A/Prof Peter Grimison

Australia’s strict regulatory regime for medicinal cannabis has set the scene for research exploring the benefits of cannabis preparations in cancer treatment.

Associate Professor Peter Grimison, an oncologist at Chris O’Brien Lifehouse in Sydney, says Australia has become a centre of activity in clinical trials exploring the safety and efficacy of medicinal cannabis which could help establish a better evidence base.

“I think Australia, followed by Israel, is doing the most work in cannabis,” he told the limbic, after presenting an overview of Australia-based trials on cannabis at last week’s COSA scientific meeting.

“There’s lots of interest among consumers and cancer patients in using cannabis for cancer pain, to prevent neuropathy and for other pain, but there’s very little information,” he said, noting that in jurisdictions such as America and Canada, where access to medicinal cannabis is relatively easy, “not much research is being done”.

“I think doing more randomised trials is really important to show where it is effective and safe, but also to show situations where cannabis is not effective and safe. Cannabis is quite toxic; it causes side-effects.

“Australia, because of the very medicalised regulation around cannabis, is in a very good position to be involved in that research,” he added.

Cannabis and CINV

Associate Professor Grimison is leading a NSW Health-sponsored trial on the effectiveness of medicinal cannabis in helping cancer patients who suffer from significant chemotherapy-induced nausea and vomiting (CINV).

In the randomised trial, patients took capsules containing cannabis or a placebo in addition to regular anti-nausea medications over five days before and during a chemotherapy cycle. The cannabis capsule was specially designed for the trial, with a 1:1 ratio of THC to CBD, and patients were able to increase or reduce their dose.

Preliminary results from the first 80 patients (out of 250 enrolled) have shown a small benefit, with an additional one in 10 people having good control of CINV from taking cannabis, but some having unwanted reactions.

“The take-home message is that if you take cannabis rather than a placebo, an additional one in 10 people have good control of nausea and vomiting, and one-third of people have troublesome side-effects from cannabis.  The common side-effects are sedation, dizziness, and disorientation,” the oncology specialist and educator said.

“Despite the small extra benefit and despite one-third having troublesome side-effects, well over four in five people –  or 83% – preferred cannabis to placebo,” he said.

“That’s probably because their nausea had better control but also because cannabis had some extra benefits; it helps to reduce anxiety, gives a pleasant high, stimulates their appetite and so on.”

When the trial began in 2016, no locally manufactured medical-grade product was available in Australia. The capsules were procured from Canadian supplier Tilray.  Recruitment was also a challenge, despite the trial being run by the University of Sydney with the participation of a number of NSW cancer centres.

The biggest reason for reluctance was that patients didn’t want to be restricted from driving; while others were deterred by the stigma of cannabis.  And it may be that some doctors didn’t feel it was appropriate to recruit patients for a trial of cannabis, Associate Professor Grimison said.

“I think this is important in terms of how often it’s going to be applied; there are a lot of people who don’t seem to want to have it,” he said.

“The other message is that many patients these days in chemotherapy have good control of nausea and vomiting, so we’re not recommending it for everyone. But people who do not have good control with standard medication should consider it.

“We aim to complete the trial and have some definitive results that could allow the drug to be registered.”

Associate Professor Grimison reported on findings from other Australian-based investigations of the use of cannabis in patients with brain tumours, implications for road safety, and the need to investigate possible detrimental effects for patients undergoing immunotherapy.

Cannabis and impairment

A study of driving safety for patients taking cannabis is under way by researchers from the University of Sydney’s Lambert initiative for Cannabinoid Therapy, based on a randomised trial of young people in the Netherlands and a systematic review.

They found CBD did not impair road driving, but THC or THC with CBD led to a significant driving impairment which lasted on average for four hours after ingestion of cannabis.

“The general recommendation based on this information is that people should wait at least five hours after inhaling cannabis before doing safety-sensitive tasks such as driving,” Associate Professor Grimison said.

He noted that the study involved inhaled cannabis, and the effects of an oral preparation such as cannabis oil might last longer and require more caution.  Conversely, studies have not looked at whether regular cannabis users may experience less impairment.

More work is also needed to explore the effect of cannabis on the immune system and the implications for immunotherapy, he said.

Data out of Israel showed people undergoing immunotherapy for cancer had inferior outcomes if they were taking cannabis at the same time.

A study had suggested that people lived for a shorter period; they lived for six months rather than 28 months and their cancer was more likely to progress, if they had taken cannabis.

But the study was subject to a number of biases in that the participants taking cannabis tended to be more sick, they had more aggressive tumours, they were having less effective treatment,

“But I think the take-home message is that people taking cannabis could be warned that it could make immunotherapy less effective.  The most sensible thing would be not to take both at the same time.”

Among ongoing projects, NSW Health is funding research on the use of cannabis in patients with advanced cancer, with clinicians looking at the effect on symptoms such as pain, nausea and loss of appetite of different medicinal cannabis products.

Meanwhile, a preliminary study led by Sydney-based neurosurgeon Dr Charlie Teo has been testing the tolerability of medicinal cannabis in patients with brain tumours, specifically high-grade  gliomas.

“Ultimately, the hope is that cannabis could have some anti-tumour effect for people with brain tumours, but also it could help with symptoms such as agitation and nausea and so on,” Associate Professor Grimison said.

The preliminary randomised trial found that a cannabis product with a 1:1 ratio of THC to CBD was better tolerated than a high-dose 4:1 ratio, and that it seemed to help with symptoms such as sleep disturbance.

Based on the preliminary work, the researchers propose to do a randomised trial giving half the group the 1:1 cannabis dose and half getting a placebo, to look at the long-term effect on symptoms and on brain tumour control.