CA 19-9 is used to monitor which cancer?

• A. Pancreatic adenocarcinoma
• B. Ovarian adenocarcinoma
• C. Breast adenocarcinoma
• D. Choriocarcinoma

Answer: (A)

CA 19-9 is a tumor marker used primarily to monitor pancreatic cancer. Its levels tend to reflect tumor burden, rising with disease activity and often decreasing with effective treatment or after tumor removal. While it can be elevated in other gastrointestinal cancers and benign biliary or pancreatic conditions, its strongest and most established role is in tracking pancreatic adenocarcinoma. Keep in mind that some people don’t produce CA 19-9 at all due to Lewis antigen absence, so a normal value doesn’t rule out cancer in those individuals. This makes CA 19-9 a useful tool for monitoring known pancreatic cancer rather than a general screening test.