Radiation-induced changes in regional blood flow in human tumors.

In 43 patients the blood flow in 48 superficial metastatic tumors was measured with the 133xenon wash-out method. In all cases the blood flow was measured before the start of radiotherapy and then one week later during radiotherapy. In 36 cases the blood flow was measured after 2 weeks during radiotherapy, and in six patients the follow-up lasted 5-6 weeks. The blood flow increased during the first week of radiotherapy in the whole series from 20.1 +/- 18.0 ml/min/100g to 31.3 +/- 24.9 ml/min/100g. The increase during the first week was significant (p less than 0.001). During the second week of radiotherapy the blood flow decreased to 27.0 +/- 19.3 ml/min/100g; the decrease was also significant (p less than 0.05). The changes in the different tumor groups during radiotherapy seemed to be in the same direction. In a longer follow-up the gradual decrease in the blood flow seemed to continue.