Zeng Wang, Shifeng Yang, Hongyang Lu

Serum carcinoembryonic antigen (CEA) is often elevated in lung adenocarcinoma, but not in all patients. Meanwhile, epidermal growth factor receptor (EGFR) mutations and anaplastic lymphoma kinase (ALK) fusion protein are the main driving forces in lung adenocarcinoma. However, whether CEA levels are associated with histologic subtype, EGFR mutations, and ALK fusion remain largely unclear. Preoperative serum CEA levels, postoperative histologic subtypes, and statuses of EGFR mutations and ALK fusion protein were retrospectively assessed in 442 patients with completely resected lung adenocarcinoma treated from January 2014 to December 2015 at Zhejiang Cancer Hospital, People's Republic of China. EGFR mutations were found in 69.9% (309/442) of lung adenocarcinoma patients, and ALK fusion protein in 4.5% (20/442). EGFR mutations occurred more frequently in the lepidic subtype (P=0.001). High preoperative serum CEA levels (CEA >20 ng/mL) were independently associated with EGFR mutations (P<0.001). Moreover, in patients with CEA levels of 21-49 ng/mL, the EGFR mutation rate was 88.2%, which was higher compared to those obtained in the other subgroups. In addition, all specimens were invasive adenocarcinoma, with lepidic (18.6%), papillary (15.4%), acinar (52.7%), solid (9.7%), micropapillary (3.2%), and mucinous predominant (0.4%) subtypes; CEA levels in patients with the solid subtype were higher than those of other histologic subtypes (P=0.001). Preoperative serum CEA levels can serve as a reference marker to identify the histologic subtype, and EGFR mutation or ALK fusion protein status, in lung adenocarcinoma patients. Moreover, histological subtypes could also predict EGFR mutations.