Cancer is what you'll die of if you manage to survive everything else.
It's really simple: cancer is a catch-all phrase for what happens when your cells start multiplying in a funky way that doesn't allow the rest of your body to survive. It's what happens when your cells go "off plan". There are all kinds of causes for your cell multiplication going "off plan" from viruses to chemicals to sunlight, and there are genetic predispositions for it. In our modern society, some of those causes are exacerbated and some are minimized (cubicle dwellers aren't in much danger of sunlight-caused skin cancer unless they court it, but they're more vulnerable to other kinds of cancer).
Short of nanotechnology where nannites sweep away any off-plan cells away earlier in the process (which is theoretically eventually possible, but then you get into what happens if/when nannites go off plan), we won't cure cancer. Not unless we all start dying so early in our lives from other causes that we don't live long enough for cancer to get us.
IF YOU LIVE LONG ENOUGH, YOU WILL GET CANCER. That's just the statistical reality. Cancer isn't some mysterious, weird disease. It's what happens when the inevitable transcription errors in copying your genetic code so many millions of times happen to result in a cell that is 1.) able to avoid detection by your body's detection and clean-up crew, and 2.) multiplies aggressively. That's it. That's all. The food you eat, the drugs you take, you suntan you get, cups you drink from, the STDs you get (HPV, obviously), the computer screen you sit in front of, the laptop on your balls, your choice in parents, the toxic dump you live next to, the nuclear reactor you work at, etc., all ADD to the chances of one of your cells eventually fitting both the above criteria, but they don't exactly cause it. If you live long enough, you will get cancer. Get that through your heads.
All the hippie dope smoking, natural medicine (hey, Mother Nature doesn't love you: BOTULISM is the most powerful neurotoxin on Earth and it's natural) might help, might hurt. Just like that plastic cup your drinking from and the fabric softener used on the sheets you're sleeping on tonight.
Nanotechnology, or maybe that enzyme they're talking about (that helps your antibodies identify cancer cells, alleviating issue #1) or maybe something like it will help, but it won't be a cure. We are pushing at and hopefully eventually beyond the length of time that the human animal is meant to live. Once we're past reproductive age (which is really ~40, though men are able to keep going for much longer) we're just dead weight in a purely biological sense.
Now here's the kicker: cancer can be a good thing. Some cancer cells are effectively immortal. That's why they're so dangerous. But if we could figure out the sequences that keep them from dying, and applied it to the rest of our bodies...