ABSTRACT
A more natural way of introducing cell population heterogeneity has been presented by Rachev and Yakovlev. They proposed a new criterion of cancer treatment efficiency, i.e., the difference between expected survival probabilities for normal and neoplastic cells, the expectation being taken with respect to the distributions of cell radiosensitivity. Normal and neoplastic cells differ only in their radiosensitivity distributions. It is the survival (clonogenic capacity) of neoplastic and normal cells that completely determines the ultimate effect of treatment. The influence of tumor growth during radiotherapy upon the efficiency of treatment may be considered as negligible. To describe the effect of irradiation in the case of a single exposure, one has to specify the response function.
