Enzymes as prognostic markers and therapeutic indicators in patients with cancer.

An important question in the management of patients with cancer is early identification of the individual who following 'curative' primary therapy will develop recurrence. Another question is which of several alternative treatments is most appropriate. If the patient at risk can be identified early more aggressive and appropriate adjuvant chemotherapy can be initiated to insure remission or longer periods of disease free survival. In this review the role of tissue and/or serum enzyme activities in this regard is considered. Enzymes alone or in combination with tumor markers or other factors may be used. Lactic dehydrogenase (LDH) is perhaps the most common clinical enzyme used in cancer patients for prognostic purposes. It has an important role in germ cell tumors and in association with chorionic gonadotropin and can predict response to therapy and the prospects of remission. LDH is a valuable prognostic marker in lymphoma, leukemia and in colon cancer. Patients can be stratified into treatment protocols based on LDH activity. The stage of cellular proliferation can be evaluated by assay of thymidine kinase in the serum of patients with Hodgkins Disease and in Lymphoma. An important new marker, Cathepsin D in breast tissue may be useful in predicting women with breast cancer who are at risk for early recurrence.