Blood test cancer

To assist in the diagnosis of cancer, your doctor may order specific cancer blood tests or other laboratory procedures, such as an analysis of your urine or a biopsy of an area that appears suspicious. These procedures can help guide your doctor through the cancer diagnosis process.

In most cases, with the exception of certain types of blood cancers, blood tests cannot definitively determine whether you have cancer or some other noncancerous condition, but they can provide your doctor with important information about what's going on inside your body.

Because your doctor has ordered cancer blood tests to check for signs of cancer, it does not necessarily follow that you have been diagnosed with cancer and that you are suffering from it. Find out what your doctor may be looking for when performing cancer blood tests on your body.

What your doctor is looking for
A laboratory examines samples collected for cancer blood tests to look for signs of the disease. Cancer cells, proteins, and other substances produced by cancer may be found in the samples. As well as providing information about how well your organs are functioning, blood tests can also reveal whether or not they have been affected by cancer.

The following are examples of blood tests that are used to diagnose cancer:

Completion of a complete blood count (CBC) is a standard blood test that measures the amount of various types of blood cells present in a sample of your blood. This test may be used to detect blood cancers if an abnormal cell or a large number of a particular type of blood cell or abnormal cells are found. A bone marrow biopsy may be necessary to confirm the presence of blood cancer.

Testing for protein in the blood
In people with multiple myeloma, a blood test to examine various proteins in your blood can aid in the detection of specific abnormal immune system proteins (immunoglobulins) that are sometimes elevated in the bloodstream. Another type of test, such as a bone marrow biopsy, is performed in order to confirm a previously suspected diagnosis.

Tumour marker tests
Known as tumour markers, these chemicals are produced by tumour cells and can be detected in the bloodstream. However, tumour markers are also produced by some normal cells in your body, and levels of these markers can be significantly elevated in noncancerous conditions as well. This reduces the likelihood that tumour marker tests will be helpful in the diagnosis of cancer. It is only in the most extreme of circumstances that such a test would be considered sufficient to make a definitive cancer diagnosis.

It has not yet been determined how to use tumour markers to make a cancer diagnosis in the most effective way. Furthermore, the use of specific tumour marker tests is up for debate.

Prostate-specific antigen (PSA) for prostate cancer, cancer antigen 125 (CA 125) for ovarian cancer, calcitonin for medullary thyroid cancer, alpha-fetoprotein (AFP) for liver cancer, and human chorionic gonadotropin (HCG) for germ cell tumours, such as testicular cancer and ovarian cancer, are examples of tumour markers.

Circulating tumour cell tests
Blood tests that have recently been developed are being used to detect cancer cells that have broken away from their original cancer site and are floating in the circulatory system. For people with breast, colorectal, or prostate cancer, the Food and Drug Administration has approved one circulating tumour cell test for use in monitoring their disease. This test isn't commonly used in a clinical setting because of its complexity.