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A patient recently asked me if she could be screened for ovarian cancer. She had read on the internet that there was a blood test used for early dectection of ovarian cancer and she wanted to know if she could have the test. She’s 25 years old and no one in her family, to her knowledge, has ever had ovarian cancer.
I told her that she could certainly undergo the testing if she wanted to, and that it is a simple blood test. But before deciding, I wanted her to have a little more information, because after she knew more about it, she might not want to be screened.
I told her that the name of the test she was asking about is a CA-125, and that it is elevated in some early ovarian cancers (about 50%) and most advanced ovarian cancers (about 80%). It is also frequently elevated during ovulation and menstruation, and among those with uterine fibroids, endometriosis, PID, or any other condition that irritates the peritoneal surfaces. In about 1% of the general population, it is elevated for no discernable reason. This means that there are lots and lots of false positive tests.
If we find the CA-125 to be elevated, this will trigger a clinical response that would likely include ultrasound scans, CT scans, additional blood tests, and ultimately surgery. The usual findings after surgery are: “Great news! We didn’t find any ovarian cancer!” and that’s because of the many false positive tests. While this is, of course, great news, the downside is that if we hadn’t run the CA-125 test at all, then the patient wouldn’t have needed to have any surgery.
The other major problem with the CA-125 test is that when it is truly positive and the woman really does have ovarian cancer, it is more likely to be an advanced case of ovarian cancer, where we aren’t really dealing with any benefits of early diagnosis. So for both of those reasons, I don’t recommend routine screening of women for ovarian cancer with the CA-125 test.
There is another screening method that has essentially the same limitations, and that is transvaginal ultrasound scanning. By the time the ovarian cancer is large enough to be seen by ultrasound, it usually is no longer limited to the ovary, but has already spread. Further, most of the suspicious things we see in the ovary are not actually ovarian cancer, but benign conditions posing no threat to the patient. Once again, in the event we see something suspicious on ultrasound, following some additional testing, we will likely end up in the operating room removing the suspicious mass. Once again, the most likely findings are: “Great News! It wasn’t ovarian cancer.” And once again, the patient may be left thinking, “but if it wasn’t cancer, why did I need to go through all of this?” For these reasons, I don’t recommend routine screening of all women with ultrasound to detect ovarian cancer.
For a woman with no family history of ovarian cancer, her lifetime risk of ever developing ovarian cancer is about 1%. She can reduce that risk by about half if she has multiple pregnancies, breast feeds her children, or takes oral contraceptive pills for a long time. No one knows why this is true, but most of us presume it to be due to significant suppression of ovulation during her lifetime.
For a woman with one 1st or 2nd degree relative with ovarian cancer, her lifetime risk of ever developing cancer is increased some, but not much…probably to about 3%. But there is another type of family history with a more serious prognosis, those with “family ovarian cancer syndrome.” This much less common situation involves multiple cases of ovarian cancer, particularly at a young age, within the same family. Unlike the sporadic cases of ovarian cancer which represent the bulk of the ovarian cancer we see, the family ovarian cancer syndrome has a solid heredity link, often with the presence of the BRCA1 (about 40% lifetime risk), BRCA2 (about 20% lifetime risk), or Lynch II (about 10% lifetime risk) mutations. Among these populations, screening with either CA-125 or ultrasound has the same problems, although the false positive and false negative rates are different because of the difference in disease prevalence. There is no good data to show that screening these high-risk populations with CA-125 and ultrasound makes any difference in long-term outcome, but I usually recommend screening with both BRCA1 and BRCA2. I feel better and the patient feels better, but I don’t know whether they are really any better off or not.
There are some other ovarian cancer tumor markers that are being investigated now, so stay tuned.
The final issue is if one is going to screen for ovarian cancer, when should the screening begin. Ovarian cancer is rare among younger women and increases significantly with advancing age, particularly after menopause. Many physicians who screen, will do so after age 50, in part because of the increasing incidence of the disease, and in part to avoid the CA-125 fluctuations seen with the menstrual cycle, endometriosis, fibroids and PID, all of which diminish after age 50.
However, a significant number of family ovarian cancer syndrome patients will have already developed ovarian cancer prior to age 50, so for those patients, earlier screening may well be indicated.
