A study of 6-day subrenal capsule assay with cyclophosphamide pretreatment--histological evaluation of clinical samples

In order to suppress the host immune reaction in subrenal capsule assay (SRCA), effect of cyclophosphamide (CPM) was evaluated histologically in 25 fresh clinical samples. In 21 out of 25 clinical samples, the extent of lymphocyte infiltration was minimal, and in all samples the host reaction was suppressed significantly by CPM pretreatment. However, tumor cells were well preserved in only 10 out of 20 samples obtained from esophageal cancer patients. With the samples obtained from gastric and colorectal cancer patients, there were no tumor cells in the subrenal space on day 6. Persistence of tumor cells was well recognized in the samples having rich tumor and less stromal cells. The xenografts with moderately to well-preserved cancer cells showed an increase of the tumor size as expressed by delta TS. Though many xenografts showed a positive delta TS, preservation of tumor cells was poor. In each of the drug treated groups, a decrease of the tumor size and the histological effects were well correlated. It is suggested that 6-day SRCA with CPM pretreatment is useful as a chemosensitivity test, especially for the esophageal cancer whose tumor cells were well preserved.