CA 19-9 Radioimmunoassay (RIA)

What is the CA19-9 Radioimmunoassay (RIA) test? What does the CA19-9 test measure?

The CA19-9 Radioimmunoassay (RIA) is a simple blood test that measures the level of tumor-associated antigens found in the blood of a person who has pancreatic cancer. CA 19-9 antigens are foreign substances released by pancreatic tumor cells. CA 19-9 associated antigen is elevated in the serum of patients with pancreatic cancer.

Why is the CA19-9 test performed?

The CA19-9 test is performed periodically to assess the effectiveness of various therapies used in treatment of pancreatic cancer. That is, this test is used to determine if the tumor is progressing, remaining stable, or responding to treatment inside a patient who has been diagnosed with pancreatic cancer. Doctors and healthcare professionals can use the results of CA19-9 tests to help decide whether treatment should be changed, or if additional tests are necessary. It is also used to assess the need to determine if a patient should have an imaging procedure to establish the location of pancreatic cancer recurrence.

How is the CA19-9 test performed?

A simple blood sample is taken from the patient and then sent to a laboratory for testing to determine the level of CA 19-9 present in the blood. This blood sample is measured using an RIA (radioimmunoassay) assay test. The RIA assay is an antibody-based tumor marker test used for the detection of a specific antigen such as CA 19-9. The RIA assay quantifies the amount of tumor antigen in the blood based on the use of a radio-labeled antibody as a "detector" and a "capture" antibody bound to a bead. Units of tumor antigen are then measured using a gamma counter and the resulting values are compared to a standard curve containing known levels of antigen. This comparison results in a measurement of the amount of CA 19-9 present in the patient's blood sample.

How often is the CA19-9 test performed?

Your doctor or member of the healthcare team will determine how frequently the CA19-9 tests should be performed. Often, this test is used to monitor whether the tumor is continuing to grow or progress, despite treatment efforts. In these cases, the CA19-9 test may be repeated on a weekly basis or after each round of chemotherapy or other treatment is completed. Sometimes, the CA19-9 test is used over time to monitor a patient who is not currently receiving treatment, in order to determine if that patient needs to resume treatment or undergo additional testing.

What do the values or numbers of a CA19-9 test mean?

When a patient is tested periodically, the CA19-9 values can be used to monitor progression of the pancreatic tumor. If CA19-9 values increase, then progression or growth of the tumor is indicated. If the values remain the same, then the disease is stable. Finally, if CA19-9 values decrease, then a response to treatment is indicated.

The Food and Drug Administration (FDA) cleared Fujirebio Diagnostics' CA19-9 RIA in May 2002 as the only approved CA19-9 tumor marker assay for pancreatic cancer in the United States with the following statement:
"The Fujirebio Diagnostics CA19-9 RIA is indicated for the serial measurement of CA19-9 to aid in the management of patients diagnosed with cancers of the exocrine pancreas. The test is useful as an aid in monitoring of disease status in those patients having confirmed pancreatic cancer who have levels of serum CA19-9 above the cutoff at the time of diagnosis."

For more information about CA19-9, contact a PanCAN Patient and Liaison Services (PALS) Associate toll-free at 877-272-6226 or by email at pals@pancan.org, or visit Fujirebio Diagnostics at www.fdi.com