Morphometric analyses of the microvasculature of tumors during growth and after x-irradiation

Morphometric methods were used to investigate changes in the microvasculature of C3H/Bi mammary carcinomas during tumor growth and following single-dose x-irradiation of 6 mm average diameter tumors. Estimates included per cent vascular volume, average vessel diameter, and mean vessel length and surface area per unit volume of viable tumor tissue. Necrotic tissue volume was quantitated also. Changes in vascular parameter estimates, particularly a decrease in vascular surface area, indicated that the microvasculature may become less capable of handling the exchange of essential nutrients at an early stage in tumor growth. Following irradiation, there was a transient improvement in colloidal-carbon-filling of tumor microvasculature, and a change in morphological character of vessels toward that seen in smaller tumors, which may improve capability for exchange of essential nutrients. The results support the conclusion that these quantitative methods are of value in studying time and dose relationships in radiotherapy or chemotherapy, particularly in conjunction with other radiobiological methods.