Cell kinetic response of an experimental tumour to irradiation. Use of the stathmokinetic method.

The cell kinetic perturbations following irradiation (20 Gy) were studied by combining the metaphase arrest method using vincristine with histological indices of cell death. The metaphase arrest method yielded remarkably constant values of rate of entry into mitosis (rM) of around 24 new cells/1,000 cells/hour during a 7 day period in which there was no tumour growth. The time course of cell death as indicated by changes in the pyknotic index during this period may reflect the processes of reoxygenation and repopulation known to influence the results of fractionated radiotherapy.