ABSTRACT
One of the major challenges in the treatment of cancer is to develop a form of therapy that destroys all cells of the primary tumor. The failure to do so may lead to the development of recurrent tumors. The mechanisms which can restrain the growth of tumor cells and maintain them in a dormant state are divided into active and passive. The identification of the mechanisms responsible for the establishment, maintenance and termination of tumor dormancy have come from studies of animal models. There are three principle mechanisms which have been identified. These are constitutive dependence of tumor cells on growth cells on growth factors; avascularity and sequestration and immunologic restraint. A tumor-dormant state can also result when some of the cells in the tumor are cycling and other cells are being lysed so that the rate of cell proliferation is equal to the rate of cell lysis, with little or no net increase in the tumor mass over time.
