THURSDAY, May 10, 2018 -- Most cancer doctors say they don't know enough about medical marijuana to provide an informed opinion to patients.

Nevertheless, many go ahead and give its use their blessing, a national survey reveals.


Seven out of 10 oncologists surveyed in the United States said they aren't informed enough about the risks and benefits of medical marijuana to recommend its use to patients, according to findings published May 10 in the Journal of Clinical Oncology.

But eight out of 10 cancer doctors said they've discussed medical marijuana with patients in the past year, and 46 percent have gone so far as to recommend its use in cancer treatment.

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This is a "concerning discrepancy," said Dr. Ilana Braun, chief of Dana-Farber Cancer Institute's division of adult psychosocial oncology, in Boston.

"We can think of few other instances in which physicians would offer clinical advice about a topic on which they do not feel knowledgeable," Braun said.

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

However, pot remains an illegal substance under federal law, restricting research opportunities into its effectiveness as a medical treatment. "The scientific evidence base supporting use of medical marijuana in oncology remains thin," Braun said.

To assess how cancer doctors are grappling with this issue, Braun and her colleagues surveyed a nationally representative random sample of 400 oncologists.

The responses revealed that:

RELATED Study: Medical marijuana users likely to use other drugs Only 30 percent of cancer doctors felt sufficiently informed to make recommendations regarding medical marijuana.

About 46 percent recommended its use, regardless.

Of those who recommended its use, 56 percent admitted that they did not consider themselves well-informed enough to have done so.

Braun said more research needs to be done regarding the medical effectiveness of marijuana, as well as potential harmful effects.

For example, patients with immune systems wrecked by chemotherapy could be at increased risk of a fungal infection from pot use, she noted.

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.

The report found conclusive evidence that oral medications containing THC, the intoxicating chemical in pot, can reduce the impact of chemotherapy-induced nausea and vomiting.

But the report found no evidence one way or the other regarding medical marijuana's ability to treat the lack of appetite and wasting caused by cancer.

There's substantial evidence that pot is an effective treatment for chronic pain in adults, but it's not known if marijuana can help fight cancer pain in particular.

Braun's survey found that 67 percent of cancer doctors felt that medical pot could be a useful adjunct to standard pain management, and 65 percent said it could help patients with their lack of appetite.

Dr. Andrew Epstein, an oncologist with Memorial Sloan Kettering Cancer Center in New York City, said doctors may not have a full grasp of the issue, but that should not necessarily cause great concern.

"If oncologists are recommending something which is blatantly unsafe, then that would be one thing. I think marijuana has a lack of evidence behind some things for benefit and may have some downsides, but I do not think marijuana, per se, is a highly risky therapy," Epstein said. "I am less concerned than the authors about this."

In fact, Epstein argues that the debilitating effects of cancer and cancer treatment -- pain, appetite loss, nausea, depression -- "are potentially more debilitating than any potential medication interactions this plant would have with cancer treatments."

Cancer doctors appropriately consider medical marijuana as an adjunct therapy to be used alongside other established treatments, Epstein said.

"Oncologists are welcoming something that might have benefit outweighing harm in their toolbox, along with all the other things they already have," he said.

At the same time, Epstein agrees with Braun that more research and better medical education is needed, so doctors can provide patients the most well-informed advice they can.

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.

More information

The U.S. National Institute on Drug Abuse has more about medical marijuana.

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