Using tumor-bearing C(3)H/He mice, in which syngeneic MH-134 tumor cells were transplanted into the back subcutaneously, the possibility of drug-induced splenectomy using cyclophosphamide (CY) and indomethacin (INDO), the timing of chemo- and immuno-therapy, and the usefulness of the combination of surgical splenectomy with immunotherapy were investigated. In patients with gastric cancer, the significance of splenectomy and its combination with immunochemotherapy was also studied.
The administration of CY in mice on day 3 after tumor transplantation in the initial stage of the tumor prolonged the survival time, while INDO under the same condition shortened it only when administered on day 3 after transplantation. The administration of an immunopotentiator, OK-432, prior to CY administration shortened the survival time, compared with that of single administration of CY, whereas the OK-432 administration on day 2 after the administration of CY prolonged the survival time. In the immunochemotherapy in which CY was administered on day 7 after transplantation of tumor and OK-432 was given every two days after additional 2 days, the anti-tumor effect of drug-induced splenectomy was not observed as judged from the tumor proliferating curve, but the splenectomy on day 3 after tumor transplantation, in the initial stage of the tumor, prolonged tne survival time. Similar results were observed, when INDO was used instead of CY. The concomitant splenectomy in the initial stage of gastric cancer resulted in a more effective prolongation of survival time. In the cases with adjuvant immunochemotherapy, preservation of the spleen in advanced cancer and splenectomy in the terminal stage of cancer were found to be preferable for effective prolongation of the survival time.