Despite impressive advances in cancer treatments in the last few decades, breast cancer remains the most common type of cancer worldwide. Treatment options for solid cancers have been traditionally limited to a combination of chemotherapy, surgery, and/or radiation.
Emerging research has led to the introduction of more effective (and often less toxic) immune-modulating and personalized treatments based on each type of cancer’s unique biology. The emphasis on lower toxicity and more easily accessible treatments has also led to a groundswell of interest in using cannabis to treat and alleviate cancer that’s largely been driven by anecdotal evidence from individual users.
Though cannabis has commonly been used illicitly by cancer patients and others for decades, very little commissioned research has gone into cannabinoids and endocannabinoids because of persistent legal challenges and stubborn stigma around cannabis use worldwide. Fortunately, with time and an increasingly vocal public, governments around the world are relenting and permitting more extensive research about cannabis, the endocannabinoid system, and their complex interactions and implications on inflammation and oxidative stress — both of which have been implicated with potential cancer links.
Here’s some of what the recent science says about cannabis and breast cancer, and a few studies offering symptom relief by adding cannabis to traditional treatments.
In Vitro Anti-tumor Activity
Due to restrictions on the research of cannabis, our knowledge base on the anti-tumor effects of cannabis is mostly limited to animal and lab data. But the current evidence is not without intriguing results that cancer researchers will hopefully someday unlock and be able to apply clinically.
Both anandamide (AEA), an endocannabinoid, and tetrahydrocannabinol (THC), an exogenous cannabinoid, have been shown to directly induce cell death in breast cancer cells. At the same time, cannabidiol (CBD) has shown evidence of promoting the cascade that leads to cell death, both according to this 2021 study of hormone-sensitive breast cancer cells.
On the other hand, a review of 14 years of data found a concerning link between increased breast cancer incidence (BCI) in areas where legal medicinal and recreational cannabis is more readily available and acceptable. Although this study was retrospective, the findings support the existing evidence that cannabis can be genotoxic in several other cancers and can cause birth defects in certain conditions.
This is by no means a comprehensive review of all the research but rather highlights the lack of solid and conclusive evidence. The mixed results for and against the use of cannabis in the treatment of breast cancer support the need for a better understanding of the complexity of cancer, the endocannabinoid system, and cannabis.
Common Challenges in Cancer Treatments
Chemotherapy-induced nausea and vomiting
One of the most common symptoms associated with cancer treatments is chemotherapy-induced nausea and vomiting (CINV), which in extreme cases can lead to malnutrition, severe weight loss, and metabolic imbalances. Cannabis has been used anecdotally to treat the side effects of cancer treatments for decades, and more recent high-quality studies have shown THC to be quite effective in reducing nausea, vomiting, anxiety, and pain and in improving poor appetite associated with chemotherapy.
Commercial preparations of cannabis like dronabinol and nabilone, were approved in the mid-80s for cancer chemotherapy-related side effects. The most common adverse effect of cannabis when treating CINV in this study was the psychogenic or “high” feeling often associated with THC consumption. New strains, hybrids, and more tailored ratios of THC and CBD have greatly improved this unpleasant side-effect while also mitigating CINV.
Chemotherapy-induced peripheral neuropathy
Another distressing and known side-effect of cancer treatments is chemotherapy-induced peripheral neuropathy (CIPN) which is more than just unpleasant numbness and tingling. Over 60% percent of patients receiving chemotherapy will experience CIPN and it’s the most common reason for early discontinuation or dose reduction of treatment, which can reduce the efficacy of treatments overall.
Prevention and treatment of CIPN is very limited outside of pain relievers and cooling garments. Rarely, CIPN can cause permanent damage to peripheral nerves leading to long-term, debilitating neuropathy and a significant reduction in quality of life.
However, a study out of Israel in 2021 found that patients who were exposed to cannabis before or during chemotherapy had 50% less peripheral neuropathy than the control group. Also discovered were potential protective effects of exposure to cannabis prior to chemotherapy treatment: 76% of patients with prior cannabis exposure had less pronounced CIPN, versus 46% of those who initiated cannabis after starting treatment.
Another retrospective study in California reported that most patients using topical cannabis preparations (THC, CBD, or both) had a reduction in CIPN symptoms and suggests the mechanism lies in the endocannabinoid receptors, especially CB1 and CB2, and the intrinsic pain response. A randomized placebo-controlled trial is planned to confirm these results.
These impressive results suggest that with more research and a better understanding of the mechanism we might soon develop cannabis-based options to prevent CIPN, leading to better tolerability of chemotherapy, allowing completion of treatments, and leading to overall better outcomes.
Whether using cannabis as an adjunct to treating breast cancer by supporting the body’s immune regulation or as an amelioration of the side effects of toxic cancer treatments, this area of cancer research clearly deserves more attention.
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Disclaimer Information on this article is provided for informational purposes only and is not meant to substitute for the advice provided by your own physician or another medical professional.