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Medical marijuana has been a hot topic in the United States lately, and we have addressed different perspectives on the issue in recent issues of Oncology & Biotech News
. While I support legalizing marijuana for medical use, one thing not often discussed is what oncologists should do when they live in states where medical marijuana is not legalized if a patient asks about it or acknowledges using the drug, either recreationally or to manage the side effects of cancer or treatment.
As physicians, we need to know if our patients are using any legal or illegal chemicals that might interfere with their treatment or health, so we want to have these conversations. Patients should be reassured that anything they disclose is protected by the laws and ethics guiding doctor-patient confidentiality. We are certainly not going to “rat them out” to anyone, though any drug use should probably be documented in the patient’s chart.
It is important to be truthful with our patients in discussing marijuana use to treat chemotherapy-induced nausea and vomiting (CINV) or pain. Patients should know that smoking marijuana is not nearly as effective as most of the top-line approved therapeutics to treat CINV and pain. There is no solid data we can point to that shows smoking marijuana is more effective than prescribed cannabinoids. Aside fr om the California studies we reported on in the February issue of Oncology & Biotech News
, which were small and have not been confirmed, we do not have studies that tell us much of anything about medical marijuana.
For example, what is the appropriate dosing to treat CINV? How much is needed to treat pain? Is it possible to use too much? A recent study by Soriano-Co et al published in a February 2010 issue of Digestive Diseases and Sciences
reported on 8 patients treated at William Beaumont Hospital in Royal Oak, Michigan, who developed cannabis hyperemesis syndrome. This is associated with chronic marijuana use and symptoms include persistent nausea and vomiting, abdominal pain, and compulsive bathing, which resolved after cessation. Other reports in the world literature confirm this relationship. Appropriate marijuana dose for cancer patients has not been studied in a well-conducted, blinded, placebo-controlled trial.
We know that smoking tobacco is associated with increased risk of recurrence in some cancers and poorer response to treatment; with marijuana, we have no idea how it affects cancer. Could there be toxicities we do not know about? Some studies say marijuana is carcinogenic (though not on par with tobacco), while others suggest it might have anticancer properties. It has also been linked to anxiety and possibly cardiac risks. This is not to say that medical marijuana is unsafe, just that we do not have the supporting evidence to attest to its safety in cancer patients.
It goes without saying that in states where marijuana is not approved for medical use, oncologists cannot help patients obtain it. But once marijuana is put into perspective for patients, they may not feel as enthusiastic about using it before trying legally available drugs. Obviously, patients whose pain and nausea is refractory to approved medications or that have severe side effects fr om currently approved drugs to treat CINV might feel differently. They will have to make the choice over whether to use medical marijuana on their own, but we certainly have an obligation to ensure that we have offered them every legal, FDA-approved remedy available before they make that decision.
Some researchers have called for more federal support for studies to answer questions about the use of medical marijuana in patients with cancer. Before we go there, I think we need to assess patient demand for its use and whether the funds might be better spent elsewhere.