Effective tumor-cell number and cell kinetic analysis in the prediction of tumor response

Determination of the dose-response relationship in radiotherapy is required for the optimization of cancer treatment. Tumor-cell number and the pattern of cell proliferation are supposed to be major parameters necessary for a proper definition of the dose-response relationship. In clinical practice it is well known that the result after irradiation is inversely related to the size and extent of a tumor - that is, to the tumor-cell burden. However, in experience with H and N tumors, a preirradiation reduction of tumor stage and/or size by chemotherapy does not affect the ultimate control of the disease by means of irradiation. Furthermore, no clear correlation can be found between response to treatment and kinetic parameters such as growth rate, generation time, growth fraction, and cell loss. Recently, cytometric analysis of multiple biopsies has been employed in some H and N tumors to better evaluate their cellular and proliferative characteristics