At one level, cancer is very easy to understand.
Cancer is any subset of cells that stop acting in cooperative fashion in support of whole body systems and start using system resources for the purpose of unrestrained growth of that particular line of cells, putting the entire cooperative at risk in so doing.
In that sense, much of the finance industry and many of the governance structures in place in most societies, and many individuals and families, fit the definition of cancer on the body politic.
There seem to be an infinite set of ways in which such strategies can occur, and in the games theoretical sense, all are some variation on the theme of evading the sets of secondary strategies that remove benefit from cheating strategies and allow cooperation within complex populations (like the cells of the human body, or people in modern society) to function.
Ensuring that we have effective strategies that can detect and remove any incentive for cheating strategies to prosper is an essential part of maintaining any level of cooperative. Both Robert Axelrod and Elinor Ostrom developed major conceptual advances in the understanding of the dynamics of such systems.
Cancer as a concept is simple.
The specifics of particular types of cancers, and the specifics of the strategic environment encapsulated in the human immune system are hugely complex topics, just as any particular modern digital computer is a hugely complex assemblage of 7 basic circuits.
Cancer as a concept is relatively simple.
Any specific instance of cancer can be hugely complex, and usually involves several levels of complex interaction with the immune system.
Immune system function in most people is limited by the supply of vitamin C.
Supplying vitamin C in high doses (10s of grams per day) is, beyond any shadow of reasonable doubt, the single most effective thing anyone can do to fight cancer.
Limiting sugar and animal protein intake would be the next two most powerful things.