For those patients with distant metastatic disease with serial CEA values drawn while receiving cytotoxic chemotherapy, we found that for 35 participants with documented progression, the mean change in CEA values for patients with documented tumor progression was an increase of 19 ng/ml (range: 12.2 to 176.5 ng/ml), whereas for 23 participants with documented interval disease response, the mean change in CEA values was −7.3 (range: −82.4 to 2.4). The gene discussed is CEACAM5; the disease is metastatic neoplasm.