[The tumor] grows as though it were a single organism, rather than as a population of dissociated individual cells, each the progenitor of an independent line of tumor cells, as presumably bacteria and other free cells do when inoculated into a new culture medium. This relation suggests further that the host plus tumor represents a new, integrated system of growth whose nature we do not as yet understand.
Anna Kane Laird, Dynamics of tumor growth, British Journal of Cancer (1964)
Now, 50 years on some people still think of cancer cells as independent beings that can be eradicated with toxic enough drugs. I think mathematical modeling can and will aid in pushing the above half-century old perspective on cancer.