The way you have described it, confirms that cancer has, indeed, always been with us. Am I right?
Yes I'm sure you are right.
On the one hand there is the 4 billion year old imperative for the genes in every cell to make as many copies of itself as possible. On the other hand multicellular existence requires cells to cooperate and delegate procreation to specialised germline cells.
The details are fascinating. Millions of damaged cells are eliminated every day by a process of apoptosis that leaves no trace. Interestingly the process is triggered by the mitochondria who of course were once free-living bacteria...