42% of breast cancer patients used cannabis, most during active treatment, and few told their doctors | Research

The takeaway

In a survey of 612 breast cancer patients, 42% used cannabis primarily for pain, insomnia, and anxiety, with 79% using it during active treatment and only 39% discussing it with any physician.

Oncologists, breast cancer patients, and cancer support organizations.

79% used cannabis during active treatment; only 39% told their doctor

What the researchers found

42% of breast cancer patients used cannabis for symptom relief (pain 78%, insomnia 70%, anxiety 57%). 49% of cannabis users believed it could treat cancer itself. 79% used cannabis during active treatment (systemic therapy, radiation, surgery). Only 39% discussed cannabis with any physician.

Why it matters

The high rate of undisclosed cannabis use during active cancer treatment creates potential risks from drug interactions that neither patients nor their oncologists may be aware of.

The numbers in context

612 participants, 257 (42%) used cannabis. Reasons: pain (78%), insomnia (70%), anxiety (57%), stress (51%), nausea/vomiting (46%). 49% believed cannabis could treat cancer. 79% used during treatment. Only 39% discussed with physicians.

How the study worked

Anonymous online survey of US-based Breastcancer.org and Healthline.com members with self-reported breast cancer diagnosis within 5 years (age 18+). 612 participants total, 257 cannabis users.

What this study cannot tell us

Self-selected sample from advocacy websites may overrepresent cannabis-favorable attitudes. Self-reported cancer diagnosis. Online survey may underrepresent older or less internet-connected patients.

How to read the evidence

Moderate: reasonable sample size with detailed survey, but self-selected from advocacy websites.

When this study was published

Published in 2022.

The bigger picture

Nearly half of breast cancer patients using cannabis believe it can treat cancer, a misconception that combined with low physician disclosure rates creates a concerning information gap in oncology.

Questions still open

Does cannabis use during chemotherapy affect treatment outcomes? Why are so few patients discussing cannabis with oncologists? Would oncologist-initiated conversations improve disclosure rates?

Common questions

Why do so few patients tell their doctors?

The study found patients were unaware of potential interactions, perceived cannabis as safe, and sought information from the internet and family/friends rather than healthcare providers.

Is it safe to use cannabis during cancer treatment?

Using cannabis during active treatment (chemotherapy, radiation, surgery) carries potential risks from drug interactions and unknown effects on treatment efficacy. The researchers emphasize the importance of physician-patient dialogue about cannabis use.

Do patients really believe cannabis treats cancer?

Yes. 49% of cannabis-using breast cancer patients believed medical cannabis could be used to treat cancer itself, not just manage symptoms. This belief is not supported by clinical evidence.

Read the original research

A Coala-T-Cannabis Survey Study of breast cancer patients' use of cannabis before, during, and after treatment.

Cancer, 128(1), 160-168

View on PubMed ↗Publisher’s paper ↗

Citation

Weiss, Marisa C; Hibbs, Julianne E; Buckley, Meghan E; Danese, Sherry R; Leitenberger, Adam; Bollmann-Jenkins, Melissa; Meske, Sam W; Aliano-Ruiz, Katherine E; McHugh, Theresa W; Larson, Sharon L; Le, Elaine H; Green, Nancye L; Gilman, Paul B; Kaklamani, Virginia G; Chlebowski, Rowan T; Martinez, Diana M. (2022). A Coala-T-Cannabis Survey Study of breast cancer patients' use of cannabis before, during, and after treatment.. Cancer, 128(1), 160-168. https://doi.org/10.1002/cncr.33906