Why Oncologists Should Know More About Medical Marijuana

Oncology FellowsJune 2020
Volume 12
Issue 2

Increasingly, patients are asking oncologists for guidance and recommendations for the use of medical marijuana. However, finding those answers is challenging because of the federal government.

Ashley L. Greenwood, MD

Increasingly, patients are asking oncologists for guidance and recommendations for the use of medical marijuana (MM). Physicians, too, are looking for advice, particularly since much of the information out there is ambiguous such as, “It seems like there is some evidence that MM can be helpful in certain situations, but we just don’t have enough information to be certain.”

In the field of oncology, specifically, MM has a special place of interest with its potential for symptom management and palliation. Anecdotal evidence suggests that MM can alleviate pain, nausea, and loss of appetite—common adverse effects for patients undergoing cancer treatment.

Patients are looking to their providers for answers on MM. Providers, in turn, are looking to their affiliations and governing bodies to fill in the knowledge gaps. However, finding those answers is challenging because of the federal government.

A Brief History Lesson

Cannabis plants are believed to have evolved in central Asia roughly 12,000 years ago. In the years since, marijuana has become the most widely produced and used illicit drug worldwide.1,2 In the United States, however, cannabis wasn’t widely used for recreational purposes until the early 20th century.

The Marihuana Tax Act of 1937 imposed taxes and other administrative burdens on recreational and medical uses of cannabis in the United States. The Supreme Court struck down the Marihuana Tax Act in 1969. Congress subsequently enacted the Controlled Substances Act of 1970, which, among other things, classified marijuana as a schedule I controlled substance. To be categorized as a schedule I, a drug must have high potential for abuse, no accepted use in medical treatments, and a lack of accepted safety for use of the drug under medical supervision.3

There is, however, a history of using marijuana as a medicine. Medicinal marijuana is whole, unprocessed marijuana or its basic extracts formulated to treat symptoms of illness or other conditions. Cannabis extracts were used to relieve stomach pain and vomiting in patients suffering from cholera, rabies, or tetanus as early as the 1800s.2 Today, marijuana and cannabis extracts, both synthetic and natural, have a handful of FDA-approved uses approved including chemotherapyinduced nausea and vomiting, the treatment of anorexia associated with weight loss in AIDS, and seizures.4

These approvals evolved from state initiatives to legalize the medicinal use of marijuana. California was the first state to legalize marijuana for medicinal use when voters approved Proposition 215, the California Compassionate Use Act, in 1996. Despite being illegal at the federal level, at the time of this writing, MM in various forms and for a preponderance of indications is now legal in 33 states—with 47 states allowing use of hemp-derived cannabidiol products with less than 0.3% THC Δ9-tetrahydrocannabinol.5 (Figure 16)

Figure 1. Marijuana Legalization by State6a

In one public opinion poll, two-thirds of Americans say the use of marijuana should be legal.7 Most adults (91%) said marijuana should be legal either for medical and recreational use (60%) or legal for medical use only (32%).

Provider Perspectives on MM

At the University of Oklahoma Health Sciences Center, we have conducted 2 studies looking at provider perspectives on MM. The first was a cross-sectional survey of all oncology providers at the Stephenson Cancer Center in Oklahoma City. We identified 119 possible participants and had a response rate of 34%. We found that most providers do have an interest in prescribing MM (70.7%) compared with having no interest or being unsure (30.3%).8

Despite the high interest in MM, most (76.9%) said they felt they had insufficient knowledge to recommend it. In 2018, Oklahoma passed new laws allowing prescription of MM, but only 7.5% of providers felt they had comprehensive knowledge of the new laws while 35% felt they had no or limited knowledge of the laws. Many providers were looking toward leadership at the medical center and respective governing bodies to guide their decision making. A majority of providers (82%) reported modest to significant increase in patient interest in being prescribed MM since the new laws took effect.

Providers felt MM had the highest chance of improving symptoms such as poor appetite, nausea, chronic pain, and poor sleep. Nearly half (45%) felt that MM could reduce polypharmacy, and 69% felt MM could be beneficial in decreasing opioid dependency in oncology treatments.

The same group also conducted a national, crosssectional survey of Society of Gynecologic Oncology (SGO) members. A total of 203 SGO members completed the survey, with 80% of respondents reporting modest to significant increase in recent patient interest in MM.

No providers believed that interest was decreasing.

Regardless of whether they practiced in a state with or without legalized MM, providers said marijuana should not be listed as a Schedule 1 drug (P = .06). A majority (62.3%) said patients or their families usually initiated the conversation about MM. Most members (65.8%) were looking to their professional organizations such as SGO to provide guidance on MM, as 68.2% of providers felt they did not have sufficient knowledge regarding MM to make recommendations for or against its use.9 (Figure 29)

Figure 2. Symptoms SGO Providers Say MM is Useful for Relieving9

Again, physicians felt that MM could be beneficial to relieve nausea/vomiting (79.2%), poor appetite (83.4%), pain (74.8%), anxiety (64.1%), and insomnia (60.3%). The majority of providers felt that MM was more appropriate for metastatic or advanced cancer (82.3%) rather than early-stage disease (29.7%).

These survey results highlight the dire need for more studies to guide the use of MM in patients with cancer. Both studies showed that oncology patients are increasingly interested in using MM for a variety of conditions.

As a result, providers are under increasing pressure to be knowledgeable about the use of MM and its possible adverse effects. However, many providers feel they lack the resources and training to make informed recommendations for or against the use of MM.

Because laws and approved usage vary from state to state, many oncologists remain hesitant about making recommendations regarding MM. Furthermore, unless marijuana is changed from a Schedule I drug, it will be extremely difficult, if not impossible, to complete highquality clinical studies that will provide the answers oncologists seek.


1. Cannabis. World Health Organization. Accessed March 15, 2020. who.int/ substance_abuse/facts/cannabis/en/

2. Blaszczak-Boxe A. Marijuana’s history: how one plant spread through the world. LiveScience. Published October 17, 2014. Accessed May 3, 2020.

3. Mead A. Legal and regulatory issues governing cannabis and cannabisderived products in the United States. Front Plant Sci. 2019;10(6):697. doi:10.3389/fpls.2019.00697

4. Goldenberg M, Reid MW, IsHak WW, Danovitch I. The impact of cannabis and cannabinoids for medical conditions on health-related quality of life: a systematic review and meta-analysis. Drug Alcohol Depend. 2017; 174(5):80-90. doi:10.1016/j.drugalcdep.2016.12.030

5. State medical marijuana laws. National Conference of State Legislators. Published June 25, 2019. Updated March 10, 2020. Accessed March 15, 2020.

6. DISA Global Solutions. Map of marijuana legality by state. Accessed May 27, 2020. disa.com/map-of-marijuana-legality-by-state

7. Daniller A. Two-thirds of Americans support marijuana legalization. Pew Research Center. Published November 14, 2019. Accessed March 15, 2020. https://www.pewresearch.org/fact-tank/2019/11/14/americans-support-marijuana-legalization/

8. Greenwood A, Castellano T, Jordan B, Richardson DL. Perspectives on medical marijuana; a look at Society of Gynecologic Oncology members. Paper presented at: SGO 25th Annual Winter Meeting; February 6-8; 2020; Snowmass, CO.

9. Greenwood A, Castellano T, Jordan B, Richardson DL. Provider perspective on medical marijuana. Gyn Oncol. 2019;153(3):e17. doi:10.1016/j.ygyno.2019.03.145

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