Even as an increasing number of states approve the use of medical marijuana, a review of medical literature and existing data finds that huge questions remain about its true benefits and risks for patients with cancer.1
Investigators found that despite centuries of medical and recreational use, and its potential benefits as an antiemetic, as a palliative for refractory cancer pain, and as an antitumor agent, “much of the data are based on animal data, small trials, or are outdated.”
The authors of the review, which was published in JAMA Oncology, looked at the history and legal status of marijuana use, its mechanism of action, and past studies of its antiemetic effects with chemotherapy-induced nausea and vomiting, in alleviating cancer-associated pain, and as an antitumor agent.
The review's corresponding author, Tina Rizack, MD, with the Program in Women's Oncology, Women and Infants' Hospital, Alpert Medical School of Brown University in Providence, RI, told Cancer Therapy Advisor that the goal was to provide “a resource for oncologists to look at to answer their patients' questions.”
A broader review and meta-analysis looked at randomized trials examining effects on nausea and vomiting caused by chemotherapy, appetite stimulation in HIV/AIDS cases, chronic pain, spasticity due to multiple sclerosis or paraplegia, depression, anxiety disorder, sleep disorder, psychosis, glaucoma, or Tourette syndrome.2
It included a total of 79 trials involving 6462 participants. While most trials “showed improvement in symptoms,” the review concluded, they “did not reach statistical significance in all trials.”
It found “moderate-quality evidence to support the use of cannabinoids for the treatment of chronic pain and spasticity,” but only “low-quality evidence” supporting its use for the other indications, including its use for chemotherapy-associated nausea and vomiting.
An accompanying editorial questioned whether the rush to decriminalize marijuana for medicinal use was putting getting ahead of itself and urged additional research.3
“It has been argued that the lack of high-quality evidence reflects the difficulty in conducting marijuana research in the United States,” the authors wrote. “If so, the federal and state governments should support and encourage such research so that high-quality evidence can be generated to guide decisions about medical marijuana use for the conditions for which the existing evidence is either insufficient or of poor quality.”
The newer review aimed to focus specifically on the research into the benefits and risks of marijuana for cancer patients.
“In oncology we have a lot more patients asking for it both for treatment and for symptoms and there just wasn't a lot out there,” Rizack said. “There wasn't 1 summary just for oncology patients, looking at their specific issues.”
They found that even though 23 states and the District of Columbia have laws legalizing marijuana use in some form, and access to medical marijuana is increasing, “there just isn't a lot of research,” she said.
Among the challenges for researchers, she said, is the nature of marijuana itself.
Generally in clinical trials, she said, “When we compare drugs to other drugs, or to a placebo, that's something in a known quantity with a known effect. Medical marijuana is something that when it's used it's not always a controlled dosage. It's not always the same kind of plant. It's hard to do a controlled study because there are so many confounders.”
One outcome of the review she said she hopes for is that it will call attention to the lack of hard data and “maybe stimulate a little more research.”
“I think there may definitely be a role in patients who have refractory nausea and for patients that are in pain, and that there is a potential role for use as a therapeutic use for cancer treatment,” she said, “but that might be down the pipeline a few years. I think we definitely need more information.”
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