Almost one quarter of patients surveyed at a comprehensive cancer center in the state of Washington, where cannabis is legal, said they had used marijuana within the past year, and almost the same percentage said they had used it within the past month.
“It was unexpected that use was reported among a broad spectrum of patients, spanning all cancer types and age ranges,” Steven Pergam, MD, MPH, assistant professor of medicine, Fred Hutchinson Cancer Research Center, Seattle, Washington, told Medscape Medical News in an email.
“So it is important for providers to ask about cannabis use among their cancer patients ― it’s the first step in being able to engage with them on the topic, knowing that they are using or contemplating using cannabis ― even though we still need more data to help us counsel our patients appropriately,” Dr Pergam cautioned.
The study was published online September 25 in Cancer.
The team carried out a survey of cancer patients attending the Seattle Cancer Care Alliance during a 6-week period between 2015 and 2016. The Seattle Cancer Care Alliance is an ambulatory center for a cancer consortium that includes the Fred Hutchinson Cancer Research Center, the University of Washington, and the Seattle Children’s Hospital.
“A 44-item questionnaire was developed to address cannabis use among cancer patients,” the researchers note. The aim of the survey was to establish the prevalence of cannabis use in their patient population and, among active users, learn what type of product they used, how they used it, and why. Researchers also tested random urine samples for the presence of tetrahydrorcannabinol to validate the prevalence data.
Some 926 patients completed the survey; the majority were male, and the median age of the patients was 58 years.
Survey results showed that 66% of respondents had used cannabis at some point in their life; 24% indicated that they were currently active users.
“Most active users [67%] had used cannabis before their cancer diagnosis,” Dr Pergam and colleagues report; 62% of those who actively used cannabis had told their cancer team about it.
Some patients who had used cannabis in the past had quit by the time they took the survey. More than 80% of those who had quit had stopped using cannabis before being diagnosed with cancer.
A small percentage of former cannabis users quit because of a recommendation from either their oncologist or their primary care physician.
Among those who actively used cannabis, 74% indicated that they used the drug at least once a week, and 56% said they used cannabis on a daily basis. Thirty-one percent indicated that they used cannabis multiple times a day.
Seventy percent of users either smoked cannabis or ingested it through some form of edible product. Dual use was also common, Dr Pergam and colleagues note.
Users who smoked marijuana favored using a pipe to smoke it. For those who ingested cannabis, store-bought candy or other edibles, butters or oils, or homemade baked goods were consumed.
Used Most Often to Alleviate Pain
According to survey results, patients who used cannabis reported that they used it most frequently to alleviate pain.
Dr Pergam noted that patients used cannabis for multiple reasons, not just for pain relief.
“We found it interesting that patients used marijuana to help deal with stress, cope with their illness and depression and not just for physical symptoms,” Dr Pergam said.
Although the researchers expected to see that patients resorted to cannabis to alleviate nausea and to stimulate appetite ― purported benefits of cannabis, according to the lay press ― about one third of survey respondents indicated that they used cannabis for enjoyment.
Active users also indicated that they were more likely than never-users to use cannabis because it was legal (P < .001).
“Even among never users, the respondents indicated substantial interest in learning more about the role of cannabis in cancer care,” the investigators observe.
Despite high levels of interest in learning more about cannabis use in cancer care, most respondents reported that they got their information about cannabis use from sources outside of the healthcare system.
Perhaps disturbingly, more than one quarter of survey participants indicated that they believed cannabis was helping treat their cancer.
“It is important for physicians to emphasize that despite what patients may hear from other sources, data supporting the use of cannabis for controlling cancer-related symptoms or for cancer treatment are limited,” Dr Pergam stressed.
“They want our guidance to make more evidence-based and informed decisions when considering cannabis use,” he added.
Increased Risk of Mold Infections
Asked by Medscape Medical News to comment on cannabis use by cancer patients, John Greene, MD, professor of medicine, Moffitt Cancer Center, Tampa, Florida, noted that he has a special interest in infectious diseases that can occur in the most profoundly immunosuppressed cancer patients, such as those who have undergone transplant, because they are vulnerable to the development of mold infections if they smoke (although probably not ingest) cannabis.
In his own cases series, Dr Greene reported on two male patients with acute myeloid leukemia who presented with nodular patterns in the lungs that resulted from heavy marijuana cannabis use. Two other patients developed a mold infection that was likely due to smoking marijuana.
“The safety of marijuana and its quality is the real issue here,” Dr Greene stressed.
“The other thing with marijuana is that if you smoke it a lot, you can set yourself up for lung cancer and other lung damage, like emphysema, so my take on it at the very least is that profoundly immunosuppressed patients should avoid it,” he added.
If patients do complain of poor appetite and nausea, dronabinol ( Marinol, AbbVie), which is a form of synthetic marijuana in pill form, has been approved by the US Food and Drug Administration for chemotherapy-induced nausea and vomiting as well as for anorexia. It is available even in states where marijuana is not legal.
Dr Greene strongly agreed with the study authors that it is very concerning that such a high percentage of survey respondents believed that cannabis was helping treat their cancer, despite the absence of evidence to support this belief.
“I am sure someone somewhere on Google said that marijuana cures cancer,” Dr Greene observed.
“There’s just a lot of misinformation out, but it is shocking that such a high percentage of these patients said they thought that marijuana was contributing to cure their cancer,” he noted.
Dr Pergam also stressed that profoundly immunosuppressed patients should avoid using cannabis, owing to its potential to cause infections.
“In other patient populations, this needs to be a decision that patients make with their cancer team,” Dr Pergam suggested.
Dr Pergam has received research support from and has been a consultant for Merck Sharp & Dohme Corp, and Optimer/Cubist Pharmaceuticals. Dr Greene has disclosed no relevant financial relationships.
Cancer. Published online September 25, 2017. Full text
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