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It is estimated that one out of four deaths is caused by cancer, making it the second leading cause of death worldwide. Cancer is a chronic disease that involves abnormal cell multiplication, which can disrupt the anatomy and function of an organ. It can start as a small group of abnormal cells that can develop into a solid tumor. In its advanced stages, the abnormal cells can affect neighboring tissues and organs, slough off or break off from the primary tumor, and travel through the bloodstream to seed distant organs, such as the lymph nodes, the brain, the bones and the liver. Death usually occurs from complications involving these affected organs.
The management of cancer, a deadly disease that continues to increase in incidence, usually begins with screening people who are at riskof acquiring the disease. For example, women who have a strong family history of breast cancer, may want to be tested for the disease to be able to catch it as early as possible and decide about treatment options.
On the other hand, screening for cancer in the general population or among people who have a low risk of acquiring disease may have its disadvantages. Some screening procedures, such as an endoscopic procedure to detect colorectal cancer, is not without its risks. Getting false-positive test results can cause anxiety in patients who are made to believe they may have cancer, when in reality they do not have the disease. Similarly, getting a false-negative result may delay treatment in patients who test negative for cancer, if the tumor is not detected immediately.
Can a Simple Blood Test Detect Cancer?
Screening for cancer usually involves evaluation of a person's medical history and physical examination and taking various laboratory tests. These lab exams may include blood tests, urine tests and examination of various tissues and body substances. Blood tests may consist of complete blood counts (CBC), testing for blood proteins, testing for the presence of tumor markers, and more recently, tests for circulating tumor cells (CTC).
A CBC is common test that measures various cell types found in the blood. Blood cancers such as leukemia may be detected by taking a CBC. However, a bone marrow biopsy must be done to confirm the diagnosis of blood cancer.
Testing for abnormal blood proteins such as immunoglobulins by electrophoresis can help detect cancers such as multiple myeloma. However, other tests (i.e, bone marrow biopsy), must be done to confirm the suspected diagnosis.
Blood tests are also used to detect tumor markers, which are chemicals made by cancer cells. Examples of tumor markers include prostate-specific antigen or PSA (prostate cancer) and alpha-fetoprotein or AFP (liver cancer).
This limits their potential for diagnosing cancer.
Therefore, a simple blood test may help screen patients for cancer, but more tests may have to be done to confirm the diagnosis. Recent technologies developed, however, show that blood tests that detect tumor cell DNA may be more helpful in detecting the presence of cancer. More studies have to be done to confirm the accuracy and usefulness of these tests.