FAMILY MEDICINE® COLUMN

By John C. Wolf, D.O.Associate Professor of Family Medicine Ohio University College of Osteopathic Medicine

FAMILY HISTORY OF OVARIAN CANCER MAKES CA 125 TEST OK FOR READER

Question: My mother was diagnosed with ovarian cancer last fall. Unfortunately, she hasn't done very well because the tumor was quite large before it was found. Her doctor said that it could have been diagnosed earlier if a CA 125 test had been done earlier. Why isn't this test done on every woman?

Answer: Cancer is a serious concern for all of us because it touches most families. As a cause of death, cancer is second only to heart disease. And, if we focus just on cancer deaths in women, ovarian cancer ranks fourth -- with only lung, breast and colorectal cancer claiming more victims. About one out of every 70 women will develop ovarian cancer, and the risk increases with advancing age. Though in most cases a specific "cause" can't be identified, there are risk factors that increase a woman's chances of having this disease. A strong family history or a particular genetic abnormality are predisposing factors in roughly 10 percent of the women who develop ovarian cancer. Women who have never been pregnant and those who have used fertility drugs are at greater risk. Additional risk factors have been suggested, but the evidence is not conclusive. These possible risk factors include consuming a high-fat, low-fiber diet, drinking milk, and using talc -- particularly when it is applied directly to the genital area or the underwear every day.

On the positive side, women who have had multiple pregnancies have a lower risk of developing ovarian cancer -- the more pregnancies, the lower the risk. Nursing also has a benefit in risk reduction. Use of birth control pills for one year diminishes the risk by 10 to 12 percent, while taking them for five years reduces the risk by 50 percent. Having a tubal ligation or a hysterectomy affords reduced risk as well.

Now to more directly address your question about CA 125. This test is one of a family of tests called tumor markers, which look for unique chemicals that are present in cancer, and "mark" their presence. Unfortunately, in the case of CA 125, the test produces a lot of what doctors call "false negatives." In about 50 percent of women with a small ovarian cancer, the blood level of CA 125 is normal. This is a "negative" test but it is a "false negative" because the cancer is actually present. Other inaccuracies can occur even when the tumor is much larger. Only about 60 percent of women with large ovarian cancer tumors will have a positive test result.

In addition to false negative results, the CA 125 test also produces false positives. That is, sometimes a woman can have a high level of CA 125 and not have cancer. This is because elevated levels of CA 125 can be caused by non-cancerous ailments such as pancreatitis, kidney disorders and endometriosis. Also, elevated levels can be due to natural conditions such as menstruation and pregnancy.

Let me illustrate by example what these false positive results can mean. In one study, 67 women who had positive CA 125 test results were subjected to ovarian surgery. For the one woman who actually had ovarian cancer and her family, this surgery could have saved her life; however, for all the rest, it imposed unnecessary anxiety, pain and surgical risk. As a result of this and other studies, doctors have determined that CA 125 is useful for following the course of cancer in a woman who has already been diagnosed with the condition, but it is of no value as a screening test for ovarian cancer in the general population.

Since your mother has ovarian cancer, you have increased risk for it. Be sure to have a pelvic examination annually. Your doctor may also want to order a pelvic ultrasound and CA 125. It is because of your increased risk that this test, which is not good for general screening, can be of some value in your case.

"Family Medicine" is a weekly column.

To submit questions, write to: John C. Wolf, D.O., Ohio University College of Osteopathic Medicine, Grosvenor Hall, Athens, Ohio 45701.

Past columns are available online at http://www.FamilyMedicineNews.org.