Remember that Cnacer is a BIG BUSINESS. For so long, Big Pharma company hide this truth of cannabis in overcoming Cancer. The reason is simple! They don't want to lose their multi million profit from Cancer business. That Cannabis is Illegal is fully because of the matter of Politic.
Below is a list of 34 studies for the skeptics out there. They are categorized by cancer type and treatment.
Source : http://www.realfarmacy.com/34-medical-studies-for-the-skeptic/