Nevertheless, determination of alpha-fetoprotein levels is valuable in screening for hepatoma because the serum concentration in patients with this tumor is much higher than in normal adults or in patients with hepatic disturbances from other causes. Determination of CEA levels yields limited diagnostic information because elevated CEA levels are found in some patients with cancers outside the gastrointestinal tract and in others with nonneoplastic inflammatory bowel syndromes. However, an increase in CEA levels in a patient with a known malignant disorder should prompt a search for recurrent or metastatic disease. Measurement of other immunologic products can also provide valuable information. Serum levels of soluble CD27 and CD44 molecules correlate with tumor loads in B cell malignancies.
Monoclonal antibodies can also be of value.
Monoclonal antibodies to various tumor-associated antigens can be labeled with radioisotopes, injected in vivo, and used to monitor the spread of cancer by radionuclide imaging. The concentration of tumor-associated antigens in normal tissues is too low to be detected and thus does not interfere with the interpretation of results. For example, the presence of a nuclear proliferation antigen in diffuse large cell lymphomas heralds a poor prognosis. T cell and B cell acute lymphoblastic leukemias differ in clinical presentation and treatment outcome. Serum levels of CD8 can be used to predict the response of patients with hairy-cell leukemia to interferon therapy.