A new marker for normal tissue and tumor responses to irradiation in vivo

Impairment of normal tissue is one of the major concerns associated with radiotherapy of tumors. Side effects such as enterobrosia and cognitive problems are reported after exposure to radiation during and after cancer therapy. This study evaluated the ability of 14C-Thymidine for detecting the early effects of irradiation on tumor, gut and skin proliferation-rate. To measured 14C-Thymidine uptake, mice were intravenously injected with tracers. The linear energy transfer (LET) and dose-related decrease in 14C-Thymidine in NFSa tumor were observed 12 hours after carbon-beam irradiation. Furthermore, the reduction in 14C-Thymidine uptake at 12 hours was correlated with tumor-volume at 14 days after irradiation. These findings demonstrated that the thymidine uptake could be an appropriate marker for investigating tumor proliferation-rate after radiotherapy of malignant diseases. Thymidine uptake could predict for or allow for rapid monitoring of response to radiotherapy. (author)