Interrelation of Animal Tumor Models to the Clinical Problem of the Treatment of Hepatic Metastases

Abstract

After a ‘dormant’ phase of many years the problems presented by liver metastases are again of great interest to both experimental researchers and clinicians. Purely mechanical theories are being replaced by experimentally acquired insights into the biological behaviour of tumor and host. Halsted’s concept was that the metastatic process consisted of separate lymphogenous and haematogenous routes of spread that with time should follow one another. This simple view has been replaced by another; it is now obvious that we are dealing with an expression of a disturbed tumor-host relationship. This does not mean that in daily practice the old theories cannot contribute towards diagnosis and therapy. Here also, Walter’s Theory of metastases based upon the filtering properties of the various capillary beds has been shown to be much too simplistic; yet, it still gives the clinician direction in his search for metastases. The theory can only be considered a ‘rule-of-thumb’; an exception to it is well illustrated by the behaviour of metastasis from breast carcinoma. Walter’s Theory cannot predict why one so seldom sees metastases in skeletal muscle, kidney or spleen, Also why some tumors nearly always and others almost never metastasize.