In this regard, the already known blood-based protein biomarkers such as [27–34] carcinoembryonic antigen, carbohydrate antigen 19-9 l and α-fetoprotein alone are unreliable as well as lack the sensitivity and specificity needed for early diagnosis of cancer [27–34], which underscores the importance of identifying and validating more sensitive and accurate markers [27]. This evidence concerns the gene CEACAM5 and cancer.