Does medical cannabis have a place in cancer treatment?
Cannabis treatment in oncology has been under thorough investigation recently, particularly in terms of alleviating some of the symptoms of cancer and conventional treatment methods. These areas of potential use include chemotherapy-induced nausea and vomiting, intractable pain, cachexia, and there is also talk of the potential of cannabinoids to inhibit tumours. This article reviews the currently available scientific literature on the use of medicinal cannabis in oncology.
To begin with, the use of cannabis (more specifically, the psychoactive component called THC) for both medicinal and recreational purposes can be associated with the occurrence of mild side effects such as dizziness, euphoria, dry mouth, confusion, and nausea. Another important factor to consider before starting cannabis therapy is how this plant medicine is administered. Generally, it can be administered via oromucosal sprays, capsules, edibles, oils or inhalation of the dry plant matter. It is definitely not recommended to smoke cannabis! For a quick onset of effects, which cancer patients often need, it is advisable to choose a healthy alternative – inhalation of vapours from a device called a vaporizer (two German devices with a medical device certificate are available in many countries).
When using medical cannabis to treat side effects associated with cancer treatment, physicians need to consider possible interactions of cannabinoids with the patient’s conventional therapy. For example, stopping or limiting the body’s immune response may suppress the effectiveness of immunotherapy and weaken the body’s ability to destroy cancer cells. In one study, THC has been found to reduce the proliferation of lymphocytes and their conversion into cytotoxic T-lymphocytes, which are involved in the body’s immune response.
To date, there have been relatively few well-designed, randomised and controlled trials investigating cannabis treatment in patients with cancer pain. However, there has been a growing interest on the part of patients – due to the side effects of opioids and other analgesics (e.g. renal impairment, polypharmacy and risk of addiction) – in the use of cannabis for cancer pain. Although the evidence is not clear-cut, there seems to be a presumption for the successful use of cannabis when standard treatments for all types of pain fail. The evidence is somewhat more convincing in the specific cases of neuropathic and cancer pain, but there are still no uniform conclusions regarding the different routes of administration, dosing and the exact composition of cannabis-based treatments.
Poor quality sleep and lack of sleep are very common problems for cancer patients. At the same time, patients themselves report that one of the most common reasons for using cannabis is to treat their insomnia. However, the research on cannabis use and sleep is rather ambiguous. There is some scientific work suggesting that short-term high doses of CBD may be useful in improving falling asleep and prolonging sleep time – probably thanks to its anxiolytic effect. On the other hand, the results of other studies suggest that discontinuing high THC use may actually cause or worsen insomnia.
Of course, chronic pain has a major impact on the quality and duration of sleep. One study with the oromucosal spray Sativex (THC and CBD in a 1:1 ratio) investigated the potential role of cannabinoids in addressing pain-related sleep disorders. Most subjects in this research reported subjective improvements in sleep quality, although more related to a reduction in pain levels than to changes in biological sleep patterns. Frequent use of cannabis, especially high-THC products, leads to tolerance and may induce self-titration and high-THC use to improve sleep quality.
The first-line treatment of anxiety disorders includes various antidepressants, benzodiazepines and also psychotherapy. Up to 40% of cancer patients still have symptoms of anxiety despite conventional treatment, leading to an interest in alternative forms of therapy. The non-psychoactive cannabinoid CBD has therapeutic potential in the treatment of anxiety, as shown by a growing number of studies and meta-analyses investigating its use in several anxiety disorders, from post-traumatic stress disorder to fear of public speaking.
There are indications that high THC content may exacerbate anxiety in some users or when consumed in excess, induce panic attacks or even induce psychosis in genetically predisposed individuals, while CBD has shown good tolerability and efficacy in the treatment of social anxiety, post-traumatic stress disorder and general anxiety. Both oral and inhaled forms of cannabis with higher concentrations of CBD have proven successful in studies.
Nausea and anorexia
A meta-analysis summarizing 28 studies, most of which were completed before 2000, evaluated synthetic cannabinoids as more effective than placebo or other available antiemetics. Other studies completed more recently also confirm that although patients reported more frequent side effects, they preferred natural cannabinoids to other antiemetics. There are no published studies examining the effect of CBD alone on chemotherapy-induced nausea and vomiting. A review published in 2020 showed that a small number of smoked or inhaled cannabis varieties with CBD present had a positive effect on nausea, but there are currently no consistent data regarding CBD-dominant cannabis preparations on appetite or nausea.
Nevertheless, patients often report a subjective improvement in appetite when taking cannabis. Marinol, as a synthetic analogue of THC, was originally approved for this indication in HIV patients in the 1980s. Studies show that cannabis inhalation increases blood levels of ghrelin and leptin, hormones associated with feelings of hunger. Smaller studies of THC supplementation in patients with advanced cancer have produced subjective reports of improved appetite and cravings.
Preclinical in vitro and in vivo cancer models have repeatedly shown that cannabinoids can modulate tumour growth, although these data are so far considered clinically irrelevant. Similarly, cell and animal studies have repeatedly demonstrated similar anti-tumour effects of plant-derived cannabinoids.
In 2017, the US National Academy of Sciences convened a committee to examine the health effects of cannabis. In evaluating the potential anti-cancer properties for cancer patients, the committee found one systematic review focused specifically on gliomas.
The review identified a total of 2 260 studies, of which 35 met the inclusion criteria and all were pre-clinical (except for one small clinical trial); all 16 in vivo studies described an anti-cancer effect of cannabinoids. The Committee concluded that there was insufficient evidence to support or refute the conclusion that cannabinoids are an effective treatment for cancer (including glioma), adding that the signals from preclinical research should prompt proper clinical trials. Unfortunately, these are still not available.
Cannabis therapy in inexperienced (cannabinoid naive) cancer patients should start with low doses of non-inhaled products, possibly with a higher CBD content or a CBD:THC ratio of 1:1 with a slow increase in THC according to the specific indication and tolerability. Patients who have previous experience with cannabis may be able to tolerate higher THC concentrations. Dosing of oral or sublingual products should not start with doses higher than 5 mg THC in inexperienced users. CBD dosing can be more liberal and is generally well tolerated.
*The above text was written by an independent contributor and does not reflect the official views of Motagon or the guidelines for the use of Motagon products.