News Release

Many adults with breast cancer use cannabis but don’t tell their doctors

Survey results suggest that patients need more information from physicians about marijuana’s potential benefits and risks

Peer-Reviewed Publication


New research indicates that almost half of U.S. adults with breast cancer use cannabis (marijuana and hemp), most commonly alongside cancer treatment to manage symptoms and side effects. However, most patients don’t discuss their use of cannabis with their physicians. The findings are published by Wiley early online in CANCER, a peer-reviewed journal of the American Cancer Society.

Individuals with cancer often experience pain, fatigue, nausea, and other difficulties that arise from cancer and its treatment. Some turn to cannabis for relief of their symptoms, but many physicians feel that they lack the knowledge needed to discuss cannabis with their patients. Such knowledge is especially important now that cancer is specified as a qualifying condition in nearly all states with medical cannabis programs.

Investigators recently conducted an anonymous online survey to examine cannabis use among adults who were diagnosed with breast cancer within five years and were members of the and online health communities.

Among the major findings:

  • Of 612 total participants, 42% reported using cannabis for relief of symptoms, including pain, insomnia, anxiety, stress, and nausea/vomiting. Among those who used cannabis, 75% reported that it was extremely or very helpful at relieving their symptoms.
  • Nearly half (49%) of participants who used cannabis believed that medical cannabis can be used to treat cancer itself; however, its effectiveness against cancer is unclear.
  • Among those using cannabis, 79% had used it during treatment, which included systemic therapies, radiation, and surgery.
  • Participants reported using a wide range of different cannabis products known to vary in quality and purity.
  • Half of participants sought information on medical cannabis, and websites and other patients were ranked as the most helpful sources of information. Physicians ranked low on the list.
  • Among those who sought information on cannabis use for medical purposes, most were unsatisfied with the information they received.
  • Most participants believed cannabis products to be safe and were unaware that the safety of many products is untested.

“Our study highlights an important opportunity for providers to initiate informed conversations about medical cannabis with their patients, as the evidence shows that many are using medical cannabis without our knowledge or guidance,” said lead author Marisa Weiss, MD, of and Lankenau Medical Center near Philadelphia, Pennsylvania. “Not knowing whether or not our cancer patients are using cannabis is a major blind spot in our ability to provide optimal care, and 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.”

Dr. Weiss added that patients should never use cannabis as an alternative to standard cancer treatment, and clinicians should inform patients about the safe and effective use of cannabis as an adjunct to their cancer treatment plan.

Additional Information

NOTE: The information contained in this release is protected by copyright. Please include journal attribution in all coverage. A free abstract of this article will be available via the Cancer News Room upon online publication. For more information or to obtain a PDF of any study, please contact:

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Full Citation:

“A Coala-T-Survey of Breast Cancer Patients’ Use of Cannabis Before, During and After Treatment.” Marisa C. Weiss, Julianne E. Hibbs, Meghan E. Buckley, Sherry R. Danese, Adam Leitenberger, Melissa Bollmann-Jenkins, Sam W. Meske, Katherine E. Aliano-Ruiz, Theresa W. McHugh, Sharon L. Larson, Elaine H. Le, Nancye L. Green, Paul B. Gilman, Virginia G. Kaklamani, Rowan T. Chlebowski, and Diana M. Martinez. CANCER; Published Online: October 12, 2021 (DOI: 10.1002/cncr.33906).

URL Upon Publication:

Author Contact: Ella Chick, at or +1 610.642.6550 x105

About the Journal
CANCER is a peer-reviewed publication of the American Cancer Society integrating scientific information from worldwide sources for all oncologic specialties. The objective of CANCER is to provide an interdisciplinary forum for the exchange of information among oncologic disciplines concerned with the etiology, course, and treatment of human cancer. CANCER is published on behalf of the American Cancer Society by Wiley and can be accessed online.

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About Wiley
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