Metastasis--an alternative hypothesis.

The currently accepted models of metastasis are inconsistent with many clinical observations of the natural history of cancer and its response to therapy. Specifically, the authors suggest that it is time for a "paradigm shift." It is time to reject the "local, regional, systemic hypothesis" of cancer and replace it with a hypothesis more consistent with the clinical facts, specifically, that cancer exists in many different forms (i.e. localized disease arising from locally acting carcinogens, which can spread locally and should be treated locally, and cancer that arises as localized disease but evolves to more malignant invasive disease [the current model of metastasis]). The other forms of cancer are systemic disease, which is induced by systemic carcinogens, and cancer arising in multiple cells and multiple sites, giving rise to a picture described as metastatic cancer. The importance of this paradigm shift is that more attention would be focused on identifying systemically acting carcinogens as they relate to etiology and to molecular abnormalities in the neoplastic cells that might be targeted clinically. Recent advances in cancer treatment have demonstrated that molecules that target cancer cell molecular abnormalities (rather than tissue of origin, lymph node, or metastasis) such as bcr-abl or mutations in a cellular receptor such as c-kit or epidermal growth factor possess curative potential. In addition, more attention should be devoted to distinguishing between local tumors and systemic disease, using sophisticated molecular biologic techniques. Perhaps most important, there is a need to devise therapeutic strategies that would treat cancer as a systemic illness and hopefully have a substantial impact on overall cancer mortality.