Remember that once famous, long term study in the 60s and 70s that compared a group of rastafarians in Jamaica who had been smoking since birth (the study describes mothers blowing smoke into their babies' cribs to calm them down if they were crying or restless) with a nonsmoking control group to see if it had any measurable effect on their ability to work and fit in to society, and found no difference except that the rastafarians tended to be somewhat better workers?
I think they were talking about the symptoms, not the cancer itself. That said, there are at least a half dozen peer reviewed studies that showed cannabinoids were effective in treating brain, lung and breast cancers. One of the brain cancer studies showed an average reduction in tumor size of about 40%. It's not at all unreasonable to speculate that the reason it's been hard to link marijuana smoking with cancer could be that the cannabinoids counteract the carcinogenic effects of smoke inhalation.
Believe it or not, and it disgusts me to say this, Sanjay Gupta *herk* did a great documentary through CNN on the horrific difference between cannabis treatments and pharmaceuticals for certain diseases in children.
The former Obama advisor's routine is utter bullshit and pretty much writes off the entire history of medicine in the west prior to the 1950s or so. It's hard to say "pharmaceutical companies are conspiring to discredit legitimate treatments because they can't patent and profit from them" without sounding like some hippie conspiracy theorist, but it's also really blatantly obvious that they are.