Lack of Correlation Between Differentiation Status and Response to Radiation of Three Murine Squamous Cell Carcinomas

The gross growth rate, histology, cellular kinetics, and in situ radiobiological response have been measured for three murine, keratinising squamous cell carcinomas that differed in their degree of differentiation. Growth rate was fastest in the least-differentiated tumour, slowest in the best-differentiated. However, the kinetics of the compartment of undifferentiated cells that are likely to be radiotherapeutically important, were the same for the three lines. There was no correlation between degree of differentiation and intrinsic or apparent radiosensitivity as measured by the growth delay assay. The radiobiologically best-oxygenated tumour was that which has the largest stromal component and this was not the best-differentiated tumour.