Many people interpret this life through the lens of science, which is the belief that all things are explainable through a physical process. The problem with this is that you are now explaining things only with physical processes.
I believe in God. I believe that God uses the natural world and can superimpose it also. Remember the story of the Palestinians:
The ark of the Lord was in the country of the Philistines seven months. And the Philistines called for the priests and the diviners and said, “What shall we do with the ark of the Lord? Tell us with what we shall send it to its place.” They said, “If you send away the ark of the God of Israel, do not send it empty, but by all means return him a guilt offering. Then you will be healed, and it will be known to you why his hand does not turn away from you.” And they said, “What is the guilt offering that we shall return to him?” They answered, “Five golden tumors and five golden mice, according to the number of the lords of the Philistines, for the same plague was on all of you and on your lords. So you must make images of your tumors and images of your mice that ravage the land, and give glory to the God of Israel. Perhaps he will lighten his hand from off you and your gods and your land. Why should you harden your hearts as the Egyptians and Pharaoh hardened their hearts? After he had dealt severely with them, did they not send the people away, and they departed?
~1 Samuel 6:1-6
So I believe that guilt is the major cause of cancer but specifically in terms of the holy things of God.
Now let's say someone spends all day every day outside in the sun and say they get skin cancer for it. Here, we see someone getting cancer as a sign of sin but not their own. The sins of the people of the earth have tampered with the holy things of God causing the sky to no longer protect us from the harmful aspects of the sun's rays. So cancer is a sign of sin and an imbalance toward God, especially on the big picture scale, us humans as a whole.