I sort of addressed this in a previous comment, if you want to read more. There's actually a book that has your definitive answer, and that's the The Emperor of All Maladies, one of the best pop-medical books I've ever read.

But briefly, cancer is not a new disease; the ancients were aware of it (Edwin Smith papyrus is the first likely mention of cancer, and the Hippocratic corpus deals with cancer explicitly). Prevalence prior to modern times is essentially impossible to figure out; nosology didn't exist in any modern sense, and any number of diseases could present like cancer (especially "pthisis", or tuberculosis). There have been a few paleopathological reports (essentially medical examinations of old bones) that suggest that cancer was far less common in pre-modern peoples. However, this is controversial (this is a great NYTimes articles that nicely outlines the controversy). There are all sorts of methodological reasons this is incredibly difficult to ascertain, and while some risk factors (most notably tobacco smoke and copious red meat consumption) weren't around, there's every reason to believe ancient peoples would have been exposed to risk factors that we don't have (ergot-contaminated grain, open fires, &c).

Sorry for the abbreviated answer, but I hope that helps!