IMMUNOTHERAPY

There is evidence to support the concept that the human immune system can be manipulated to elicit an immune response to cancer cells and, at least in some cases, lead to tumor regression (1). The goal of immune therapy is to identify cancer as targets for immune system destruction. The challenge is that tumors are not foreign, but self. Some tumors do have cell surface markers that are unique to tumors, are present in much larger numbers than on normal cells or are normally present only on fetal cells. Such differences are probably the products of normally unexpressed genes. In tumors of viral origin, viral antigens may be present on the cell surface. It is these differences that provide the rationale for cancer immune therapy.

RATIONALE FOR LOCAL IMMUNOTHERAPY OF LIVER METASTASES

There is considerable experience in the treatment of cancer with systemic cytokines; however, there are a number of reasons why local, rather than systemic, administration of cytokines should be considered. Cytokines are normally present at very low levels systemically, but high, non-physiologic levels are necessary for systemic therapy. Some cytokines delivered in this manner can induce severe toxicity. Tolerance is a major barrier to immunotherapy. Direct administration of immunostimulants may alter the local environment and break the immunotolerance created by the tumor cells. In addition, the ischemia-induced necrotic tumor cells from embolization with the concomitant delivery of immunostimulants supply activated antigen-presenting cells with tumor antigens, which may lead to the creation of an in situ cancer vaccine.