Answer
There are several tests that are useful in detecting cancers in their early stages, when the chance of cures are greatest. Two groups of such tests are genetic tests, and tumor marker tests.
a. Tumor marker tests.
Blood tests for cancer are possible because cancers secrete and release substances that provoke antigenic responses in the body. For example, recurrence of colon cancer cause carcinoembryonic antigen (CEA) levels to rise in the blood. Other diagnostic cancer marker tests include the prostate specific antigen test (PSA test); the CA-125 test for ovarian cancer, and the alpha-feto-protein test(AFP test) for liver cancer.
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b. Genetic tests for cancers
Some genetic tests that are useful in cancer diagnosis include the RET mutant gene test for thyroid cancer; the p16 gene test for melanoma, and the BRCA1 gene for breast cancer. In addition, the microsatellite (DNA fragments) test gives indication of bladder cancer, and telomerase is high in cancer cells -- it enables them to keep dividing.
