Usefulness of carcinoembryonic antigen in the diagnosis of small cell lung cancer combined with adenocarcinoma

Background. Small cell lung cancer (SCLC) includes pure SCLC and SCLC combined with other pathologies (C-SCLC). C-SCLC accounts for about 28% of all SCLCs subjected to surgical resection, but only about 1-3% of C-SCLCs are detected by biopsy. Since less than 5% of SCLC patients are eligible for surgery, it is necessary to develop alternative methods for the detection of C-SCLC. Objectives. We determined whether serum carcinoembryonic antigen (CEA) levels, which are usually elevated in lung adenocarcinomas, could be used to differentiate between pure SCLC and SCLC combined with adenocarcinoma. Material and methods. We reviewed the records of 41 SCLC patients (35 with pure SCLC, 6 with C-SCLC) who underwent surgical resection between 2000 and 2014 in Zhejiang Cancer Hospital. Their preoperative serum CEA levels were noted, and the relationship between CEA level and the type of SCLC was analyzed. Results. Serum CEA levels >6ng/mL were found more frequently in C-SCLC patients than in pure SCLC patients (p = 0.031). No such difference was observed when a CEA cut-off of 5ng/mL was used (p = 0.316). Conclusions. A preoperative serum CEA of >6ng/mL may be used as a reference in the diagnosis of SCLC combined with adenocarcinoma.