The most widely used and best characterized blood group antigen-related tumor markers include:
- CA 19-9
- CA 50
- CA 72-4
- CA 242
Each of the above tumor markers have been used with limited success in identifying tumor growth in cancers of the gastrointestinal tract and digestive system, namely colorectal and pancreatic carcinomas. Among these markers, CA 19-9 has been successfully developed into commercially available immunoassays, and will be described in greater detail in the subsequent pages.