Effects of the removal of the primary tumor and immunotherapy with Corynebacterium parvum on metastatic tumor proliferation.

The effects of surgical intervention by removal of the primary focus, and the effectiveness of an immunomodulator, Corynebacterium parvum (Cp), on the proliferation of metastatic tumor tissue were investigated by following the postoperative changes in the 3H-thymidine labelling rate of metastatic tissue in an experimental model of metastasis in mice. In addition, the delayed type hypersensitivity reaction (DTH) was studied to investigate the immune capacity of the host. The labelling rate of mice that had the primary focus removed remained high with little variation, while that of the mice not operated on decreased gradually. On the other hand, in mice undergoing a sham operation, the rate was the same as that of the mice with the primary focus removed for a short while, but then gradually decreased. When Cp was administered, especially before removal of the primary focus, the rate was lower than that of the tumor bearing control group and decreased steadily. The number of pulmonary metastatic nodules was increased by removal of the primary focus, but this increase was inhibited by the administration of Cp which prolonged life. The depression in the DTH was less in the group given Cp preoperativeLy than in either the group of mice having the primary focus removed or those not having it removed.