Experimental studies of factors influencing hepatic metastases.I. The effect of number of tumor cells injected and time of growth

ERUSAL OF recent reports on cancer re-P search and surgery has revealed a revival of interest in some of the fundamental problems Concerned with the dynamics and biological factors involved in cancer metastasis. In 1955, one of us (E.R.F.)' observed the presence of varying numbers of malignant tumor cells in the venous blood emanating from one-third of 25 colorectal carcinomas examined. Since the possibility existed that such an event might, at least in part, be the result of operative manipulation, the advisability of preliminary venous ligation in the treatment of colorectal carcinoma appeared indicated. Yet, it remained to be demonstrated whether such a procedure would significantly alter the survival rate. Tumor emboli obviously occur in persons not undergoing operative intervention, as attested by the high incidence of hepatic metastases observed at autopsy in patients dying of colorectal carcinoma. Further, tumor cells can be demonstrated, albeit less frequently, in the venous blood of individuals with colorectal carcinoma in whom there is no manipulation of the primary growth during operation.4 The investigation of factors that might play a role in the incidence and growth of hepatic metastases, the commonest cause of death in patients undergoing curative resection for colorectal carcinoma, might hence be of value. The recognition of varying numbers of tumor cells in the venous blood of persons with this type of tumor posed the question of the effect of tumor dosage on the incidence of hepatic metastases.