Discussing Association of Medical Cannabis, Prescription Opioid Use Among Patients With Cancer

Insights From the 2022 ASCO Quality Care Symposium 

Safiya Karim, MD MSc FRCPC, clinical associate professor, medical oncologist, Tom Baker Cancer Centre, University of Calgary, spoke with First Report Managed Care about her research, “The association between medical cannabis and prescription opioid medication use in patients with early-stage cancer: A population-based study,” which was presented at the 2022 ASCO Quality Care Symposium.

Dr Karim’s background is primarily as a health services researcher, using administrative data to look at patterns of care, quality of care and access to care, specifically in oncology.

What existing data led you and your coinvestigators to conduct this research?

A few years ago, when I first joined the department, there was an article in Journal of Clinical Oncology, looking at, I believe, patients with head and neck cancers who had curative intent surgeries or underwent chemotherapy and radiation. The study looked at the number of those patients who continued opioids for a long period after their surgery or after their chemo and radiation.

The article suggested there are a significant number of cancer patients who may continue opioids, beyond a timeline that may be reasonable, especially for someone who has gone through curative intent surgery.

In addition, a couple of years ago, we looked at medical cannabis consumption in our population of cancer patients, and found that patients who were younger, who underwent surgery and chemo and radiation, and who were at higher stages of disease, were more likely to use medical cannabis. Although we did not know the indication for their use; a lot of patients do ask about or use medical cannabis to treat pain.

So, we thought we would combine those two research themes and see what was happening in our patients in Alberta, who had been prescribed medical cannabis—looking at those early-stage patients, and asking what is the impact on opioid use in that population?

Previous studies, not necessarily specific to cancer, but in other diseases or in general states in which cannabis has been legalized, have suggested that patients might use less opioids if they're using cannabis. So, it might be a replacement.

With the current opioid epidemic, this might be a useful thing to have patients take, as perhaps cannabis is less dangerous than opioids.

On the other hand, there has been some research that suggests people who are using cannabis actually use more opioids. This is because of the synergistic effect on the opioid receptors or in the cannabinoid receptors in the brain, that suggests that those things might be synergistic.

That is basically what led us to asking the question and combining the cannabis data with our opioid data.

Thank you. You started to talk about your study and your analysis, but can you please briefly describe your study and its findings? Were any of the outcomes surprising?

In our study, we looked at patients who had early-stage cancers. We looked through our cancer registry and identified a subset of those patients who had been prescribed medical cannabis.

We then looked at the outcome of either cessation of opioid use or reduction of opioid use, at a given time after their diagnosis or after when they might've started their cannabis.

Something interesting that we observed is that patients who were prescribed medical cannabis had higher baseline usage of opioids.

In terms of their total morphine equivalents at baseline, it was higher than those who were not prescribed medical cannabis. And patients who were on medical cannabis were less likely to get off opioids, at 0 to 12 months after diagnosis or were less likely to reduce their opioid use, compared to those patients who were not prescribed medical cannabis. That was a little bit surprising to us.

We were not sure which way the data was going to go, but I think our initial hypothesis was patients might be able to get to discontinue opioids quicker if they were using cannabis.

We did not find that. We actually found that, probably people are using it more as a synergistic effect.

How can physicians use this information?

In terms of patients who might be at risk for long-term opioid use after curative intent treatment for cancer, we probably need to look at those subsets of patients who might be on cannabis as well.

Those patients might be at risk for long-term use of opioids or opioid misuse. Those are probably the patients in which we need to develop specific strategies, in which to potentially help them get off opioids at some point in time.

Do you and your coinvestigators intend to expand upon this research?

Yes, absolutely. We have a Canadian Institute of Health Research grant that is being used to further explore this question, which has different components to it, including interviewing patients with early-stage cancers and their use of opioids, as well as physicians, including oncologists, on prescribing opioids in those patients with early-stage cancer. Who is renewing their prescriptions? Who is prescribing and for how long?

That will give us a better sense of the whole picture in opioid prescribing in this population. We will try and work in our cannabis work as well, in terms of those patients that might be at highest risk for continuing long-term opioid use.

Is there anything that I haven't asked you about or anything pertaining to your research that you'd like to add?

I would say that one of the limitations, obviously, is that we only looked at people who are on medical cannabis or those who were prescribed cannabis.

In Canada, as you may know, cannabis is now legalized. There are probably many more patients who use cannabis or who experiment with cannabis, who we might not have captured in our study.

Updating the study, now that cannabis is legal, will be important. But at the same time, it might be harder to capture that data, as we had real data on patients who are prescribed medical cannabis. Our college in Alberta captures that data.

Whereas when it's legalized, we don't have the information necessarily, on how much patients are taking and for how long. But it will be an important consideration going forward.