Distinction of ALK fusion gene‐ and EGFR mutation‐positive lung cancer with tumor markers

Abstract Background It is difficult to predict gene mutations individually based on clinical background alone. Tumor markers may help to predict each gene mutation. Identifying tumor markers that can predict gene mutation will facilitate timely genetic testing and intervention. Methods We selected 134 cases of advanced or recurrent ALK‐positive and 172 cases of advanced or recurrent EGFR‐positive lung cancer from our clinical database. The cutoff values for the tumor markers were defined as 5.0 ng/mL or higher for carcinoembryonic antigen (CEA) and 3.5 ng/mL or higher for soluble fragment of cytokeratin 19 (CYFRA21‐1) in accordance with the institutional standards. A positive CYFRA21‐1:CEA ratio was defined as 0.7 or higher. Results The CEA‐positivity rate was 49% for ALK‐positive lung cancers and 73% for EGFR‐positive lung cancers, which was significantly different (p