Chemotherapy-induced Nausea and Vomiting

A 2016 Cochran review of 23 randomized controlled trials looking at cannabinoids for the treatment of CINV found that fewer people who received cannabis-based medicines experienced nausea and vomiting than people who received a placebo (Smith et al., 2015). The proportion of people who experienced nausea and vomiting who received cannabis-based medicines was similar to conventional anti-nausea medicines. However, more people experienced side effects on cannabis-based medicines, such as 'feeling high,' dizziness, sedation, and dysphoria, compared with either placebo or other anti-nausea medicines. In cross-over trials where people received cannabis-based medicines and conventional medicines, overall, people preferred cannabis-based medicines.

Meta-analysis of trials using dronabinol (synthetic THC) suggests that low-moderate dosing of THC (7mg/m2) to prevent CINV may be more effective than higher doses of THC or attempting to treat CINV once it is established (Plasse et al., 1991). 

Cancer

There is limited evidence to support the conclusion that medical cannabis or cannabinoids may effectively treat pain due to complications from an invading neoplasm. A 2010 randomized double-blinded placebo-controlled study involving 177 patients with inadequately managed cancer pain despite appropriate use of opioids showed that the use of orally-administered chemotype II medical cannabis extract resulted in a significant reduction in pain compared to placebo. Use of chemotype I (THC-predominant) medical cannabis extract with little or no CBD for treating cancer-related pain was not statistically different from the placebo (Johnson et al., 2010). 

There is insufficient evidence to support or refute the conclusion that medical cannabis or cannabinoids may be effective in treating neuropathic pain due to nerve damage from chemotherapy. Although medical cannabis has been shown to be effective in the relief of pain due to peripheral neuropathy from other causes, there is only one small crossover placebo-controlled trial involving 16 patients that used nabiximols oral-mucosal spray in the treatment of pain due to peripheral neuropathy caused by chemotherapy. Overall neuropathic pain scores in this study were not statistically different between active treatment and placebo, but 5 of the 16 patients had a significant reduction in reported pain with active treatment. (Lynch et al., 2014). 

There is insufficient evidence to support or refute the conclusion that medical cannabis is effective in the treatment of cancer-associated cachexia (see the Persistent Nausea, Vomiting/Cachexia section above). 

There is insufficient evidence to support the conclusion that medical cannabis or cannabinoids are effective or ineffective for the general treatment of malignant neoplasms in humans (National Academies of Sciences, Engineering, and Medicine, 2017d). There is, however, an increasing body of preclinical in vitro and animal-model data suggesting direct anticancer effects of cannabinoids in some types of cancer (Rocha et al., 2014). Accumulating evidence from these vitro and/or pre-clinical studies suggests that antineoplastic effects of cannabinoids occur via dysregulation of the endocannabinoid system (Velasco et al., 2016 & Pisanti et al., 2009).

Elevated levels of endocannabinoids and their receptors (CB1 and CB2) have been observed in a number of cancers (lymphomas, hepatocellular carcinoma, leukemia, glioma, and pancreatic, prostate, and breast cancers). In some cases, increased expression of the cannabinoid receptors correlated with disease severity (Velasco et al., 2016). 

The exact mechanism through which cannabinoids exert antineoplastic effects is not known, but in vitro data suggest that cannabinoids induce cancer cell apoptosis (Velasco et al., 2016). Cannabinoids may also inhibit tumor angiogenesis and limit cancer cell migration and metastasis (Velasco et al., 2016). Cannabidiol has been shown to specifically inhibit cancer cell invasiveness in various preclinical animal models (Velasco et al., 2016). Caution is advised, however, as less frequently, tumor-promoting effects have also been described (Hart et al., 2004 & Cudaback et al., 2010). The reason for this conflict is unknown, but it may be related to the achieved concentration of cannabinoids, the expression level of cannabinoid receptors, or the immunosuppressive effects of cannabinoids (Pisanti et al., 2009 & Hart et al., 2004 & Cudaback et al., 2010). Antineoplastic properties of cannabinoids in vitro have typically been observed at very high doses that may not be achieved in clinical practice (Health Canada, 2018). The efficacy of cannabinoids as antitumor agents has not been sufficiently studied in clinical studies. The limited existing clinical studies of cannabinoids have been for the treatment of recurrent glioblastoma multiforme (GBM), an aggressive primary brain tumor with a poor prognosis (Guzman et al., 2006 & GW Pharmaceuticals, 2017).

Case reports describing patient-administered inhaled cannabis (among two children with pilocytic astrocytomas) or orally administered hemp oil (in one child with terminal acute lymphoblastic leukemia [ALL]) reported a regression in tumors and reduction in blast cell counts, respectively, during the time period of administration of the cannabinoids (Foroughi et al., 2011 & Singh et al., 2013). In phase I/II trial involving 9 patients with GBM that had failed standard therapies, including surgery, external-beam radiotherapy, and in 2/9 patients adjuvant chemotherapy, Δ9 THC was administered intracranially directly into the tumor via a catheter that was surgically placed during a second surgery. The THC was infused on a daily basis for up to 10 days per cycle, and some patients received multiple cycles (up to 6). Overall intracranially administered THC was well tolerated; one patient had a mild episode of bulimia, hypothermia, and euphoria that resolved. All patients experienced cerebral edema, which is typical after a craniotomy. Median survival was approximately 24 weeks, and two patients survived for >one year (Guzman et al., 2006). Additional studies of cannabis (the nabiximols oromucosal spray, Sativex) for recurrent or newly diagnosed GBM are underway (GW Pharmaceuticals, 2017). 

NOTE: Open discussion should be encouraged between healthcare providers and patients regarding the potential use of medical cannabis in Cancer Mangement, symptoms due to cancer, and side-effects of chemotherapy. Some patients may consider the use of cannabis outside of the recommendations of their oncology team (Abrams, 2016). The decision to use cannabis or medical cannabis for the management of chemotherapy side-effects, pain, or primary treatment/palliative treatment of a malignant neoplasm should generally be made through consultation with an oncology professional who is able to explore all potential treatment options with the patient.