Change in volume of irradiated human metastases. Investigation of repair of sublethal damage and tumour repopulation.

Twenty-one patients, each having at least one metastasis per lung were investigated. A single dose of 1000 rad was delivered to the metastasis located in one lung. while the metastasis located in the other lung received 2 doses of 500 rad separated by a 3-hour interval. The changes in volume of the irradiated metastases were followed at least until the metastases reattained their initial volume. By comparing in each patient the effects of the 2 types of exposure it was possible to estimate the extrapolation number, n, of the survival curve of the tumour cells. In spite of many sources of inaccuracies, it seems possible to conclude that n is not very high, probably smaller than in many normal tissues.Furthermore this work demonstrated, in practically all the tumours studied, an acceleration of the growth rate of the metastases after irradiation.