I don't know if it is accurate, but I heard - a good long while ago - that cancer cells lie dormant in the body, until something triggers them...like carcinogens.
I would guess that something like, oh, say a novel virus invading blood cells, just might activate cancer cells. But, I'm no oncologist, or even an Infectious Diseases expert like #FabioCodswallop (sorry, can't remember his real name anymore).