Efficacy of intralesional bcg therapy in guinea pigs with disseminated tumor

Abstract

It has been previously demonstrated that transplanted syngeneic tumors established in the skin of inbred (strain‐2) guinea pigs regressed and regional lymph node metastases were eliminated after intralesional injection of viable Mycobacterium bovis (BCG). During the course of this reaction there is the development of tumor‐specific immunity. This experimental model was further manipulated in order that it would more closely approximate a clinical reality. In the present study an evaluation was made of the effectiveness of the developing tumor‐specific immunity in this BCG therapy model, to abrogate artifically induced distant tumor deposits and to assess the requirement for tumor‐specific immunity in the local BCG‐mediated tumor regression. During BCG‐mediated regression of established intradermal tumor, the developing tumor‐specific immunity inhibited the growth of artificially induced vascular metastases in animals receiving a 10* or 105 tumor cell dose. However, there is a direct causal relationship between the distant tumor burden and the escape of skin tumor and regional lymph node metastases from BCG‐mediated regression. Thus, multiple tumor deposits as low as 10* cells are capable of competing for or preempting tumor‐specific immune reactivity, which must be a requirement during some phase of the intralesional BCG‐mediated therapy of established tumor and regional lymph node metastases. Thus, a significant therapeutic effect could be achieved in guinea pigs with established skin tumors and limited vascular metastases when the modality of therapy included BCG intralesional injection, followed 6 weeks later by surgery of the treated skin tumor and regional lymph node. Copyright © 1975 American Cancer Society