A controlled study of efficacy of interstitial or external irradiation in a virus-induced brain-tumor model in rats

A model for experimental interstitial radiotherapy using intracerebral D-54MG glioma xenografts in athymic mice

Due to its constant glial morphology and small variability as to tumor location and growth characteristics, the intracerebral D-54MG tumor xenograft provides the predictability and reproducibility needed by models for the study of stereotactic interstitial radiotherapy. Development and results of experimental brachytherapy in an intracerebral human gliomas derived xenograft tumor model are reported. Tumor homogenate prepared from homogenized subcutaneous D-54MG xenografts was inoculated into the frontal lobe of athymic BALB/c mice (nu/nu genotype). The D-54MG glioma xenografts grew at the site of inoculation without intraventricular or subarachnoid spread. The increase of median survival (IMS) was 58.33% for the highest dose (9370 cGy) and 33.3% for the intermediate dose (5654 cGy). In both experiments the survival prolongation was statistically significant (p < 0.05) as calculated by the Log Rank Rest for Kaplan Meier Survival Distributions. In the low dose group (3159 cGy) only a small and not significant IMS was achieved (16.67%). The results of the present investigation demonstrate the accuracy of the stereotactic operative procedure and the efficacy of experimental intracerebral interstitial radiotherapy with I 125 seeds. Using a constant dose rate, experimental interstitial brachytherapy in brain-tumor bearing nude mice was shown to result in a dose dependant survival prolongation for the treated animals. The model may help to optimize the rational basis of clinical brain tumor therapy and is well suited to simulate dose and dose rate related therapeutic effects.