I'm not sure about cannabis curing cancer, but there's ample research to support that it can help tremendously with the side effects of chemo. Basically, it can make life more comfortable while you go through treatment.
I would advocate, for many reasons, taking regular treatment and cannabis at the same time, but refusing regular treatment because cannabis will do it is a bit over the top. I am a cancer survivor so people tend to talk to me about it.
Yes, there's plenty of evidence for that, I'm not disputing that fact. However, even the most casual search you can find studies testing the effects of cannabinoids in vitro on different cancer types. As I said, the effects are different for each - they respond to different receptors (CB1 and CB2) and have effects ranging from nothing, to halting growth, to promoting cell death and reducing tumour size. The reasons why such differences exist are yet to be researched as far as I can tell though.