What tumor marker is used to help diagnose liver cancer and monitor the response to treatment?

The correct choice for the tumor marker used to help diagnose liver cancer and monitor the response to treatment is alpha-fetoprotein (AFP). AFP is a protein that is typically produced by the fetal liver, and its levels can be elevated in individuals with liver cancer, specifically hepatocellular carcinoma. This marker is particularly useful because it can assist in both the diagnosis of liver tumors and in monitoring treatment effectiveness or disease recurrence.

In clinical practice, elevated levels of AFP in adults can signify the possibility of liver cancer, especially in patients who have underlying liver conditions, such as cirrhosis or hepatitis. Therefore, AFP is a crucial component in the evaluation process for suspected liver malignancies and is leveraged to track the progress of treatment and response to intervention.

Other options such as CA-125 are primarily associated with ovarian cancer and are not relevant for liver cancer. Similarly, ER/PR (estrogen receptor/progesterone receptor) testing is specific to certain types of breast cancers. None of these markers serve the purpose of diagnosing or monitoring liver cancer, thus reinforcing that AFP is the appropriate choice.