Finding the cure for cancer is the holy grail of scientific research.
As one of the leading causes of death worldwide, a cure would spare millions of people from sickness and suffering every year.
However, despite the best efforts of the world’s best scientists, the cure for cancer remains a work in progress.
Medicinal cannabis is by no means a cure for cancer, but it’s showing some potential as a treatment or co-treatment option.
In Part 1 of our series on Cannabis and Cancer, we looked at the potential of cannabis as a treatment for cancer symptoms, such as pain, nausea, and appetite loss.
Evidence for using medicinal cannabis in palliative care for cancer patients is well established.
In this article, we look at the research into cannabis as a treatment or co-treatment for cancer.
While the research is far from conclusive, there is evidence to suggest that cannabis may have anti-tumour effects in cancer patients.
As science continues to make progress in this space, medicinal cannabis may prove to be a viable treatment or adjunct therapy for a variety of cancers.
The antitumor potential of medicinal cannabis
Research to date has focussed on the potential of cannabis to inhibit or decrease tumour growth.
Since the late 1990s, there’s been a large amount of evidence demonstrating that cannabis has antitumour effects in human cells in the laboratory and genetically-engineered mice.
A 2013 review of 35 studies found that treating gliomas (a type of tumour that starts in the glial cells of the brain or the spine) with cannabis-based medicines resulted in “statistically significant reductions of the tumours’ volumes when compared to controls”.
While those studies indicate the cannabinoids are promising compounds for the treatment of cancer, they’re not particularly meaningful for humans.
Clinical trials with human patients are needed to better understand the efficacy of cannabis as an anticancer drug.
The first clinical study
The results of the first clinical study looking at antitumour effects of cannabis on cancer in humans were published in 2006.
The pilot study assessed the effects of THC on tumour cell proliferation (rapid multiplication) in nine patients with glioblastoma, an aggressive form of cancer that occurs in the brain and spinal cord.
All patients had been unsuccessful with standard therapies (surgery and radiotherapy) and had clear evidence of tumour progression.
Patients underwent surgery so that a THC solution could be administered directly into the tumour.
The study found that THC inhibited tumour-cell proliferation in humans. It also concluded that THC was safe and adverse effects were within the range of those accepted for other conditions.
Although no statistically relevant conclusions could be inferred from such a small cohort, the findings warrant further investigation.
An adjunct therapy
A randomized, double-blind, placebo-controlled, phase II study, published in 2021, found that nabiximols (1:1 ratio of THC:CBD) could be effective as an adjunct to chemotherapy.
The study of 21 patients with recurrent glioblastoma found that the one-year survival rate was 83% with nabiximols compared with 56% with placebo.
This suggests that cannabis may be beneficial to cancer patients going through chemotherapy.
However, due to the small sample size of the study, the results should be interpreted with caution.
‘A new potent anticancer drug’
An organic compound synthesised from CBD, called HU-331, has been described as “anticarcinogenic” and a potential “new potent anticancer drug”.
HU-331 is a cannabinoid quinone, which is an organic compound derived from aromatic compounds through a specific conversion process.
It’s quite complex, but quinones have been used in chemotherapy for many years.
HU-331 has shown “significantly high efficacy against human cancer cell lines” both in laboratory experiments and genetically-modified mice.
HU-331 seems to specifically inhibit an enzyme (topoisomerase II) which is important for DNA replication, repair and transcription.
Topoisomerase II is the target of several important classes of anticancer drugs.
Clinical trials are needed to determine the true potential of HU-331 as an anticancer drug.
A glimmer of possibility
The research into medicinal cannabis as a treatment for cancer has a long way to go.
Despite compelling preclinical studies and a wealth of clinical evidence for medicinal cannabis as a treatment for cancer symptoms, there is a lack of data supporting cannabis-based medicine as an effective antitumour therapy.
There is no research so far to suggest cannabis is the “cure for cancer” we’ve all been waiting for.
Most of the research so far has focussed on a specific type of cancer, glioblastoma.
There is an urgent need for more robust clinical trials looking at different types of cancers and a wider range of cannabis-based medicines.
For now, medicinal cannabis is well-established as a potential treatment for common cancer symptoms and side effects.
Patients should feel comfortable talking with their doctor about using medicinal cannabis for palliative care.
Time will tell if cannabis emerges as an effective anticancer drug.