Some cells die before they attempt a single replication. This could be due to a disease attack, vulnerable imperfect replicate, plus plus. As long as those that get to replicate can make up the numbers for those that die early. Cells that are resilient and can replicate fast and frequent enough before they die tend to pass on forms of this attribute to their imperfect clones.
With time, many types of cells in the whole protein body get to attempt replications faster and faster. Pure natural selection at work -- a concrete example, smoking kills lung cells, so for the lung cells to maintain their numbers they have to replicate early enough in their life time and frequently.
Most environmental pressures seem to force the biology of the cells in this direction, which increases the likelihood of replication eager cells aka cancerous cells.
That is why at this moment in time, prevention seems bleak.