Tumour colony growth in the irradiated mouse lung.

The effect of irradiation of recipient mouse lung on tumour colony growth after intravenous injection of C3H mammary adenocarcinoma cells or aggregates was tested in C3H male mice irradiated with 14 MeV electrons to the whole or half of the thorax. Injections were made 3 h, 48 h, 3½ months or 9½ months after irradiation.The number and size of colonies were increased in irradiated areas of the lung at 48 h and at 3½ months after doses of 2000 rad. However, 9½ months after irradiation lungs were found to be atrophied and fibrotic and enumeration of tumour colonies was found to be impossible. An increase in colony growth after 250 rad was seen only at 9½ months after irradiation.