CHARLOTTE, N.C. — New survey results reveal many patients with breast cancer smoke, vape or consume marijuana to alleviate symptoms and side effects from treatments — but most of them hide the cannabis use from their doctors.

And the hesitancy goes both ways. Existing research has shown that doctors feel they lack the necessary information to discuss or recommend marijuana use during or after cancer treatment, despite cancer being a qualified condition in nearly all states that have medical cannabis programs.

Of 612 breast cancer patients who completed an anonymous online survey, 39% said they have asked their doctors about marijuana; 76% of these talks were initiated by the patient, mostly those who were older in age. Among this group however, younger patients were more likely to feel supported by their physician, according to the study published Oct. 12 in Cancer, a journal from the American Cancer Society.

In all, 28% of survey respondents said they felt uncomfortable discussing cannabis with their doctors. Researchers speculate the social stigma around using marijuana may be to blame.

Instead, patients are seeking out information on medical cannabis from the internet, other patients, and friends and family, the survey shows. Physicians were among the least likely people patients turned to for advice.

“Not knowing whether or not our cancer patients are using cannabis is a major blind spot in our ability to provide optimal care,” study lead author Dr. Marisa Weiss, chief medical officer and founder of Breastcancer.org, said in a news release. “As healthcare providers, we need to do a better job of initiating informed conversations about medical cannabis with our patients to make sure their symptoms and side effects are being adequately managed while minimizing the risk of potential adverse effects, treatment interactions, or non-adherence to standard treatments due to misinformation about the use of medical cannabis to treat cancer.”

Forty-two percent, or 257 patients, reported using marijuana to relieve their treatment-associated pain, insomnia, anxiety, stress, nausea and vomiting; 75% said cannabis was “extremely or very helpful” and 57% said they couldn’t find any other method that treated their symptoms. The majority of patients reported marijuana use for both medical and recreational purposes, such as relaxation or out of curiosity.

Participants’ average age was 57; 605 were females, five were males and two “preferred not to answer.” Nearly all states were represented in the survey except Montana, North Dakota, South Dakota and Mississippi.

SAFETY CONCERNS

Nearly half of survey participants who used marijuana reported believing that the drug can treat cancer itself, despite no evidence. Doctors say the simultaneous use of cannabis and cancer treatment such as radiation and surgery “raises important efficacy and safety concerns.”

Laboratory studies in test tubes have shown that THC – the psychoactive chemical in marijuana – and CBD, another cannabis ingredient that doesn’t trigger a “high,” can change how the body absorbs cancer medications and cause adverse side effects. However, scientists still don’t know much about how cannabinoids and medications interact in people.

“Nonetheless, an awareness of these risks is important for clinicians and patients,” the researchers said.

ILLEGAL SOURCES

Survey respondents said they used an average of three different cannabis products, such as vapes, liquids and edibles. They also reported getting marijuana from a variety of sources, ranging from state-regulated dispensaries to family, friends and “dealers.”

Researchers say patients who obtain cannabis from unregulated sources risk exposure to contaminants and pathogens, including bacteria, fungi, heavy metals and pesticides. And new research shows some e-cigarettes and vape pens contain vitamin E acetate, a sticky oil additive that can latch onto lung tissue when inhaled. The substance has hospitalized thousands with lung injuries.

Doctors worry lower prices of marijuana from illegal sources compared to higher prices at regulated dispensaries may attract patients to the black market.

“The safest sources of THC cannabis products are state-approved medical dispensaries,” researchers said. “However, these are not available on a widespread basis and usually require patients to obtain certification from an approved clinician.”

Data supports THC’s ability to alleviate chronic pain, including pain caused by cancer, as well as nausea and vomiting from chemotherapy. Studies also show THC can help with insomnia and anxiety.

CBD, on the other hand, is much less researched, so it’s unknown if it offers any beneficial effects for cancer patients.