Study Finds No Link Between Marijuana Use and Lung Cancer
May 26, 2006
Science Daily/American Thoracic Society
People who smoke marijuana--even heavy, long-term marijuana users--do not appear to be at increased risk of developing lung cancer, according to a study to be presented at the American Thoracic Society International Conference on May 23rd.
Marijuana smoking also did not appear to increase the risk of head and neck cancers, such as cancer of the tongue, mouth, throat, or esophagus, the study found.
The findings were a surprise to the researchers. "We expected that we would find that a history of heavy marijuana use--more than 500-1,000 uses--would increase the risk of cancer from several years to decades after exposure to marijuana," said the senior researcher, Donald Tashkin, M.D., Professor of Medicine at the David Geffen School of Medicine at UCLA in Los Angeles.
The study looked at 611 people in Los Angeles County who developed lung cancer, 601 who developed cancer of the head or neck regions, and 1,040 people without cancer who were matched on age, gender and neighborhood. The researchers used the University of Southern California Tumor Registry, which is notified as soon as a patient in Los Angeles County receives a diagnosis of cancer.
They limited the study to people under age 60. "If you were born prior to 1940, you were unlikely to be exposed to marijuana use during your teens and 20s--the time of peak marijuana use," Dr. Tashkin said. People who were exposed to marijuana use in their youth are just now getting to the age when cancer typically starts to develop, he added.
Subjects were asked about lifetime use of marijuana, tobacco and alcohol, as well as other drugs, their diet, occupation, family history of cancer and socioeconomic status. The subjects' reported use of marijuana was similar to that found in other surveys, Dr. Tashkin noted.
The heaviest smokers in the study had smoked more than 22,000 marijuana cigarettes, or joints, while moderately heavy smokers had smoked between 11,000 to 22,000 joints. Even these smokers did not have an increased risk of developing cancer. People who smoked more marijuana were not at any increased risk compared with those who smoked less marijuana or none at all.
The study found that 80% of lung cancer patients and 70% of patients with head and neck cancer had smoked tobacco, while only about half of patients with both types of cancer smoked marijuana.
There was a clear association between smoking tobacco and cancer. The study found a 20-fold increased risk of lung cancer in people who smoked two or more packs of cigarettes a day. The more tobacco a person smoked, the greater the risk of developing both lung cancer and head and neck cancers, findings that were consistent with many previous studies.
The new findings are surprising for several reasons, Dr. Tashkin said. Previous studies have shown that marijuana tar contains about 50% higher concentrations of chemicals linked to lung cancer, compared with tobacco tar, he noted. Smoking a marijuana cigarette deposits four times more tar in the lungs than smoking an equivalent amount of tobacco. "Marijuana is packed more loosely than tobacco, so there's less filtration through the rod of the cigarette, so more particles will be inhaled," Dr. Tashkin said. "And marijuana smokers typically smoke differently than tobacco smokers--they hold their breath about four times longer, allowing more time for extra fine particles to deposit in the lung."
One possible explanation for the new findings, he said, is that THC, a chemical in marijuana smoke, may encourage aging cells to die earlier and therefore be less likely to undergo cancerous transformation.
The next step, Dr. Tashkin says, is to study the DNA samples of the subjects, to see whether there are some heavy marijuana users who may be at increased risk of developing cancer if they have a genetic susceptibility for cancer.
https://www.sciencedaily.com/releases/2006/05/060526083353.htm
Many oncologists recommend medical marijuana clinically despite not feeling sufficiently knowledgeable to do so
Researchers identified a discrepancy between oncologists' self-reported knowledge base and their clinical practices and beliefs regarding medical marijuana
May 10, 2018
Science Daily/Dana-Farber Cancer Institute
While a wide majority of oncologists do not feel informed enough about medical marijuana's utility to make clinical recommendations, most do in fact conduct discussions on medical marijuana in the clinic and nearly half recommend it to their patients, say researchers who surveyed a population-based sample of medical oncologists.
The study, published today in the Journal of Clinical Oncology, is the first nationally-representative survey of medical oncologists to examine attitudes, knowledge and practices regarding the agent since medical marijuana became legal on the state level in the U.S. Medical marijuana refers to the non-pharmaceutical cannabis products that healthcare providers recommend for therapeutic purposes. A significant proportion of medical marijuana products are whole-plant marijuana, which contains hundreds of active ingredients with complicated synergistic and inhibitory interactions. By contrast, cannabinoid pharmaceuticals, which are available with a prescription through a pharmacy, contain no more than a couple of active ingredients. While considerable research has gone into the development of cannabinoid pharmaceuticals, much less has been completed on medical marijuana's utility in cancer and other diseases. The researchers speculate that the immature scientific evidence base poses challenges for oncologists.
"In this study, we identified a concerning discrepancy: although 80% of the oncologists we surveyed discussed medical marijuana with patients and nearly half recommended use of the agent clinically, less than 30% of the total sample actually consider themselves knowledgeable enough to make such recommendations," said Ilana Braun, MD, chief of Dana-Farber Cancer Institute's Division of Adult Psychosocial Oncology. "We can think of few other instances in which physicians would offer clinical advice about a topic on which they do not feel knowledgeable. We suspect that this is at least partly due to the uncomfortable spot in which oncologists find themselves. Medical marijuana is legal in over half the states, with cancer as a qualifying condition in the vast majority of laws, yet the scientific evidence base supporting use of medical marijuana in oncology remains thin."
The mailed survey queried medical oncologists' attitudes toward medical marijuana's efficacy and safety in comparison with standard treatments; their practices regarding medical marijuana, including holding discussions with patients and recommending medical marijuana clinically; and whether they considered themselves sufficiently informed regarding medical marijuana's utility in oncology. Responses indicated significant differences in attitudes and practices based on non-clinical factors, for instance regional location in the U.S.
"Ensuring that physicians have a sufficient knowledge on which to base their medical recommendations is essential to providing high quality care, according to Eric G. Campbell, PhD, formerly a professor of medicine at the Massachusetts General Hospital, now a professor at the University of Colorado School of Medicine. "Our study suggests that there is clearly room for improvement when it comes to medical marijuana."
To date, no randomized clinical trials have examined whole-plant medical marijuana's effects in cancer patients, so oncologists are limited to relying on lower quality evidence, research on pharmaceutical cannabinoids or research on medical marijuana's use in treating diseases other than cancer.
Of note, additional findings of the current study suggest that nearly two-thirds of oncologists believe medical marijuana to be an effective adjunct to standard pain treatment, and equally or more effective than the standard therapies for symptoms like nausea or lack of appetite, common side effects of cancer treatments such as chemotherapy.
https://www.sciencedaily.com/releases/2018/05/180510162925.htm