[Chemotherapy responsiveness of brain tumors in subrenal capsule assay]

The 6-day subrenal capsule assay for determining chemotherapeutic sensitivities of brain tumors was studied. Rat glioma 9L and ACNU resistant 9L-2 were transplanted under the renal capsule of normal immunocompetent WKA rats for laboratory investigation. Evaluation of implanted tumor growth till 12 days was performed. The effects of chemotherapeutic agents administered intravenously were evaluated by measuring the growth rate of implanted tumor specimens. The results obtained from SRC were compared with the results from colony forming assay. Both were correlated to each other. On the other hand, histological investigation revealed that implanted human tumor cells had been diminished and implanted tumor was replaced by immunoreactive cells from the host in many cases. These results threw doubt on a reliability of SRC. To avoid this immunoreaction, cyclophosphamide was injected as immunosuppressive agent subcutaneously 24 hours before implantation. In such cases, the growth rates of implanted tumors were increased and histologically the implanted tumor cells existed for 6 days after implantation. Twenty-three malignant brain tumors (malignant astrocytomas 16, metastatic tumors 5, malignant lymphoma 2) were obtained as surgical specimens. Evaluable assay rate of our study were 89%. 15 patients with malignant astrocytomas were studied about correlation between the sensitivities of ACNU and post-operative clinical courses. Overall clinical correlation of 15 cases of malignant astrocytomas was 47%. These results from subrenal capsule assay are not seemed to be beneficial for clinical use. Immunoreactive response when using immunocompetent rats must be solved in future.