Please note that cancer isn't a disease, merely an indication that some cells in our complex bodies have escaped the detection of our immune system. Cancer develops from within your system, where cells for numerous reasons change from aerobic to anaerobic (hence mutate). Our immune system detects and destroys cancerous cells every day, however if your immune system is weak (can be due to an imbalance in your bodies PH levels -> ie too acidic) then some cell mutations will escape its detection and then continue to grow.

Gary has a good chance at reversing the mutated cells using an array of different methods as people here are outlining in the comments.

I'm only new to the SteemIT community, but so far I'm very impressed with how people come together and provide such insightful and helpful information.