Perioperative immunoactivation with OK-432 pretreatment reduced the incidence of liver metastasesdevelopedin rats given injections of tumor cells. We believe that the perioperative period is critical for the implantation and growth of metastasesand that correction of periopera

Major intraabdominal operations result in immunodepression.In ad dition, manipulation of malignant tumors may release tumor cells into the systemicandportal circulation. The additiveeffectsof immunodepres sion and tumor cell releaseduring surgical treatment for gastrointestinal cancer may increase the metastases of tumor to the liver. We, therefore, studied the inhibitory effect of immuiloactivator OK-432 on the growth of the liver metastasesin the perioperativeperiod usinga model in which rat ascites hepatoma AH-130 cells transplanted into the portal venous systemconsistently induce hepatic metastases.Forty-four male Donryu rats wereassignedto a test group and a control group. The test group of 24 rats was treated with OK-432 (03 mgjday administered i.p.) for 7 days before tumor implantation, and the control group of 20 rats was treated with 0.2 ml of saline i.p. for the samenumberof days as the test group. The number of hepatic metastatic lesionsat 14 days after tumor implantation amountedto 713 ±45.9 (SD) in the test group of 8 rats and 149.3 ±61.9 in the control group of 8 rats. The mean values of survival daysafter tumor implantation in the test group of9 rats and the control group of6 rats were33.4 ±8.1 and 21.8 ±6.9, respectively.The valuesof OKT4@in peripheral blood T-cell subsetsin the test group of 7 rats and in the control group of 6 rats were 51.9 ±7.0 and 41.8 ± 7.2%, respectively. These data showed significant differences between the two groups. Perioperative immunoactivation with OK-432 pretreatment reduced the incidence of liver metastasesdevelopedin rats given injections of tumor cells. We believe that the perioperative period is critical for the implantation and growth of metastasesand that correction of periopera tive immunodepressionmay favorably affect the developmentof meta static diseaseandsurvival. This modelmay haverelevanceto the adjuvant treatment of human gastrointestinal cancer.