George Ohsawa (the founder of macrobiotics in the West) would say that cancer is caused by an unbalanced, unhealthy diet (caused primarily by too much yin foods and drinks.)
I've been reading about and practicing (at my own pace) macrobiotics for about 2 months now. I haven't overcome any illnesses or anything but the whole philosophy and pragmatism of it makes sense to me on an intuitive level.
As far as I know (I haven't checked in depth) there are testimonies of people who have overcome cancer through the practice of macrobiotics. The movie "Healing Cancer From Inside Out" by Mike Anderson I believe contains a couple interviews of people who overcame cancer without any chemo or conventional medication. You can download a torrent of it and watch it for free if you like.
In regards to meditation, there are many different techniques for many different purposes. I use the term "techniques" because I've read that meditation in its truest sense is a state of mind that must be achieved - the techniques can be used to get us there.
There are techniques for visualization, concentration, relaxation (as Wyote mentioned) will power cultivation and some even advertise to be a path to God-realization.
One of the most basic techniques that I learned (that was said to be meditation) is simply sitting in a comfortable position, not lying down so you don't fall asleep, with your eyes closed and being aware of your breath. Be aware as you breath in and as you breath out - don't make any effort to change your breath either - just be aware of it.
I learned this technique while attending a 10-day retreat at a local vipassana center (it was about 4 hours away.) It was completely free - free stay and 2 meals plus a snack each day. I made a measly 20 dollar donation at the end of the program.
The center I attended had been completely run by volunteers since the 80's. I even hitched a ride with a couple other people who were in my general area who were attending the same 10-day course.
Here's the link to their website if you're interested: http://www.dhamma.org/