Cancer Blood Tests
A number of screening blood tests are available to detect the presence of malignant cells. Some tests are able to detect tumor-specific antigens before clinical signs of malignancy become evident. The early detection of cancer can lead to more successful treatment and a better long-term prognosis, so specific and sensitive screening tests can prove vital in the management of cancer.
Cancer Blood Markers
A number of marker chemicals exist which are produced as tumors grow and can be detected in the blood. Some cancer blood markers are produced by wide range of tumors, whereas these are specific to a particular type of cancer. Cancer blood markers can offer an indication that tumors may be present, and patients with elevated cancer marker levels may be recommended for further diagnostic procedures.
Alpha fetoprotein (AFP) can be elevated in liver and testicular cancers, as well as some gastrointestinal cancers. It has been shown to be a good diagnostic test for malignancy in liver tumors, although there are problems with the sensitivity of the test. The marker CA 19-9 is elevated in a number of cancer types, but is a particularly good marker for detecting pancreatic cancer. Carcinoembryonic antigen (CEA) is most frequently used to screen for colorectal cancer in patients with gastrointestinal symptoms, but it is also elevated in a range of other cancers. CA 125 is a widely used tumor marker most often associated with cancers of the female reproductive system, but is also elevated in a range of other cancers. CA 125 is most widely used to monitor the success of treatment in certain types of cancer including ovarian cancer and endometrial cancer.
Antibody Screen Test
The anti-malignin antibody screen test is a useful diagnostic tool for early detection of malignant changes. Malignin is an oncoprotein found in the outer membranes of malignant cells. Anti-malignin antibodies (AMA) are produced by the immune system in response to the presence of malignin, and elevated levels of serum AMA have been demonstrated in patients with a wide range of cancers. The AMA test shows a good sensitivity and specificity, and is therefore a useful tool in the early diagnosis of cancer.
The DR-70 test was developed by AMDL in 1998, and measures the products of degradation of the protein fibrin, which are released into the blood by malignant cells. Fibrin degradation products have been known to be linked with malignancy for many years, with elevated levels having been detected in ovarian tumors as early as 1971. This test has been shown to be effective in the detection of 13 different types of cancer including lung, stomach, breast and rectum cancers, and shows a good level of specificity and sensitivity.
T/Tn Antigen Tests
These cancer blood tests detect the presence of the glycoproteins T and Tn, which are found on the surface of malignant cells. The expression of these antigens can be detected before any malignancies are evident in biopsy. In a study by Georg Springer published in the Journal of Molecular Medicine in 1997, the test detected pre-clinical carcinoma in 77% of patients who later went on to develop malignancies detectable by biopsy or X-ray.
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