Furthermore, in subgroup analysis, the sensitivity increased significantly for NAB combined with cytological tumor markers (CYFRA 21–1 and CEA) compared with NAB alone in the diagnosis of adenocarcinoma, whereas, the sensitivity and accuracy were not significantly different between NAB alone and NAB combined with any serum or cytological tumor markers for diagnosing squamous cell carcinoma. Here, CEACAM5 is linked to adenocarcinoma.