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The quest for quality-of-life: chemotherapy & cannabis

Mitigating side-effects with marijuana
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Cancer sucks!—⁠But often it is the therapy that is causing the most discomfort. Many chemotherapies can have significant side-effects that profundly impact a patient's quality-of-life. Managing those side-effects can be as critical for the success of cancer therapy as the treatment itself. If the side-effects are too severe patients can be left with no choice but to abort the treatment. Therefore a great deal of effort goes into finding tools to improve people's well-being during the chemo. Cannabis has become a more frequently used asset in the cancer patient's toolbox. In this article we will be looking at some of the ways cannabis can mitigate chemotherapy side-effects. But before we move on to that, I strongly urge you to first check out our more general article on cancer because cannabis is not universally compatible with all forms of cancer therapy. You can read more about this here: "What should I know about cannabis and cancer treatments?"

Chemotherapy and quality of life

Managing anti-cancer treatment via chemotherapy is a balancing act. The doctors need to tailor the dosage to maximize the effectiveness of the respective chemotherapy treatment while at the same time minimizing the unwanted side effects that severely impact a patient's quality of life. The most impactful symptoms that need to be managed are :

  • Acute & chronic pain
  • Nausea & vomiting
  • Anorexia & weight loss
  • Depression & mental health issues

Beyond that, sleep disorders, fatigue, cardiovascular problems, gastrointestinal distress all further erode the patient's quality of life. The compounding side-effects progressively worsen until the negative consequences of the treatment outweigh the benefits. Therefore, it is imperative to manage the side effects as much as possible to allow the treatment to continue for as long as necessary. However, nausea and the subsequent risk of vomitting is by far the most common side-effect of chemotherapy.

Chemotherapy-induced nausea and vomiting (CINV)

One of the most common side effects of chemo is chronic nausea and vomiting. Vomiting or "emesis," like the medical experts like to call it, is particularly impactful. It is an exhausting and undignified side-effect that plagues most patients. Luckily, anti- "emetic" drugs exist that are highly effective at preventing emesis, i.e., vomiting. And while that is wonderful, it still leaves somewhere between 40–70% of patients with feelings of nausea. Not as debilitating as full-on vomiting, nausea is still super annoying to deal with. Anecdotally, patients have claimed that cannabis relieves chemotherapy-induced nausea. Indeed there is increasing scientific evidence in support of those anecdotes. The mechanism by which chemotherapy induces nausea and vomiting is well understood, and it gives us insights into how cannabis might be mitigating unwanted side effects. In a nutshell, chemotherapeutic drugs promote the release of excess serotonin by cells that line the GI tract. The serotonin is detected by afferent nerves in the area and transmitted to the brain as a warning of excess chemicals in the GI tract. The brain responds to that signal by initiating vomiting.

A primer on the science behind CINV

Chemotherapy drugs cause enterochromaffin cells of the GI tract to release serotonin. The serotonin binds to 5-hydroxytryptamine 3 (5-HT3) receptors found on local afferent vagal neurons. The signal is transduced to the brain's emetic center, where it is interpreted as "excess chemicals" in the GI tract. Emesis is promoted to remove the perceived toxic threat. Prolonged exposure to chemotherapy agents can further damage the enterochromaffin cells and cause apoptosis. At this point, chronic elevation of serotonin and other signaling molecules leads to sensitization and inflammation of the vagal neurons and causes chronic nausea and vomiting. Anti-emetic drugs acting as 5-HT3 antagonists can be used as an effective treatment option. Cannabidiol (CBD) can act as a modulator of 5-HT3 and an agonist for the 5-HT1A autoreceptor, reducing the availability of serotonin. Additionally, cannabinoids inhibit the signal transduction to the brain by dampening the pre-synaptic release of neurotransmitters and reducing the activity of the emetic center of the brain. 

Cannabis-derived phytocannabinoids reduce the availability of serotonin in the GI tract, inhibit the transduction of the nausea-inducing signal to the brain and alter the perception of the noxious stimulus in the vomiting center in the cerebral cortex. One of the most used cannabinoid-based medications prescribed by doctors is a synthetic THC isomer called dronabinol. Although in severe cases of vomiting administration of cannabinoids via inhalation is a better option. 

The upside of cannabis consumption

Cannabinoids can mitigate nausea and vomiting. But beyond that, chemotherapy patients often experience other quality of life reducing symptoms. Chief among them are various kinds of pain. Depending on where the cancer cells are growing, what organs are affected, and what type of chemotherapy agents are being used. Dose-limiting toxicity of chemotherapy can lead to severe conditions like chemotherapy-induced peripheral neuropathy (CIPN), often followed by cessation of the therapy. The good news is cannabis has analgesic properties, so it helps with pain. Also, the munchies are a quasi cannabis cliche, and since cannabis reduces both feelings of nausea while also stimulating food consumption, it can help with chemotherapy-induced weight loss.

For more specific articles about how cannabis affects various chemotherapy-related symptoms, follow the links below.

References:

  1. Kleckner, Amber S et al. “Opportunities for cannabis in supportive care in cancer.” Therapeutic advances in medical oncology vol. 11 1758835919866362. 1 Aug. 2019, doi:10.1177/1758835919866362
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  6. Makary, Patrick et al. “Patient Counseling Guidelines for the Use of Cannabis for the Treatment of Chemotherapy-Induced Nausea/Vomiting and Chronic Pain.” Journal of pain & palliative care pharmacotherapy vol. 32,4 (2018): 216-225. doi:10.1080/15360288.2019.1598531 https://pubmed.ncbi.nlm.nih.gov/31070496/
  7. Badowski, Melissa E. “A review of oral cannabinoids and medical marijuana for the treatment of chemotherapy-induced nausea and vomiting: a focus on pharmacokinetic variability and pharmacodynamics.” Cancer chemotherapy and pharmacology vol. 80,3 (2017): 441-449. doi:10.1007/s00280-017-3387-5 https://pubmed.ncbi.nlm.nih.gov/28780725/
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