Many Doctors Are Recommending Cannabis for Cancer Despite Inconclusive Research

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While a majority of doctors (80 percent) discussed marijuana with their patients, nearly half of them (46 percent) recommended it for cancer-related problems. But no rigorous studies in cancer patients exist.

Tennessee has become the second state to pass a law allowing pharmaceutical companies to market their products for off-label uses; a House panel advanced legislation that would expand access to private sector care outside of the Veterans Affairs (VA) health system; and almost half of oncologists recommend medical marijuana to their patients.

Having expertise in medicine means "knowing what you know, as well as what you don't know", said Andrew Epstein, MD, of Weill Cornell Medicine in New York City, who was not involved with the study.

Currently, there are 30 states with medical marijuana laws on the books, and nearly all name cancer as a qualifying condition for its use, Braun said.

The best review of medical marijuana's usefulness, released in 2017 by the National Academy of Sciences, found very mixed evidence when it comes to cancer treatment, Braun said.

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Better medical education surrounding marijuana "would help with the knowledge base of these things, so oncologists could become even more knowledgeable participants in helping guide patients and families", Epstein said.

Most cancer doctors say they don't know enough about medical marijuana to provide an informed opinion to patients. On the other hand, "healing cannabis" describes nonpharmaceutical cannabis products utilized with "medicinal intent", no matter compliance with the law. The items might be "smoked, vaporized, consumed, taken sublingually, or used topically". A significant proportion of medical marijuana products are whole-plant marijuana, which contains hundreds of active ingredients with complicated synergistic and inhibitory interactions. "So, often oncologists are borrowing from clinical trials for other diseases, or extrapolating from evidence on pharmaceutical-grade cannabinoids". Observational research studies showed that medical marijuana legalization is connected with reductions in opioid-related hospitalizations, however no randomized trials have actually compared the two methods for pain relief.

Previous surveys of oncologist attitudes about medical marijuana addressed only use as an antiemetic and were conducted prior to passage of current laws. "The scientific evidence base supporting use of medical marijuana in oncology remains thin", Braun said.

The survey included concerns about medical conversations of marijuana, views on relative efficacy versus other therapies, risks of medical marijuana versus other treatments, and items to allow comparisons of respondent qualities and their responses.

Size of practice: Oncologists who saw the most patients each week were more likely to have discussed medical marijuana than those who saw the least patients (89 percent vs. 70 percent). Majority of the respondents viewed medical marijuana as helpful in managing pain and more effective in treating anorexia and cachexia, a cancer-related adverse event characterized by muscle weakness and sudden loss of weight. When evaluating its effectiveness for other conditions, however, many oncologists responded, "I do not know", from 29 percent for nausea and vomiting to 45 percent for poor sleep. Jerry Mitchell, a medical oncologist at the Zangmeister Cancer Center in OH, stressed on the problem of "a big knowledge gap", explaining that the scarcity of randomized controlled trials can put doctors in a tough spot.

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