Medical marijuana and the treatment of breast cancer

While the survival rate for breast cancer is relatively high, treatment is far from foolproof, which is why researchers are constantly on the lookout for new alternatives to surgery, medications, and/or chemo/radiotherapy. Well, research suggests cannabis may just offer this alternative. So the big question is if cannabis can really kill breast tumors?

The American Cancer Society estimates that over 250,000 new cases of invasive breast cancer will be diagnosed in US women in 2017. It also estimates roughly 40,000 American women alone will lose their battle with breast cancer this year.

Like other types of cancer, breast cancer can affect women of all ages, races, and socioeconomic backgrounds. While breast tumours are obviously more common in women, they can even affect men in some cases.


Breast cancer is defined by the abnormal growth of cells in the breast. More precisely, the most common types of breast cancers tend to form in the ducts that carry milk to the nipple or in the glands that produce breast milk (known as ductal and lobular cancers, respectively).

Breast cancer is the second most common cancer in women. Death rates for breast cancer have dropped significantly, especially between the 1980s and early 2000s. This is possibly due to better treatments and earlier diagnosis.

As breast cancer cells grow they usually form a tumor, which is generally detected via x-ray or by feeling a lump in the breast. Malignant tumors will grow rapidly, spreading into surrounding areas and distant parts of the body. Benign tumors, on the other hand, will not spread outside of the breast and usually are not harmful.

Breast cancer cells can spread to other areas of the body via the blood or the lymph system. If cancer cells manage to spread to the lymph nodes close to the chest they may also manage to reach other nodes throughout the body and possibly even affect other organs.

The treatment for breast cancer varies depending on the specific kind of tumor, the stage of the cancer, and the age of the patient. However, breast cancer is most commonly treated using surgery to remove the cancer tissue. This may then be followed with chemo or radiation therapy.

Standard surgeries used to treat breast cancer include:

  • Mastectomy: Removal of the whole breast
  • Quadrantectomy: Removal of one-quarter of the breast
  • Lumpectomy: Removal of a small part of the breast

Following surgery, some patients may wish to undergo breast reconstruction surgery so as to repair and aesthetically improve the treated site. While it is not common, breast cancer can also affect males.


Cannabis is receiving a growing amount of attention from oncologists, researchers, and cancer patients. When talked about in relation to cancer, cannabis is often mentioned as a solution to managing side effects from treatment and/or medication, such as nausea, vomiting, or pain. However, some evidence also suggests cannabinoids may help treat and manage the actual growth of a tumour.

One study, published in the journal of Molecular Cancer Therapeutics in 2011, found cannabidiol (CBD) may actually help kill cancer cells. The in vitro study found that CBD inhibited the survival of estrogen receptors in the breast. This ultimately lead to the death of tumour cells, while having little effect on other healthy cells in breast tissue. The research was conducted by researchers at the Beth Israel Deaconess Medical Center in Boston, USA.

Another study, published in the journal of Breast Cancer Research And Treatment by researchers from the California Pacific Medical Center, San Francisco, found similarly promising results.

The animal-based study also found that CBD was able to hinder the growth of tumors. Moreover, the study found that CBD also helped reduce primary tumor mass while simultaneously hindering the metastasis (or spread) of tumours.

One final breast cancer-specific study, published in the Molecular Cancer journal in 2010, showed that THC, the main psychoactive compound in marijuana, may also have certain antitumor effects. The study found that around 91% of ErbB2-positive breast cancers express CB2 receptors. By interacting with these receptors, both THC and JWH-133 (a synthetic, non-psychoactive cannabinoid) were able to reduce tumor growth and the number of tumors.

Some of the leading researchers into the relationship between cannabis and cancer are Guillermo Velasco and Manuel Guzman, professors at Complutense University in Madrid, Spain. Both Guzman and Velasco have argued that cannabinoids may help kill cancer cells in a number of papers.

One way compounds like THC may interfere with the growth of cancers, for example, is by causing apoptosis (natural cell death). Alternatively, cannabinoids like THC may also help starve tumours by interfering with their ability to grow blood vessels. Once they get to a certain size, tumors generally need to create their own blood vessels in order to get oxygen and nutrients to the tumor site as well as remove waste material.

These findings come from studies on other types of cancers (mainly brain tumors). However, they still add to a growing body of evidence that at least shows some promise for the future of treating various types of cancer with cannabis.


Besides showing surprising antitumor effects, cannabinoids are generally used for the treatment of side effects of cancer medications and treatment. These generally include:

  • Pain
  • Nausea
  • Vomiting


While the evidence we mentioned above is certainly compelling, it is far from enough to confirm whether cannabinoids like THC and CBD can actually help control breast cancer. Nonetheless, the growing body of research into the field is producing interesting results, which (hopefully) will evoke further clinical trials in the future.

Note: We have taken the utmost care and precaution whilst writing this article. That being said, please take note of the fact that we are not medical professionals of any kind. is strictly a news and information website. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment.