Kinetic analysis of tumor regression during the course of radiotherapy

A model of tumor regression during the course of radiotherapy is presented, which considered the lethal effect of radiation, the elimination of dying cells and the reproduction of surviving cells. The model was applied to multiple lung metastases in a woman, which were treated with different doses per fraction. The regression of tumor volume was measured from chest radiographs which were taken once a week during the treatment. Radiosensitivity of tumor cells estimated by the model was of D0=150 R and n=5. The half life of dying cells in the tumor was 15 days.