For tumor markers, there was significant difference for the level of carcinoembryonic antigen (CEA) between CTCs’ positive and CTCs’ negative group (p = 0.002), nevertheless, the significant difference did not exist in the other tumor markers level, such as carbohydrate antigen-153 (CA153), carbohydrate antigen-199 (CA199) and carbohydrate antigen-724 (CA724) (P > 0.05, respectively) (Additional file 7). This evidence concerns the gene CEACAM5 and neoplasm.