Immunohistochemical detection of P-glycoprotein and carcinoembryonic antigen in small cell lung cancer: with reference to predictability of response to chemotherapy.

In an attempt to elucidate the tumor properties relating to responsiveness to chemotherapy, we examined immunohistochemically the expression of P-glycoprotein (P-gp) and carcinoembryonic antigen (CEA) in small cell lung cancer (SCLC) tumors. Tumor specimens from 33 patients were obtained at the time of diagnosis and relapse. Four patients expressed P-gp in their initial tumors, and 7 others did in recurrent tumors. The overall response rate to chemotherapy of the initial tumors was 75% for P-gp-positive initial tumors and 86% for P-gp-negative tumors, whereas the disease-free and overall survival times were significantly shorter in the former than the latter. Three patients showed CEA in their initial tumors, and 5 others did in recurrent tumors. The patients with CEA-positive initial tumors tended to relapse earlier than those with CEA-negative tumors. In addition, recurrent tumors expressing CEA were resistant to salvage chemotherapy. A clear correlation between CEA expression by tumors and the CEA level in the serum was observed at diagnosis as well as at relapse. These findings indicate that P-gp and/or CEA expression by a tumor and elevated CEA level in the serum may predict refractoriness of the tumor to chemotherapy.