For example, I know one of the treatments for arthritis is Humira, a monoclonal antibody that suppresses TNF-A (tumor necrosis alpha). It could be the immune system suppresses TNF and this causes the perfect environment for cancers to remain latent.
There should be markers for a “pre-cancer” chronic condition. In multiple myeloma (what my father had) there is a clinical definition of “smoldering” myeloma which I understand to be a pre-cancerous condition. There ought to be more of those