Patients keep asking if they should take cannabis for their cancer. The answer is still no | Ranjana Srivastava

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It’s fair to say my patients were using cannabis long before I knew it was a “thing”.

My first memory of encountering the drug was a decade ago at the bedside of a dying patient. I was about to commence a morphine infusion when a burly man quietly asked me to step outside. Moments later, my apprehension turned to surprise when, tears streaming down his face, the son begged me to wait while his brother procured some cannabis from an underground supplier, “just in case it works”.

“Works for what?” I asked, surprised.

“As a cure for cancer,” he stammered.

My heart melting, I counselled the son that nothing would rescue his actively dying father who deserved to die with dignity. Shortly afterwards, the inevitable happened but I vividly recall the fervour with which the son believed in cannabis as a cure for cancer.

Today, cannabis is no longer a back-channel substance evoked in hushed tones. Indeed, cancer patients openly ask to access it and expect proper help. Oncologists pride themselves on handling questions about interventions proven and debunked, but when it comes to cannabis, most doctors won’t prescribe it and most hospitals don’t allow it. So the most common attitude patients encounter is “we don’t do that here”, leaving them feeling dismissed, or worse, judged.

Recently, when my elderly patient announced her intention to try cannabis for pain, I hesitated, preferring she try conventional analgesics. Nevertheless, when she insisted, I let her find her own way to an online doctor since I didn’t know how to prescribe or monitor the drug. Soon, her family reported her more confused and forgetful before she fell over, bringing the experiment to an end. I had a nagging sense of guilt that I didn’t do better by her.

Up to 40% of cancer patients report using cannabis. For a psychoactive substance that vies with caffeine, alcohol and nicotine for global popularity, to ignore cannabis is to do patients a disservice. Therefore, I was glad to see the American Society of Clinical Oncology release some evidence-based guidelines to help oncologist steer their patients.

Here are some key points.

Cannabis is associated with significant side effects

The body absorbs about 10% of oral and 30% of inhaled cannabis. The psychoactive effects of inhaled cannabis occur within seconds while oral cannabis can take up to two hours to work. Acute side effects include sedation, euphoria, dizziness, vertigo, mood changes and hallucinations. Long-term toxicity can affect the liver, heart and brain.

There are potential drug interactions, but we don’t yet have evidence-based answers about which ones. Meanwhile, every cannabis user and prescriber must be aware of these pitfalls.

It is not a cure for cancer

Cannabis is not a treatment, let alone a cure for cancer. It is not a substitute for chemotherapy and can cause significant fatigue, confusion and mood disturbances.

The advent of immunotherapy has led patients to experience unprecedented responses. Despite the anecdotal reports of cannabis demonstrating anti-inflammatory properties, researchers warn that cannabis consumption could interfere with immunotherapy. This has resulted in a recent recommendation to avoid cannabis while undergoing any form of immunotherapy.

Cannabis may slightly improve nausea and sleep

For patients who are severely nauseous despite using the many strong medications now available, oral cannabis may provide relief. However it should not be used as a first-line drug to treat nausea and vomiting or as a preventative agent during chemotherapy or radiotherapy.

In relation to sleep, cannabis is associated with a very small improvement in adults with cancer pain, but it may come at a cost of other troublesome symptoms, so caution is warranted. The bottom line is that for most patients, there are better agents to curb nausea and aid sleep.

It does not reduce pain

In four randomised controlled trials focusing on cancer pain, cannabis did not provide a significant benefit. This is why, outside of a clinical trial, guidelines do not recommend using cannabis for cancer pain relief.

The effect of cannabis on anxiety and depression is unclear

In a systematic review, no study addressed psychological symptoms in a robust way. Hence experts make no recommendation about cannabis and patients should try other means of managing the psychological sequelae of cancer.

It does not benefit appetite and weight

Loss of appetite and weight is a disturbing fact for many cancer patients. Unfortunately, cannabis does not provide a benefit in either instance and hence should not be used.

All products are not the same

Synthetic cannabis products are more powerful than natural ones and may lead to more heightened toxicities. If prescribing, doctors and patients should adopt a “start low, go slow” approach while constantly reviewing risks and benefits.

Chronic users can develop serious problems

Early cannabis use is a predictor for future dependence and chronic users are at higher risk of psychiatric illness. Long-term daily cannabis users may experience severe withdrawal symptoms including irritability, insomnia, anxiety and pain.

Cannabis users should avoid driving

A meta-analysis found that cannabis users are at significantly higher risk of being involved in car crashes. The percentage of car crashes involving cannabis and alcohol has risen sharply, turning this into a serious issue for oncologists to discuss with their patients.

There is a lot we don’t know

For a drug so ubiquitous, there are many gaps in our knowledge. Are there preparations with meaningful anticancer activity? Could some forms mitigate the feared side effects of cancer therapy? How do we spare patients stigma and financial toxicity while helping them derive benefits? Acknowledging what we don’t know is the first step to asking relevant questions in patients’ interest.

There was a time when oncologists balked at the idea of discussing cannabis, therefore leaving patients no choice but to find unscrupulous providers. But when their peak body publishes guidelines on the subject, it signals a new attitude of openness.

Cannabis isn’t going away and I am looking forward to learning more about its role, if any, in cancer. When patients ask, “Doctor, should I take cannabis for my cancer?” the answer is still no. But at least we are talking.

Ranjana Srivastava is an Australian oncologist, award-winning author and Fulbright scholar. Her latest book is called A Better Death