There are many tumor markers for the elderly, the more common ones are CEA, CA12-5, CA15-3, CA19-9, AFP, etc. Tumor markers are special proteins that are secreted during the growth process of tumor cells. Tumor markers are special proteins secreted during the growth of tumor cells, which will enter into the bloodstream. Tumor markers can be used for initial screening of various types of cancers through blood screening, and the more common markers in clinic are CEA, CA12-5, CA15-3, CA19-9, AFP, etc. Different markers correspond to different cancers, and abnormally elevated CEA corresponds to different cancers. Different markers correspond to different cancers. Abnormal elevation of CEA may be pancreatic cancer or colon cancer; significant increase of CA15-3 may be considered as breast cancer; elevation of CA19-9 may be caused by colon cancer or rectal cancer; elevation of AFP is mainly related to liver cancer. However, elevated tumor markers do not necessarily mean cancer, and further CT, MRI and pathological tissue biopsy are needed to clarify.