Studies of marijuana and cancer fall into two groups — those that show it doesn’t cause it and those that show it might cure it.
The most important study in the “doesn’t cause it” category was done by Dr. Donald Tashkin of the UCLA medical school in 2005.
Tashkin studied 1,212 cancer patients — 611 with lung cancer and 601 with head and neck cancers — with 1,040 people without cancer. Both groups contained people who smoked marijuana, tobacco, both or neither.
What he found was that while two-pack-a-day-or-more cigarette smokers had a 20-fold increase in lung cancer risk, pot smokers showed no increase in risk — even among those who had smoked more than 22,000 joints over the course of a lifetime.
What made Tashkin’s study particularly influential was that he had spent a big part of his career trying to prove that marijuana was more carcinogenic than tobacco — and had produced earlier studies showing that pot smoke contained 50 percent more carcinogens than tobacco smoke. His research was often cited in government anti-pot ads as linking marijuana smoking to cancer.
Tashkin’s study isn’t the only one delinking pot smoking and cancer.
In a study published in 1997, Dr. Stephen Sidney at the Kaiser-Permanente HMO examined the files of 64,000 patients compiled over a decade and found that marijuana smokers didn’t develop lung cancer or any other cancer at a higher rate than non-smokers. Like Tashkin, he also found some evidence of a protective effect.
Other studies indicate marijuana could prevent cancer or be used to treat it.
A 1975 study published in the Journal of the National Cancer Institute found that mice implanted with several types of cancer, including leukemia and lung cancers, and then treated with tetrahydrocannabinol (THC) and other cannabinoids had their tumors shrink and life-spans increase.
In 1994, federal researchers gave mice and rats massive doses of THC, looking for signs of cancers and other signs of toxicity. What they found was that the rodents given THC lived longer and had fewer cancers “in a dose-dependent manner” (in other words, the more THC they got, the fewer the tumors).
In 1998, Cristina Sanchez, a biologist at Complutense University in Madrid, found that when C6 glioma brain cancer cells were exposed to THC, they died. Bang, dead.
In 2006, a team of Spanish scientists led by Manuel Guzman administered pure THC via a catheter into the tumors of nine patients with glioblastoma who had failed to respond to standard brain-cancer therapies. There was significant reduction of tumor cell proliferation in all nine test subjects.
In 2007, Dr. Sean McAllister, a scientist at the Pacific Medical Center in San Francisco, published a paper detailing how cannabidiol (CBD) inhibited breast cancer cell proliferation, metastasis and tumor growth.
Also in 2007, Italian investigators described CBD as “the most efficacious inducer of apopthosis (natural cell death; cancer cells don’t experience it and keep multiplying)” in prostate cancer. British rsearchers at Lancaster University said the same thing about CBD and colon cancer.
Last August the National Cancer Institute finally got around to acknowledging on its website that “cannabinoids may be useful in treating the side effects of cancer and cancer treatment” — 40 years after the mouse study published in its own journal alerted them (or should have alerted them) to the possibility.
In his last State of the Union speech, Obama called for a “moonshot” effort to find a cure for cancer — and put Joe Biden in charge of it.
Marijuana remains a Schedule 1 Controlled Substance — deemed by the government to be of no medical value, highly dangerous and largely unavailable for research — because Obama has declined to reschedule it, which he can do with a stroke of his pen.
Biden, who had nearly as much to do with creating and sustaining the war on drugs as Nixon and Reagan, has been an implacable opponent of rescheduling it.
This column does not necessarily reflect the views of Boulder Weekly.