Basic Study of Subrenal Capsule Assay as a Sensitivity Test Against Antineoplastic Agents and Analysis of the Clinical Applicability of This Method for Intracranial Tumors

Abstract

Subrenal capule assay (SRCA) which was first developed by Bodgen et al. has been noted as an in vivo sensitivity test against antineoplastic agents in solid tumors. This method has enabled us to perform a sensitivity test with a small piece of sample and to evaluate the result within a short period. Excellent coincidence of the result of this test with clinical effects has been reported. However, reports of SRCA for brain tumors are rare. Since immunocompetent mice are used in this test, there is a possiblity that host reponse appears even within the limited period of 6 days. Though many investigators manifested their suspicion on the viability of tumors or evaluation of the antineoplastic effect of agents, only a few reports have concerned basic study of SRCA and have investigated the efficacy of this method.
The author experimented SRCA to evaluate the efficacy of this m ethod in immunocompetent ddY mice. A small piece of 19 rat glioma, an established brain tumor cell line, was transplanted into the subrenal space of mice and the survival of the tumor was observed daily. The volume of the tumor and the histological alterations were examined after the administration of antineoplastic agents into mice. Surgical specimens were then used to evaluate the usefulness of this method in clinical cases of brain tumors.
Experimental results showed an increase in the volume of the tumor and infiltration of inflammatory cells even in immunocompetent mice. In the mice receiving cyclophosphamide injection one day before the experiment, the tumor size tended to increase until 12th day and histological examination revealed infiltration of tumor cells into the renal substance and the development of new intratumoral vessels. In the comparison between the mice receiving antineoplastic agents and the mice receiving no antineoplastic agent, the mice with a previous injection of cyclophosphamide showed a distinct difference in the tumor size and were useful for evalution of the antineoplastic effect, compared with those without cyclophosphamide injection.
Clinical results showed that SRCA was easy in tumor such as metastatic br a in tumors for which en bloc resection was available but it was difficult in elastic tumors such as glioma for which only a piece-meal removal was available. Since permeability of antineoplastic agents is disturbed due to the presence of the blood-brain barrier in gliomas, an extended study is necessary before clinical application of SRCA for this kind of tumor.