Daniel Horowitz forwarded me this article which is worth quoting as it supports the complex systems (and somatic evolution) view of cancer.

Relevant quotes:

What this means is that most of these patients are unnecessarily exposed to chemotherapy or radiation, which can have significant side effects or even worsen the disease….

…

Traditionally, doctors have assumed that metastasis occurs when a primary tumor grows so large that it develops characteristics allowing cells to invade other tissues in the body. However, the April issue of Nature Reviews Cancer offers a wholly different concept of metastasis that suggests it may occur much earlier in the course of the disease, when the tumor is small. Under this theory, tumor cells from even a small tumor migrate to other sites in the body, then develop traits that allow them to grow and survive. The theory is presented in a report by Christoph Klein of the University of Regensburg, Germany.