After Woman's Tumor Unexpectedly Shrinks, Her Doctors Wonder If CBD Oil Played a Role

Some outside experts are skeptical, but the woman's doctors say CBD and THC compounds deserve further attention in cancer research.

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 A row of bottles of CBD oil are seen in a branch of the health chain Planet Organic on February 17, 2020 in London, England.
A row of bottles of CBD oil are seen in a branch of the health chain Planet Organic on February 17, 2020 in London, England.
Photo: Leon Neal (Getty Images)

Doctors in the UK say they’ve come across an unusual case of cancer recovery: A woman in her 80s whose lung cancer began to shrink without any conventional treatment, after she started taking daily doses of CBD/THC oil. Though it’s far from clear that the oil actually affected her tumor, the doctors argue that cannabis and its primary ingredients merit further research as a possible cancer treatment.

The CBD in CBD oil comes from cannabidiol, one of the two major compounds found in cannabis. These products can also include delta-9-tetrahydrocannabinol, or THC, the other major compound that’s responsible for the psychoactive effects of cannabis. CBD oil and similar products are in a murky legal market in much of the world. In the U.S., only one medical use of CBD is currently approved, a high-dose version that’s meant to help relieve symptoms in people with certain seizure disorders. But cannabis and CBD oil are permitted to be sold and used in much of the country, as well as in some other countries like the UK.

The patient in this case had experienced a persistent cough for months by the time she visited a doctor in February 2018. By the summer, imaging tests and a biopsy clearly indicated that she had lung cancer, specifically non-small cell lung carcinoma. Though she was a smoker and had preexisting lung problems, doctors felt her case was treatable. But after lengthy discussions, the woman chose to decline options like surgery or radiation therapy. Because of that, the doctors agreed to simply keep an eye on her cancer’s growth through routinely scheduled imaging tests.


Remarkably, the woman’s cancer started shrinking without any intervention on the doctors’ part whatsoever. Compared to the first imaging taken in June 2018, they estimated that the cancer’s size had shrunk 76% by February 2021. In February 2019, after a year of shrinking, the doctors spoke to the woman about her results, and she revealed that she had been ingesting a CBD oil product on the advice of a relative since June 2018, usually at three doses a day. Other than a reduced appetite, the woman reported no side effects from her regimen, and the doctors couldn’t find any other changes to her prescribed medications, diet, or lifestyle (she was advised to quit smoking but had continued to do so) during that time.

“This case appears to demonstrate a possible benefit of ’CBD oil’ intake that may have resulted in the observed tumor regression,” the doctors wrote in their report on the case, published Thursday in BMJ Case Reports.


Some outside experts in the UK are, for the moment, skeptical. In a round-up of comments collected by the Science Media Centre, Edzard Ernst, a retired professor of complementary medicine at the University of Exeter, noted that “case reports cannot be considered to be reliable evidence, and there are currently no data from rigorous clinical trials to suggest that cannabis products will alter the natural history of any cancer.”

Lead author Kah Ling Liew, a doctor in the respiratory department of The Princess Alexandra Hospital, told Gizmodo that the woman is still alive and being actively tracked. As of her most recent check-up this year, the cancer doesn’t seem to have made a comeback and has gotten so small that they can no longer measure its size through the scans she’s getting.


Liew and her colleagues are careful to note that they can’t be sure the woman’s cancer shrinkage was caused by her CBD habit. But they say they can’t find another plausible explanation at this point, either. It is known that cancers can sometimes experience spontaneous regression, where the tumor suddenly shrinks without any clear reason in the absence of treatment, but Liew said that scenario is unlikely.

“Of course we are unable to confirm causation from this single case,” she said. “However, spontaneous regression in such cases are extremely rare. The only difference in this case was the ingestion of the ‘CBD oil.’”


Cannabis is already sometimes used to reduce nausea and other symptoms that result from standard treatments like chemotherapy and radiation. But as the team points out, there has been research looking at the effects of CBD and other cannabinoids on cancer itself, including some showing that they can directly affect the growth and development of tumors. However, they also note that animal studies have been mixed, with some even suggesting that cannabinoids boost tumor growth. In the medical literature, they managed to find one other similar case, where a person with lung cancer also experienced tumor reduction after CBD oil.

In the current case, according to the product supplier, the woman’s oil has an equal mix of CBD and THC. But in the other case, the patient was said to be taking only CBD. So the authors don’t know if this additional THC might have played a role in the woman’s recovery. Right now, there’s a lot of questions left up in the air—questions that at least need more attention and research, according to the authors.


“CBD/THC deserves further study as a primary form or adjunct for cancer treatment as the treatment itself seems to be minimally invasive,” Liew said. Of course, even if CBD/THC could help treat some people’s cancer, the authors wouldn’t expect it to be a panacea for all cancer in general, given how different an individual cancer can be from another. “There will not be a single treatment that works for every form of cancer,” Liew added.

Whether or not cannabis does anything for cancer beyond the nausea relief it can sometimes provide, the authors also feel that more could be done to communicate with patients about any alternative treatments they may decide to take on their own.


“Clinicians need to be aware that their patients may be taking non-conventional and unlicensed treatments without their clinician’s knowledge, and it is always important to consider a patient’s choices when discussing treatment options, i.e., being open and honest about potential benefits and side effects of treatments,” Liew said.

As for the woman herself, she’s understandably happy about her recovery.

“I am ‘over the moon’ with my cancer shrinking, which I believe was caused by the ‘CBD oil’. I am tolerating it very well and I intend to take this treatment indefinitely,” she wrote in an accompanying patient perspective.