Cannabis and Colorectal Cancer: What the Research Says

Colorectal cancer includes cancer that starts in the large bowel (colon cancer) and cancer that begins in the rectum (rectal cancer). Colorectal cancer is also sometimes called “bowel cancer.” However, these two cancers are often grouped and have similar symptoms (a change in bowel movements, blood in the stool, weight loss, and fatigue), where the cancer starts can make a difference to outcomes and treatment.

Colorectal cancer is expected to cause 52,580 deaths in 2022 and is the third leading cause of cancer-related deaths in men and women in the US. As of 2017, the five-year survival rate in the US is around 65%. Men and African-Americans are at a higher risk of developing colorectal cancer than those suffering from an inflammatory bowel disease (IBD) like Crohn’s or colitis (men and African-Americans are at a higher risk of developing colorectal cancer. Other risk factors include diet (particularly consuming too much red meat), obesity, lack of physical activity, smoking, and alcohol use.

Here’s an overview of how well medical cannabis might work for colorectal cancer, keeping in mind that this is not medical advice and is speculation.

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Key Information

Total Studies = 28

Types of Study = Laboratory Study (18); Meta-Analysis (6); Animal Study (4)

No. of Positive Results = 26

No. of Inconclusive Results = 2

No. of Negative Results = 0

Cannabis Compounds of Interest

Cannabinoids: THC, CBD, CBG, THCA, CBDA, CBGA

Terpenes: Limonene, pinene, beta-caryophyllene, geraniol, and many others display anti-cancer properties in lab studies

Flavonoids: Quercetin, apigenin

Plus Points

• A high number of positive results from current studies.
• The endocannabinoid, anandamide, inhibited the growth of colorectal cancer cells in lab studies.
• Patients with colorectal cancer display altered endocannabinoid and ceramide levels
• In one mouse study, increased endocannabinoid levels reduced the development of precancerous lesions in the colon.
• Cannabis is full of compounds that can help with the side-effects of cancer treatment, such as chronic pain, nausea, and appetite loss.
• The colon is full of cannabinoid receptors – targeting them could help reduce inflammation associated with colorectal cancers.

Minus Points

• There are no human trials, so nothing definitive can be stated yet regarding cannabis’ efficacy for colorectal cancer.
• Caution is required when combining cannabis and immunotherapy, as cannabis may decrease efficacy.
• Little information on combining cannabis with other treatment methods

Strength of Evidence

Moderate

What is Colorectal Cancer?

Colorectal cancer (CRC) is cancer that starts in the colon or rectum. Colon cancer begins in the large intestine and is sometimes called bowel cancer, whereas rectal cancer begins in the back passage (rectum). The colon is the final part of the digestive tract.

Warning signs of colorectal cancer include weight loss, loss of appetite, blood in the stool (feces), decreased caliber (thickness) of stools, worsening constipation, nausea, and vomiting. Approximately 50% of individuals with CRC do not report any alarming symptoms. Although genetic factors play a role in CRC development, 95% of cases occur in people with little or no genetic risk.

CRC originates from the epithelial cells lining the colon or rectum of the gastrointestinal (GI) tract. There are mutations in a particular pathway called the “Wnt signaling pathway,” responsible for forming bone, heart, and muscle tissue. Mutations in the Wnt pathway are implicated in developing colorectal and breast cancer, prostate cancer, glioblastoma (brain or spinal cord cancer), and type-II diabetes.

How is Colorectal Cancer Currently Treated?

Despite colon cancer and rectal cancer being grouped due to similar symptoms and genetic makeup, they are different in many aspects. This makes a difference to the treatments offered, survival rates, and who is impacted.

Colon Cancer

• Radiation therapy is less commonly used, as the bowels are particularly sensitive to radiation.
• Surgery is usually preferred over chemotherapy for stage 1 colon cancer. Chemotherapy is more often offered during stage 3 or 4 colon cancer.
• Men and women are equally at risk of developing colon cancer.

Rectal Cancer

• Radiation therapy is more commonly recommended.
• Metastasizes more easily.
• Is more common in men.

Similarities in Colon Cancer and Rectal Cancer Treatment

• Same risk factors — diet (particularly consuming high amounts of red and processed meat), low levels of physical activity, smoking, high alcohol intake, suffering from an IBD, and genetics.
• Same symptoms – weight loss, loss of appetite, blood in the stool (feces), changes in bowel movements, nausea and vomiting.
• Incidence rates
• The genetic makeup of the two types of cancer.
• Chemotherapy is usually applied in stage 3 or stage 4 of colon and rectal cancer.
• Opioids may be prescribed to reduce cancer pain.

Medical Cannabis and Colorectal Cancer

Although there are no human trials, the literature suggests cannabis extracts and “cannabinoids have a high potential to be turned into promising drugs” for CRC.

There are no human trials on using cannabis to treat CRC, but the number of positive lab studies and meta-analyses suggests cannabis and cannabinoids have some anticancer activity. There are several theories as to why this might be the case for CRC specifically, including:

• COX-1 and COX-2 enzymes are implicated in inflammation and the development of colorectal cancer, and cannabinoids like THCA may inhibit COX-2 enzymes.
• By activating CB2 receptors, THC may reduce pro-inflammatory cytokine production and prevent colitis-associated colon cancer.
• One study looking at synthetic cannabinoids found that they may help reduce CRC cell viability but not by targeting cannabinoid receptors. The same study also looked at phytocannabinoids like THC and CBD but focused on synthetic cannabinoids as, in this instance, they were found to be more effective for CRC.
• Cannabis may help treat the side-effects of radiotherapy and chemotherapy, such as anxiety, nausea, vomiting, and pain.

Any Information on Specific Cannabinoids, Terpenes, and Flavonoids for Colorectal Cancer?

There is little information about specific cannabis compounds and what specific health problems they can be used for. To point out what some studies show when it comes to particular cannabinoids, terpenes, and flavonoids in relation to CRC:

• One study suggests that cannabigerol (CBG) “demonstrated a high capacity for tumor volume reduction.”
• One study on mice shows that THC prevented inflammation and the development of colon cancer. There are no trials on humans that replicate these findings.
• As noted above, tetrahydrocannabinolic acid (THCA) also has anti-inflammatory effects.
• One large observational study of cancer patients using cannabis over six months “demonstrated a decreased number of patients with severe pain and decreased opioid use, whereas the number of patients reporting good quality of life increased.” Cannabis and cannabinoids may be helpful in cancer pain management, but more clinical trials are needed to get a better grasp of its efficacy and control for other variables.
• In addition to the above, Dronabinol (Marinol) is a synthetic form of THC available to treat nausea and vomiting caused by chemotherapy and appetite and weight loss in patients with HIV infection.
• In lab studies, THC, THCA, CBD, CBDA, CBG, and CBGA have all inhibited cyclooxygenase (COX) enzyme activity.
• Cannabidiol (CBD) has been shown to reduce colorectal cancer cell proliferation in experimental models of colon cancer.
• Terpenoids are being explored as anticancer agents.
• The dietary terpene, lupeol, targets colorectal cancer cells, decreases viability, and induces apoptosis.
• The flavonol, quercetin, displays anticancer activity.

Dosing Medical Cannabis and Colorectal Cancer

There is no information on dosing cannabis for colorectal cancer, and some anecdotal reports suggest that suppositories could be helpful. This method of ingestion also bypasses the liver, so it is not associated with the psychoactive effect orally consumed cannabis has.

Conclusion

Although many lab results suggest that cannabis extracts have the potential to prevent the proliferation of colorectal cancer cells, there are no clinical trials that confirm these lab results. Although the data is promising, no definitive answers can be given on whether or not cannabis or specific cannabinoids can be utilized in to treat colorectal cancer. Human trials are needed to establish efficacy and dosing protocols.

Please note: the information in this article does not constitute medical advice.

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