Hi. As the body uses up protein, ammonia is produced as one of the waste by-products. Ammonia is toxic to the body, so it is processed by the liver into the less toxic substance urea. If the liver is diseased (e.g. liver cancer), it's capacity to detoxify ammonia may be greatly reduced, leading to increased circulating levels of this harmful substance. Increased blood levels of ammonia therefore indicate a worsening of the liver cancer, and possibly liver failure.
Alpha- fetoprotein (AFP) is a substance which is usually found in increased amounts in liver cancer, hence it is considered as a marker for this disease. AFP levels are useful for monitoring the tumor's response to treatment. The levels usually go down if the tumor is responsive to the treatment. If the AFP level remains high even after several cycles of Sorafenib, this may indicate non-response. However, the AFP result has to be correlated with other clinical findings, particularly a repeat liver CT scan (to see if the mass has actually decreased in size after treatment).