Immunocytochemical staining for CEA in small cell carcinoma of lung predicts clinical usefulness of the plasma assay.

Recent studies have shown plasma CEA levels are useful in both staging and monitoring response to treatment in patients with small cell cancer of the lung (SCCL). CEA elevations do not occur in all patients however, and have been of less value in patients with limited disease. Immunoperoxidase staining for CEA performed on tumor tissue from 48 patients (17 extensive, 31 limited disease) with SCCL revealed: (1) A strong correlation between positive CEA tissue staining and plasma CEA elevation. Plasma CEA elevations occurred in 18/21 CEA tissue positive patients and correlated with the clinical course in all 18. In contrast elevated plasma CEAs were seen in only 3/27 CEA tissue negative patients; (2) CEA tissue positive patients had a higher incidence of extensive disease (62% versus 18%) and a higher incidence of liver metastases (43% versus 7%); and (3) No correlation between histologic subtype and CEA tissue staining was apparent.