Experimental evaluation of in situ oncocide for primary tumor therapy: Comparison of tumor‐specific immunity after complete excision, cryonecrosis and ligation

One of the most important recent advances in cancer biology is the demonstration that tumor-specific transplantation immunity (TSTI) to experimental tumors can be induced by a variety of means. Basic to this achievement has been readily available syngeneic tumor-host systems which permit assessment of tumor-specific immunity rather than allograft immunity. While the existence of tumor-specific transplantation antigens (TSTA) in rodents and humans has been clearly demonstrated, little is known about the relationship between the nature and duration of exposure to tumor antigen and the subsequent effectiveness of the host immune response. The studies reported here were designed to test the hypothesis that in situ tumor-cell necrosis (“oncocide”), in addition to being a feasible means of curing primary tumors, increases host response against tumor by immunologic mechanisms. Accordingly, TSTI was assessed: a. after complete excision; b. after regression following cryosurgery or ligation; c. in the presence of large recurrent tumors after cryosurgery; and d. in the presence of large untreated primary tumors. Quantity of primary tumor, transplantation procedures, tumor transplant generation, and animal age were the same in each experiment. TSTI was consistently greater after in situ oncocide by cryosurgery or ligation-release infarction than after complete excision. Animals bearing primary or recurrent tumor were similarly immune. Since in situ oncocide produces greater immunity to subsequent challenge with syngeneic tumor than does excision, an experimental basis in immunology is provided for the clinical results reported after cryosurgical destruction or electrocoagulation of various carcinomas.