Patterns of serial CEA assays and their clinical use in management of colorectal cancer.

Through persistent clinical research efforts, the CEA test has developed into a useful although complex disease monitor for colorectal cancer. Although improved or prolonged survival from its use has not been demonstrated, CEA monitoring may allow more knowledgeable patient management. Several reports indicate that postoperative serial CEA assays may identify patients with early recurrence, especially when assays are done frequently. Patients with elevated pretreatment CEA levels usually showed progressively rising titers before other objective evidence of recurrence was apparent. A progressively rising CEA titer correlated well with recurrent cancer, but a normal CEA could not be used as proof of its absence. Persistently elevated CEA titers post-treatment was caused either by persistent disease or by nontumor-related factors. The CEA assay was not a substitute for clinical follow-up but was an adjunct in the diagnosis of eary recurrence. Patients with elevated CEA levels caused by localized disease treated by radiation therapy demonstrated a marked fall in serial CEA levels if all CEA-producing tumor was localized within the radiation portal. The use of pretreatment CEA values plus the pattern of CEA reponse to irradiation may help in the selection of fulguration versus abdominoperineal resection as primary treatment for rectal cancer. Persistently low serial CEA titers after irradiation therapy correlated with disease control. The use of frequent serial CEA assays in patients treated with chemotherapy compared well with other parameters as a monitor of disease progression or regression. When used with other clinical parameters, serial CEA trends appeared to be a useful adjunct in assessing the effectiveness of chemotherapy. A fall in circulating CEA or the stabilization of a rising titer after starting chemotherapy usually indicated an effective regimen, whereas a rising CEA titer may signal may signal the need to initiate or to change chemotherapy.