Blood DNA radiosensitivity may be predictive for efficacy of experimental glioma irradiation: an animal study.

Objective: An animal study was conducted to evaluate the -association between blood DNA radiosensitivity, assessed by determining the original S-index, and the response of experimental gliomas to irradiation. Possible modifications of the latter after administration of iron-containing water (ICW) were also explored.

Methods: The study was performed on Wistar rats with subcutaneously implanted experimental glioma-35. The tumors were locally X-irradiated with a single 15 Gy dose. ICW (60-63 mg·Fe(2+)/l) was administered in the drinking water for 3 days before treatment. The animals underwent blood sampling for analysis of the DNA concentration and leukocyte count. DNA index was estimated 3 days before irradiation and 24 h thereafter. The S-index was evaluated within 4 h before irradiation.

Results: The mean initial S-index in the blood samples of glioma-bearing rats was 0.73 ± 0.05. Addition of ICW in vitro resulted in a significantly increased S-index in half of the samples. In general, the irradiated rats, which had been given pretreatment ICW and demonstrated an in vitro increase of the S-index to >1.0, showed the most marked inhibition of tumor progression and the smallest tumor volume 25 days after irradiation. They also exhibited the lowest rate of lesion growth and the longest survival.

Conclusion: Determination of the biochemical S-index and evaluation of its changes in vitro caused by ICW may be predictive of the response of experimental glioma to irradiation. Because in vivo administration of ICW was associated with a somewhat better tumor response to treatment, it may be considered as a potential radiosensitizer.