There's insufficient to no evidence that marijuana is an effective treatment for cancer. That's what the National Academies of Sciences, Engineering, and Medicine said in a comprehensive report on the health effects of marijuana in January. But this report's conclusion might already be in question.

GW Pharmaceuticals (NASDAQ:GWPH) recently announced encouraging results from a mid-stage clinical study of a cannabis-based drug combination in treating an aggressive type of brain cancer. Could marijuana potentially become the next "miracle drug" for treating cancer?

Marijuana in test tube

Image source: Getty Images.

Promising potential

A combination of two chemicals derived from marijuana, tetrahydrocannabinol (THC) and cannabidiol (CBD), was administered to 12 patients with recurrent glioblastoma multiforme (GBM). Another 9 patients were given placebo. All patients were also on temozolomide, a standard chemotherapy used for treating brain cancer. Results from the THC/CBD patient arm of the study were significantly better than the placebo group.

The study found that patients who were treated with the THC/CBD combo had an 83% survival rate at one year compared to a 53% survival rate for patients in the placebo cohort. Median survival for the patients taking the THC/CBD combo was over 550 days. Median survival for the placebo group was 369 days.

Researchers were also encouraged by the safety profile of the cannabinoid treatment. GW Pharmaceuticals' THC/CBD combo was generally well tolerated. The most common adverse events were vomiting, dizziness, nausea, headache, and constipation.

Glioblastoma multiforme is one of the most common types of brain tumors -- and one of the most aggressive. Only 28.4% of patients on average survive one year after diagnosis, with 3.4% surviving to year five. The severity of the disease and lack of effective treatments has led to a flurry of activity by biopharmaceutical companies and cancer research organizations. Over 150 mid- and late-stage clinical trials targeting GBM are currently active.

Based on these positive results, GW Pharmaceuticals is following up with regulatory agencies on a pivotal clinical study for the THC/CBD combo in treating GBM. The company is also exploring opportunities to evaluate the cannabinoid treatment in treating other forms of cancer. 

Cannabinoids and cancer 

Cannabinoids have shown considerable potential for treating other indications (such as GW Pharmaceuticals' cannabinoid Epidiolex in treating rare forms of epilepsy). However, there hasn't been much progress thus far with the drugs tackling cancer. 

Two drugs that contain a synthetic form of THC are currently available for treating nausea associated with chemotherapy. Dronabinol and nabilone were both approved in 1985.

Cannabics Pharmaceuticals has a late-stage study underway evaluating cannabis capsules for treating cancer anorexia cachexia syndrome (CACS), a disorder where cancer patients lose skeletal muscle and fat. Another phase 2/3 study is being conducted in Mexico for nabilone in reducing anorexia and improving the quality of life in lung cancer patients.

There are also some clinical studies in progress evaluating CBD in treating graft-versus-host disease (GVHD). GVHD occurs after a bone marrow or stem cell transplant from another person and can be a complication of cancer treatments.

All of these examples, though, only address peripheral indications related to cancer. None focus on marijuana-based drugs tackling cancer head-on. That's why GW Pharmaceuticals' latest results are so important.

It's still early

Any drug that could extend the life expectancy of patients with severe brain cancer might be legitimately called a "miracle drug," especially considering the lack of effective treatments so far. However, it's too soon to bestow that description on GW Pharmaceuticals' THC/CBD combo.

The number of patients included in the mid-stage clinical study conducted by the company was small. More studies with more patients are needed. The good news is that's exactly what GW Pharmaceuticals is planning. Perhaps in the next few years, there will be plenty of evidence that marijuana-based drugs are effective in treating cancer. And it shouldn't require a miracle for that to happen.

Keith Speights has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.