Metastatic cancer leaves marks on the bones. They know this from studying contemporary cancer victims. It’s amazing what can be learned from a well-preserved cadaver.
My theory is that some cancers, such as skin cancer, were just as prevalent in ancient populations, but simply haven’t been identified due to lack of remains and lack of evidence on bones. Other cancers would be less common because of shorter lifespans as well as other lifestyle variations.
Most cancers are in older people...in the past, people died at a younger age so didn’t die of cancer.