http://www.ncbi.nlm.nih.gov/pubmed/15749859

Falleaves, hope you don't mind, but I made your link hot. I think it's important that we have ALL the info. You're not raining on anyone's parade. 

There are also many studies contradicting this. Don't have time to post them alll, but everyone's ability to google is as good as anyone elses.

 Thanks for posting that Fallleaves....it really is important we don't wear blinders in our research.  And to demonstrate what leggo said about there being so many articles out there, there was a recent article from the Huffington Post, in 2012

http://www.huffingtonpost.com/2012/09/19/marijuana-and-cancer_n_1898208.html

....and here is a blurb from the article....

A pair of scientists at California Pacific Medical Center in San
Francisco has found that a compound derived from marijuana could stop
metastasis in many kinds of aggressive cancer, potentially altering the
fatality of the disease forever.

"It took us about 20 years of research to figure this out, but we are very excited," said Pierre Desprez, one of the scientists behind the discovery, to The Huffington Post. "We want to get started with trials as soon as possible."

The Daily Beast first reported
on the finding, which has already undergone both laboratory and animal
testing, and is awaiting permission for clinical trials in humans.

Desprez, a molecular biologist, spent decades studying ID-1, the gene
that causes cancer to spread. Meanwhile, fellow researcher Sean McAllister
was studying the effects of Cannabidiol, or CBD, a non-toxic,
non-psychoactive chemical compound found in the cannabis plant. Finally,
the pair collaborated, combining CBD and cells containing high levels
of ID-1 in a petri dish.

"What we found was that his Cannabidiol could essentially 'turn off'
the ID-1," Desprez told HuffPost. The cells stopped spreading and
returned to normal.

"We likely would not have found this on our own," he added. "That's why collaboration is so essential to scientific discovery."