Significance of tumor volume and blood flow in tumor control by radiation

The mean rate of blood flow in C3H/He mouse mammary carcinoma determined by the clearance of 133Xe was 0.1 ml/g/min in tumors greater than approximately 2.0 cm3, and then blood flow became increasingly greater as the tumor size decreased further. The dose required to produce lethal damage in the tumor increased with the size of the tumors. In large tumors the control rate increased with increasing doses to a maximum at a certain level; at higher doses the rate was somewhat decreased. The present experiments show that changes in blood flow could account for radiosensitivity of the tumor, and a tumor larger than a certain volume can no longer be controlled by a single dose of radiation.