“Cannabis is becoming a more common agent used by cancer patients,” said Steven A. Pergam, MD, MPH, of the Fred Hutchinson Cancer Research Center in Seattle, Washington, who has worked with colleagues to survey patients.11

“We found that about 1 in 5 patients in our survey were using cannabis in some form during their therapy,” Dr Pergam said. Seventy percent of active users surveyed smoked the drug, of whom 50% used a vaporizer. 

Patients use cannabis for a number of reasons, Dr Pergam told Cancer Therapy Advisor. Most, but not all, patients cited physical symptoms, such as pain, appetite stimulation or nausea control, he said. However, the evidence base for benefits remains “thin,” he added.

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“We were surprised that use for neuropsychiatric symptoms, such as stress, coping with their illness and depression, were other common drivers,” Dr Pergam said. “What we hear from patients is that they like the idea of cannabis because it isn’t a ‘drug’ and that it is a natural product.”  

Some patients also said they believe cannabis actually helps treat their cancer, despite the absence of any data supporting such claims. 

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Between 66% and 68% of patients with cancer who use medical marijuana smoke cannabis cigarettes as their mode of delivery, compared with between 11% and 15% who use edibles and up to 16.5% who use vaporizers, according to a 2017 survey.10 

Little is known about why some patients chose to vape cannabis products. Some patients with finger neuropathy can find it difficult to roll cannabis cigarettes or to use lighters. Because some cancer treatments affect insulin pathways, and because some patients with cancer also have diabetes or prediabetes, sugar-laden edibles can also be a problematic way to administer medical marijuana. One patient whose breast cancer is in remission told Cancer Therapy Advisor that the administration of her mTOR inhibitor precludes the use of edibles, for example.

“Cancer thrives on sugar,” Dr Abrams noted. “Cancer doesn’t use oxygen for energy — it uses glucose.”

Some clinicians and public health officials are now advising patients with cancer to avoid e-cigarette use of cannabis products, at least until more is known about the wave of recent hospitalizations and deaths. The CDC is also advising that people not use e-cigarette or vaping products that contain THC.1

But there are also reasons to worry about patients with cancer smoking cannabis, which sometimes harbors molds that can cause life-threatening lung infections.

“In patients with leukemia, those undergoing bone marrow transplant or those with very weakened immune systems, I definitely wouldn’t recommend use, particularly smoking cannabis,” Dr Pergam said. “The new data on vaping-related lung injury is particularly concerning, as severe complications have been reported primarily in patients using vaping [e-cigarette] devices for THC. I think this is more evidence that cancer patients who use cannabis need to be cautious.”

Worse, cannabis might have negative drug-drug interactions with some anticancer agents — and that might be the case regardless of whether it is smoked or vaped.12,13 For example, retrospective research suggests cannabis use during immunotherapy may reduce tumor response rates (although in the study, this reduction had no impact on survival, Dr Abrams pointed out).13

“This is very concerning,” Dr Cyr said. “Patients on immune checkpoint inhibition should not use cannabis.” 

Cannabis hyperemesis syndrome can also be a problem, worsening rather than alleviating nausea and vomiting, Dr Pergam added. “Drug-drug interactions, instability and falls, and other possible complications concern us. It is also worrisome that patients might stop evidence-based medications to take something that is currently unproven.”

For patients whose cancer treatments do not preclude use of cannabis, tinctures or sublingual oils might be an alternative to medical marijuana edibles, cigarettes, or e-cigarette products, Dr Abrams suggested. 

For patients without contraindications, cannabis can be a valuable part of palliation, Dr Abrams noted. “Marijuana is the only antinausea medicine that also improves appetite and helps with pain, sleep, anxiety or depression, and mood in general,” he said.


  1. US Centers for Disease Control (CDC). Outbreak of lung injury associated with e-cigarette use, or vaping, products. Updated November 8, 2019. Accessed November 11, 2019.
  2. Abrams DI. Should oncologists recommend cannabis? Curr Treat Options Oncol. 2019;20(7):59. 
  3. Tang M-S, Wu X-R, Lee H-W, et al. Electronic-cigarette smoke induces lung adenocarcinoma and bladder urothelial hyperplasia in mice. Proc Natl AcadSciUS A. 2019;116(43):21727-21731.
  4. Butt YM, Smith ML, Tazelaar HD, et al. Pathology of vaping-associated lung injury. N Engl J Med. 2019;381(18):1780-1781.
  5. Illinois Department of Public Health. Annual progress report: Compassionate Use of Medical Cannabis Pilot Program Act: July 1, 2017 through June 30, 2018. Published 2018. Accessed October 6, 2019.
  6. Delaware Medical Marijuana Program. Annual report, fiscal year 2018. Published October 2018. Accessed October 6, 2019.
  7. Connecticut State Department of Consumer Protection. Medical marijuana statistics. Accessed November 11, 2019.
  8. New Mexico Department of Health. Medical cannabis program patient statistics, September 2019. Accessed November 11, 2019.
  9. The Harris Poll. American Society of Clinical Oncology (ASCO) 2019 Cancer Opinions Survey. Harris Insights & Analytics, LLC; September 2019. https://www.asco.org/sites/new-www.asco.org/files/content-files/blog-release/pdf/2019-ASCO-Cancer-Opinion-Survey-Final-Report.pdf. Published September 2019. Accessed November 6, 2019.
  10. Pergam SA, Woodfield MC, Lee CM, et al. Cannabis use among patients at a comprehensive cancer center in a state with legalized medicinal and recreational use. Cancer. 2017;123:4488-4497.
  11. Dai H, Richter KP. A national survey of marijuana use among US adults with medical conditions, 2016-2017. JAMA Netw Open. 2019;2(9):e1911936.
  12. Merkle S, Tavernier SS. Cannabis use and bleomycin: An overview and case study of pulmonary toxicity. Clin J Oncol Nurs. 2018;22(4):438-443.
  13. Taha T, Meiri D, Talhamy S, Wollner M, Peer A, Bar-Sela G. Cannabis impacts tumor response rate to nivolumab in patients with advanced malignancies. Oncologist. 2019;24(4):549-554.