There is one blood value we deliberately do not offer a test for, and that is CA-125. Not because it is a bad marker, but because outside the consulting room it almost always does the wrong thing: it frightens healthy women and wrongly reassures unwell ones.
That is a strong claim, so let me back it up with numbers.
If you are here because you received a result: breathe out for a moment. A raised CA-125 in most cases does not mean cancer. Below you read why.
What is CA-125?
CA-125 (cancer antigen 125) is a protein found on the cells of, among others, the lining of your abdomen, your ovaries and your womb lining. If that tissue becomes irritated or inflamed, more of this protein enters your blood. Dutch laboratories often use a cut-off around 35 kU/l, although that limit differs per lab.
Note that word: irritated. Not malignant.
CA-125 is not a cancer test. It is a marker that rises when tissue is irritated, and cancer is only one possible cause of that.
What does a raised CA-125 mean?
A raised CA-125 means something is irritating the lining of your abdomen or your ovaries. That can be cancer, but far more often it is something benign: endometriosis, fibroids, a cyst, an infection in your pelvis, or simply your period. Even pregnancy can raise the value. In benign ovarian cysts, a raised CA-125 is regularly measured (Sharma, 2020).
That is why the value is so hard to read on its own.
| Benign cause of a raised CA-125 | Why the value rises |
|---|---|
| Menstruation | The womb lining sheds and irritates the tissue |
| Endometriosis | Inflammation of the abdominal lining caused by endometriosis tissue |
| Fibroids (myomas) | Irritation of the surrounding tissue |
| Benign ovarian cyst | Irritation or inflammation around the ovary (Sharma, 2020) |
| Pelvic infection | An inflamed abdominal lining releases more CA-125 |
| Pregnancy | Especially in the first trimester |
| Conditions outside gynaecology | For example liver disease or heart failure, where fluid irritates the abdominal lining |
Seven rows, and only one of them is the one you would have thought of first. That is exactly the problem with this marker as a standalone test.
Do you have endometriosis? Then a raised CA-125 is the rule rather than the exception. Our pillar endometriosis: symptoms, diagnosis and what blood tests add explains why the marker is not used for diagnosis there either.
Can CA-125 be used to screen for ovarian cancer?
No. That is not our opinion, it has been studied. In a British trial, more than 200,000 women were followed for years, with some screened annually using CA-125 and an ultrasound. After long-term follow-up, screening did not reduce mortality from ovarian cancer (Menon, 2021).
That is one of the largest studies ever done on this subject, and the outcome was disappointing but clear.
This is also why there is no population screening for ovarian cancer in the Netherlands. The RIVM runs population screening for breast, cervical and bowel cancer. Ovarian cancer is deliberately not among them, because there is no test that demonstrably reduces mortality.
Where CA-125 is used is in the hands of a specialist: to better assess an abnormality already seen on an ultrasound, and to follow the effect of treatment in ovarian cancer. Then there is context, and without context the number says little.
Why do we not offer CA-125?
We do not offer CA-125 because outside the consulting room the test does more harm than good. A raised result without context leads to fear and often to investigations that turn out to have been unnecessary. A normal result can reassure you while you have complaints that do need investigating.
That second error is the dangerous one.
Say you are 58, you have been through menopause for three years, and you suddenly lose a little blood. You order a tumour marker, it is normal, and you postpone the appointment with your GP. But bleeding after menopause is assessed with an ultrasound, not with a blood value. We do not want our test to replace that appointment.
So if this is your situation, read: postmenopausal bleeding: why you always get it checked.
What we do offer are panels that answer a question blood can actually answer. The Hormones Women panel for your cycle and your hormones. The Anemia panel when heavy bleeding is making you tired. Neither replaces an ultrasound, and we say so honestly.
What do you do if your CA-125 is raised?
Discuss the result with the doctor who requested it, and look at the whole picture: your complaints, your age, whether you still menstruate and what an ultrasound shows. One raised value says little. Doctors look at the trend across several measurements more often than at a single isolated number.
Above all, do not repeat the test yourself to see whether it "looks better".
These are the questions you can ask your doctor:
- Why was this marker measured in my case, and which question was it meant to answer?
- What does the ultrasound show, and does the result fit with it?
- Are there benign explanations that fit my complaints?
- What is the next step, and when will it be looked at again?
Those four questions give you more to hold on to than any number.
Frequently asked questions
What is a normal CA-125 value?
Many Dutch laboratories use a cut-off around 35 kU/l, but that limit differs per lab and per situation. A value above the limit does not automatically mean something serious is going on. So always discuss a result with the doctor who requested it.
Does a raised CA-125 mean I have cancer?
Usually not. Endometriosis, fibroids, a benign cyst, a pelvic infection, your period and even pregnancy can raise the value. The marker should always be assessed together with your complaints and an ultrasound.
Can I order CA-125 myself as a check?
We deliberately do not offer this marker. Without context a raised result leads to needless fear, and a normal result can wrongly reassure you. In a large trial, screening with CA-125 did not reduce mortality from ovarian cancer (Menon, 2021). If you have complaints, see your GP.
References
- Menon U, et al. Ovarian cancer population screening and mortality after long-term follow-up in the UK Collaborative Trial of Ovarian Cancer Screening (UKCTOCS). The Lancet, 2021. PMID 33991479.
- Sharma D, Vinocha A. Benign ovarian cysts with raised CA-125 levels. Journal of Laboratory Physicians, 2020. PMID 33390678.
- Vilendecic Z, et al. Accuracy of IOTA simple rules, IOTA ADNEX model, RMI, and subjective assessment for preoperative adnexal mass evaluation. Gynecologic and Obstetric Investigation, 2023. PMID 36716716.
- RIVM. Population screening for cancer in the Netherlands. National Institute for Public Health and the Environment. Available via rivm.nl.
- Thuisarts.nl. I have a raised tumour marker in my blood. Dutch College of General Practitioners. Available via thuisarts.nl.
Every blood test result through Lunara includes a professional assessment by a BIG-registered doctor. We do not offer CA-125: always discuss a raised tumour marker with the doctor who requested it.
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