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Choriocarcinoma is a rare but highly curable cancer of gestation that is usually detected shortly after pregnancy. A hormone called beta human chorionic gonadotropin (HCG) is present during a normal pregnancy; however, if it is present after a pregnancy, choriocarcinoma is suspected. Therefore, women in whom HCG is detected after pregnancy are often treated for choriocarcinoma with surgical removal of the uterus and/or chemotherapy. Now, researchers in New Mexico caution that false-positive blood tests for HCG are possible and may result in unnecessary treatment in women who, in fact, do not have choriocarcinoma. However, they offer a straightforward solution: test the urine, not the blood, for HCG.

Choriocarcinoma is a cancer that grows from the tissue that is left in the uterus after an abortion or the delivery of a baby. This type of cancer can spread outside the uterus, to other parts of the body. One such type of choriocarcinoma is placental-site trophoblastic disease, which develops where the placenta attaches to the uterus. HCG is present during a normal pregnancy; however, it is not present after pregnancy. If HCG is found in the blood after a pregnancy, choriocarcinoma may be suspected. Treatment is often surgery and/or chemotherapy, depending on the level of HCG, specific type of choriocarcinoma, and stage of disease (extent of disease at diagnosis).

Researchers in New Mexico identified 12 women who unnecessarily underwent treatment for choriocarcinoma after testing positive for HCG in the blood. These false-positive tests occurred because of an antibody in the blood that interfered with the ability to determine the presence of HCG accurately. Fortunately, HCG can also be measured in the urine, where this antibody does not pose such interference.

These researchers concluded that current diagnosis and treatment protocols for choriocarcinoma should be modified to include a test for HCG in the urine. Women who are suspected of having choriocarcinoma may therefore wish to talk with their doctor about a urine test for HCG. (The Lancet, Vol 355, No 9205, pp 712-715, 2000)

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