The usefulness of cyclophosphamide pretreatment for subrenal capsule assay against human esophageal cancer.

In order to suppress the host immune reaction in subrenal capsule assay (SRCA) using normal immunocompetent mice, the effects of cyclophosphamide (CPM) pretreatment were compared to those obtained after cyclosporine A (CSA) treatment. CPM and CSA suppressed the host reaction until day 6 and day 12, respectively, however, the histological evaluation of the tumors on day 6 revealed no differences between the two groups. The cytotoxicity of CPM in mouse serum against P388 cells was measured to evaluate the residual activity of CPM against the implanted tumor. No cytotoxicity was observed in the serum 36 hours after the CPM injection. In the histological analysis of clinical samples, inflammatory infiltration was observed in only 4 of 25 samples and tumor cell preservation recognized in 27 of 28 samples. A persistence of tumor cells was recognized in the samples rich in tumor cells. Adequate growth of the tumor in the control groups was obtained from 30 of 33 tumors (91 per cent), and the response rates of this assay were comparable to those of prior clinical experiences on each of these drugs. These results indicated the feasibility of SRCA with CPM pretreatment as a predictive test of chemotherapeutic agents for esophageal cancer.