Radiation-induced changes in cell proliferation kinetics in uterine cervix cancer

In vitro double labeling autoradiography for measuring the labeling index, duration of S phase and potential doubling time has been used to assess the effect of a single and fractionated test dose of irradiation in uterine cervix cancer applied in 21 patients. Tumor-labeling index fell significantly in those tumors which had a high labeling index before irradiation, and these cases were found later to exhibit a good radiation response. Duration of S phase which ranged between 9 and 27 hours prior to irradiation was increased. Differences between the potential doubling time and the actual doubling time suggest a massive cell loss in tumors which were, for the most part, of exophytic type. Fractionated irradiation provides more reliable informations than a single dose and is useful for investigation of dynamic changes in the kinetics of an asynchronous cell population.