An improved rat brain-tumor model

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Abstract
The widely used intracerebral tumor implantation method by freehand injection into parietal or hippocampal areas of the rat brain has proven inadequate for reliable experimental therapeutic studies. Problems include poor intracerebral growth yields and significant rates of spread to extracranial tissues, lungs and spinal cord. Major variables have been examined experimentally on a model using nitrosourea-induced nervous system tumor cell lines in syngeneic rats. A rapid stereotaxic method greatly improved the consistency of tumor placement. The optimal site was the caudate nucleus. The production of a spheroid intracerebral growth was further facilitated by the use of 1% agar in the cell suspension medium and by an injection volume of 10 .mu.l containing at least 104 cells. Further improvements involved injection technique and flushing of the operative field. These modifications have resulted in a 99-100% yield of intracerebral growth, with a marked reduction in the number and size of extracranial extensions and with distant metastasis rates of 0%-5%. These results have continually improved with further experience. The method is satisfactory for radiation and chemotherapeutic trials in which survival time as an index of tumor size may be used as an end point.