When people are diagnosed with cancer, their oncologist may talk to them about using cannabis as an adjunct therapy. However, it’s actually friends and family who are more likely to suggest it, as research shows that’s how most information about using cannabis medicinally is shared.
Many people living with cancer use cannabis or medicines that contain cannabinoids, its primary active compounds, to relieve side effects of cancer chemotherapy and radiation treatments, including nausea, vomiting, loss of appetite, and pain. Some even use it to directly fight cancer tumors.
The role of medicinal cannabis in the treatment of cancer is one of the best understood of all its possible uses. The evidence on this page is based primarily on two comprehensive scientific reports commissioned by the US government—the 1999 report of the Institutes of Medicine (IOM) and the 2017 report of the National Academies of Science Engineering and Medicine (NASEM). The NASEM report reflects the consensus conclusions of 16 renowned experts who systematically reviewed over 24,000 studies published since the IOM report and is considered a definitive resource on the state of the research on cannabis and the cannabinoids it contains. Both reports found that cannabis can have a role in cancer treatment as palliative care for nausea, vomiting, and pain.
Another authoritative resource is the National Cancer Institute (NCI), a division of the US National Institute of Health, which classifies cannabis as a Complementary and Alternative Medicine. Experts from this institution note that, in addition to reducing side effects of cancer treatments, medicinal cannabis can reduce anxiety and improve sleep, which may help patients fight off the disease.
The Endocannabinoid System
The search for how cannabis affects the body led to the discovery in the 1990s of the endocannabinoid system (ECS). Recent research has revealed the ECS to be a master regulator — modulating everything from metabolism and mood to sleep and immune function. For this reason, NIH researchers concluded that it that it may be a target for treating virtually all human diseases, including cancer.
The ECS plays a role in many aspects of cancer and its treatment, including the experience of nausea, vomiting and pain. The ECS also modulates immune response as cancers develop and the body attempts to fight it.
The ECS is responsible for homeostasis or balancing the body’s systems, so its level of function or “tone” influences how we experience pain, hunger, and nausea. More research is needed to fully identify the mechanisms, but evidence indicates an endocannabinoid tone is responsible for regulating nausea and vomiting. For instance, blocking cannabinoid receptors produces nausea and vomiting in humans and animals. Similarly, people who experience motion sickness have been found to have lower ECS function than those who don’t.
Pain is transmitted through the central, autonomic, and peripheral nervous systems, and cannabinoid receptors have been identified as playing a clear role in modulating pain signaling in each of those systems. Cannabinoid receptors are prominent in the part of the spinal cord that processes sensations such as pain. They are also present in peripheral areas of the body, particularly skin layers, where they modulate pain.
While there is still much to learn about the mechanisms of how cannabinoids fight tumors, scientists have described some of the ways the ECS does it. Activating cannabinoid receptors creates chemicals that induce two types of cell death in cancers of several types, including glioma, melanoma, hepatic, pancreatic, and breast cancers. The ways cannabinoid receptors help resist the spread of cancer cells and can limit the blood flow to tumors involve complex cascades of chemicals that are not yet fully understood, but their ability to do so is well established by laboratory studies with cancer cell lines and animals.
Cannabis & Chemo
Chemotherapy has significant and severe side effects. Even the thought alone of going to another round of therapy can induce nausea and vomiting in patients. It is one of the most abhorred treatments in medicine that is given. Limiting and addressing those side effects would dramatically improve the quality of life of those undergoing chemotherapy, and may even significantly improve compliance.
Nausea and Vomiting
Cannabis is one of the oldest remedies for treating nausea, and the IOM and NASEM reviews of studies conducted since the 1970s concluded that cannabis is effective for controlling nausea and vomiting. Studies have found people generally prefer cannabis-based medicines to pharmaceutical antiemetics.
That fits with the clinical trials that led the US Food and Drug Administration (FDA) to determine THC is safe and effective for treating nausea and vomiting due to chemotherapy. The FDA has approved two THC medications, dronabinol (MarinolTM/SyndrosTM) and nabilone (CesametTM), which are synthetic versions of THC, available in pill or liquid form.
While these FDA-approved medicines contain the same active ingredient as most medical marijuana products, they are not the same in practice. The FDA-approved medicines are taken by mouth, but oral medications can be impossible to keep down for someone who is vomiting uncontrollably. They also have a delay in onset, taking an hour or more to provide relief, and adjusting dosage can be difficult. Nausea as well dramatically decreases absorption as well, making it harder for medications taken orally to have an impact. By contrast, inhaled cannabis delivers the same therapeutic effects within seconds, allowing for more efficient absorption, faster relief, and improved dosage control.
Many people report that whole-plant medical products work better and with fewer side effects than the single-cannabinoid pharmaceuticals. That may be because of how the hundreds of active compounds in the plant work together therapeutically.
Pain is by far the most common qualifying condition for the more than three million Americans currently registered in-state medicinal marijuana programs. Treating pain with medicinal cannabis has been the focus of more than two dozen randomized double-blind placebo-controlled clinical trials involving thousands of participants. Those gold-standard studies have shown that medicinal cannabis is well tolerated and can offer at least moderate alleviation for most types of pain associated with cancer and its treatment, including difficult-to-treat neuropathic pain. The NASEM and NCI found conclusive or substantial evidence for the use of cannabis or cannabinoid medicines for treatment of chronic pain.
Modern investigation of medicinal cannabis in pain treatment includes laboratory experiments, animal studies, and human trials, all of which indicate it can be a safe and effective treatment. Treating pain with medicinal cannabis has been the focus of more than two dozen randomized double-blind placebo-controlled clinical trials involving thousands of participants. Those gold-standard studies have shown that medicinal cannabis is well tolerated and can alleviate most types of pain. The expert consensus of the NASEM report is that “there is substantial evidence that cannabis is an effective treatment for chronic pain in adults.”
Many of the studies with people using inhaled cannabis to treat pain were conducted by the Center for Medicinal Cannabis Research, a consortium of university research scientists. Their studies targeted neuropathic pain from various sources, including spinal injury, diabetes, and HIV. They also tested cannabis in experiments where they induced pain, which showed a dose-dependent relationship in which lower doses of THC relieved pain but higher doses produced hyperalgesia, increased sensitivity to pain. In all cases, inhaled cannabis and modest doses were effective in controlling pain.
Cannabis can also work well in combination with other analgesics. Studies show that medicinal cannabis can make opioids more effective at lower doses. A “substitution effect” in which patients reduce opioid use once medicinal cannabis is added has been identified in surveys and a study of people living with pain. A study of opioid prescribing patterns in the US found significant reductions in the number of prescriptions written after states launch medicinal cannabis programs.
As more people living with cancer have turned to cannabis as a treatment, anecdotal reports have accumulated of success with reducing tumors and even achieving remission. These reports are consistent with the several hundred laboratory studies with animal models of cancer and human cancer cell lines. The National Cancer Institute lists information on some of these preclinical studies that demonstrate the anti-tumor properties of cannabinoids.
Scientists have identified several ways that cannabinoids act selectively on cancer cells, including shutting off the blood supply to tumors, preventing the spread of cancer cells, and reprogramming cancer cells to die off. Cannabinoids have been shown to be effective fighting many types of cancer, including those of the brain, skin, blood, breast, colon, liver, and lung.
Only a few human trials have attempted to use medicinal cannabis to directly fight cancer tumors, but results have been promising and align with anecdotal reports and the many preclinical studies. Many people who use cannabis to fight cancer take relatively high doses of THC as oral extracts, as much as 1,000mg/day, about 100-times a standard 10mg dose. Ramping up to a dose in that range can be challenging, as higher doses are more likely to produce psychoactive effects that can be unpleasant. With experience, many people learn how to compensate for those effects. As with other therapeutic effects, studies indicate that THC and CBD in combination have more success fighting tumors.
As effective as cannabinoids appear to be in selectively killing tumor cells, they may also act to protect healthy cells. Scientists speculate that the anti-inflammatory and anti-proliferation effects of cannabinoids may help protect against several types of cancer.
Since the late 1990s, the medicinal use of cannabis has expanded dramatically, and now 47 states and more than 30 countries allow cannabis in one form or another to be used in the treatment for some conditions. Often, laws define the types of conditions that qualify an individual to obtain, possess and use cannabis or cannabis products. Cancer is explicitly listed as a qualifying condition in almost all states and some countries such as Italy, but even in places where it’s not, people living with cancer can qualify for access on the basis of symptoms associated with cancer and its treatment, such as chronic pain, nausea, or the loss of appetite and wasting known as cachexia. Most countries that allow use of medicinal cannabis leave the decision to physicians. Prescription cannabinoids such as dronabinol (THC) and EpidiolexTM (CBD) are available throughout the US, and dronabinol is an approved medication in Canada, Australia, Germany, and New Zealand.
US States that Specify Cancer as a Qualifying Condition
Alaska, Arkansas, Arizona, California, Colorado, Connecticut, Delaware, District of Columbia, Florida, Georgia, Hawaii, Illinois, Iowa, Louisiana, Massachusetts, Michigan, Missouri, Minnesota, Montana, New Jersey, New Hampshire, New Mexico, Nevada, New York, North Dakota, Ohio, Oregon, Pennsylvania, Rhode Island, South Carolina, Utah, Vermont, Washington, and West Virginia
Maryland specifies pain, nausea, wasting, and anorexia – all potential symptoms of cancer or its treatment. Maine, Oklahoma, and Virginia allow recommendations for any debilitating condition a physician deems appropriate.
US states that allow some form of medicinal cannabis use but exclude persons living with cancer are: Alabama, Kentucky, Mississippi, North Carolina, Tennessee, Texas, Wisconsin, and Wyoming.
The three US states with no legal access to any cannabis product are: Idaho, South Dakota, and Kansas
Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body, ultimately leading to death. Over 100 types of cancer affect humans and 14 million people are diagnosed with it each year. The most common types of cancer are lung cancer and prostate cancer in men, and breast cancer, lung cancer, and colorectal cancer in women. It is one of the leading causes of death worldwide.
Some of the causes of cancer are preventable. One out of five deaths caused by cancer is related to tobacco use. Another 10% is due to obesity, lack of physical activity, or excessive drinking of alcohol. Other cases are related to infections (especially in the developing world), as well as environmental pollution and exposure to ionizing radiation. The risk of cancer increases significantly with age. We also know that diet affects our risk of developing cancer.
Most cancers are initially recognized either because of the appearance of signs or symptoms or through screening. People with suspected cancer are investigated with medical testing which include physical exams, blood tests, imaging, and biopsies.
Cancer can sometimes be prevented with a healthy lifestyle, primarily a balanced diet and exercise, and avoiding known risk factors such as smoking. These can also improve the chances of survival. Some vaccines, such as those that prevent human papillomavirus or hepatitis B, decrease or prevent infections which can lead to cancer. There are even reports that the healing process of cancer can be aided by staying positive, alternative medicine, and meditation.
One method of treating cancer is chemotherapy, often shortened to “chemo.” The treatment aims to eliminate cancer from our bodies. Chemotherapy prevents many cells from reproducing in an uncontrolled manner. Cancer cells tend to reproduce more than normal cells in our body, so chemotherapy often targets them first, though many normal cells fall victim to the treatment as well.
Reasons to do chemotherapy
- Shrinking a tumor before radiation therapy or surgery — also called neo-adjuvant chemotherapy
- Destroying remaining cancer cells following surgery or radiation therapy — also called adjuvant chemotherapy
- Eliminating returning cancer cells or preventing them from spreading to other parts of the body
- Enhancing the effect of other therapies — biological or radiation.
In general, there are four types of chemotherapeutic drugs:
- Alkylating agents kill the cells at different stages of their life cycle
- Antimetabolites mimic proteins that the cells need to survive but offer no benefit, so the cells which consume them starve to death
- Plant alkaloids prevent the cells from growing and dividing themselves
- Anti-tumor antibiotics, as their name suggests, prevent the cells from reproducing
The drugs can be delivered either directly into the bloodstream to spread throughout the body or can be targeted to the specific areas in which the cancer is present. Surgery and radiation therapies, on the other hand, target specific areas.
Chemotherapy doses may be based on a person’s body weight and differ for children and adults. To ensure safety even further, chemotherapy is often administered in cycles. This is to mitigate adverse reactions, which are often inevitable with chemotherapy. Recovery time periods between cycles allow normal cells to recover and the body to recuperate.
Chemotherapy agents often damage the cells of the heart, kidneys, bladder, lungs, and nervous system, and there are medications that can be taken with the chemo to help protect the body’s normal cells. However, the normal cells most likely to be damaged by chemo are blood-forming cells in the bone marrow, hair follicles, and cells in the mouth, digestive tract, and reproductive system.
Chemo Side Effects
Chemo is an aggressive treatment. As a process that eliminates cells within the body, chemotherapy is no stranger to side effects. However, the severity of the side effects depends on medical condition, gender, age, and risk of infection during the process. Common symptoms include:
- Nausea and vomiting — these affect over 70% of patients. In order to help manage these side effects, antiemetic drugs are often given, as well as ginger or ginger supplements.
- Hair loss — after a few weeks of treatment, hair might fall out or thin on different parts of the body. Some people may choose to wear wigs to hide their hair loss.
- Fatigue—this might be present during the entire process or just following certain activities. Most chemotherapies will cause fatigue to a certain degree in practically all individuals. Also, patients should notify doctors of their symptoms as this may indicate another potentially dangerous adverse reaction, such as anemia.
- Hearing impairment — chemotherapy can lead to temporary or permanent hearing loss in some patients.
- Low white blood cell count — White blood cells make up the major component of the body’s immune system and ability to fight infections. Chemotherapy often destroys these cells and leaves our bodies prone to infections our immune system normally fight. Antibiotics can help in minimizing that risk, as well as maintaining personal hygiene and avoiding others with active infections.
- Low blood platelet count and bleeding problems — this can lead to blood clotting problems or bleeding. Platelets are responsible for stopping bleeds when we have them. Without platelets, we can bleed indefinitely. If the count drops below a certain threshold, a blood transfusion may be administered.
- Low red blood cell count and anemia — low red blood cell levels indicate that less oxygen is being carried to all the tissues in the body. Anemia can cause constant tiredness and shortness of breath. If the anemia is severe, an urgent blood transfusion may be needed. Erythropoietin, a drug that stimulates the production of red blood cells, can be prescribed. Eating sources of iron, such as green leafy vegetables, beans, meat, and nuts can minimize the risk of anemia.
- Mucositis — the inflammation of the mucous membrane can affect any part of the digestive system, including the mouth, stomach, and intestines. Symptoms begin after seven to 10 days of treatment and might manifest themselves as pain in the mouth. Ulcers can then appear on the lining of the mouth and eating can be painful and extremely uncomfortable.
- Loss of appetite — this could be a result of either chemotherapy or cancer itself. Cancer sufferers can lose a significant amount of weight, muscle mass and become very thin, lacking basic nutrients. In extreme cases, in which the patient is unable to eat independently, a feeding tube is usually administered in a hospital.
- Pregnancy and fertility — libido is mostly absent during chemotherapy. At the same time, fertility in both genders could be reduced depending on the treatment program. It usually returns when the treatment is over. However, if you’re considering having children in the future, look into the option of freezing your sperm or embryos. Chemotherapy is usually avoided if possible during pregnancy, to avoid causing dangerous adverse reactions for the fetus.
- Bowel problems — diarrhea and constipation are common in the first few days after treatment, as the body expels the damaged cells from the body. Sometimes they can continue throughout the chemotherapy treatment.
- Cognitive and mental health problems — three out of four patients report problems with thinking and short-term memory during treatment. Some report it for even months or years after the chemotherapy is over. Depression may follow, though it may be caused both by dealing with cancer and the treatment itself.
Chemotherapy may also have a different effect depending on your gender. The treatment may cause menstruation to stop (menopause) among women, which leads to hot flashes and dry skin. Under the age of 40, it might weaken the bones in the long term and cause osteoporosis. Chemotherapy also may lower sperm count, which can end in temporary or permanent infertility.
An estimated two out of three childhood cancer survivors experience some additional late side effects, such as heart problems and an increased risk of a heart attack. They might also have liver problems, kidney problems, blood vessel problems (including an increased risk of stroke), and lung problems. Chemotherapy can also slow bone growth. Other possible future problems are cataracts, obesity, infertility, memory problems, and the loss of hearing and vision.
Some people experience rare side effects. These include changes in the color of the skin, swelling on the hands and feet, personality changes (including aggressiveness), and permanent nerve damage, which might manifest as intense chills or tingling.
While the list of possible side effects might seem very long, some patients may not experience most or even any side effects at all. Others usually notice the side effects during the first few weeks of treatment and report they get more intense over each treatment cycle. Before the beginning of your treatment, consult your doctor on side effects to watch out for and how to prevent or manage them.
Since cancer in general and even the side effects of chemotherapy may affect your mood, it may also be prudent to get mental health support as well. This can be a therapist, psychologist, or even a cancer support group. Patients often benefit tremendously from mental health support, even if it is preventive.
Some clinics offer alternative and complementary treatments in addition to conventional medical therapies. These have been proven safe and effective in scientific studies and may offer help in managing side effects and improving quality of life.
Common complementary therapies include meditation, relaxation, and massage. For reducing chemo-related nausea and fatigue, many patients try acupuncture. Note that some treatments could interfere with the effects of chemotherapy or make side effects worse, so consult with your doctor before trying them out.
Tips for managing fatigue
Chemotherapy can cause anemia or make you generally exhausted and sometimes depressed. Ways of dealing with this include therapy, relaxation techniques, exercise, support from friends and family, organized support groups and sometimes pharmacotherapy. In some cancers, exercise alone can help improve survival rates, and even prevent cancer from recurring, or coming back.
It is okay to ask for and accept help. Use friends and family to assist with shopping, driving, and general housework. Share the impact of the treatment with your workplace. Some employers may allow you to work flexible hours or remotely during or after the treatment. Some may even allow you to take time off until the treatment is over.
Tips for coping with nausea and decreased appetite
Consult your doctor and perhaps a nutritionist for strategies on diet before, during, and after receiving chemotherapy.
It is common during chemotherapy to experience diarrhea and constipation. To help avoid this, eat freshly cooked foods. Avoid raw fish, meat, and eggs and wash fruits and vegetables well before eating them. Foods rich in fiber can be helpful, such as wholegrain bread and pasta. If solid foods are causing you too much trouble in digesting, try enriched drinks with powdered milk, yogurt, or soy.
Loosen the bowels by drinking plenty of fluids, both warm and cold. Limit fluids that stimulate the bowel, such as alcohol, fruit juice, soft drinks, and tea or coffee. Also, avoid foods that can aggravate mouth sores, like spicy and acidic foods, and quit smoking.
for your help