Understanding tumour marker CA125

Overview

The CA125 blood test measures the level of a protein called CA125 in your blood. High levels can sometimes be a sign of ovarian cancer, but they can also be caused by other conditions that are not cancer, such as endometriosis, pregnancy, or a pelvic infection. This test is not used alone to diagnose cancer; it is one part of a larger picture that includes scans and a physical exam.

The CA125 test itself is a common blood test, but having an abnormal result is not common. Most people who have this test either have ovarian cancer or are being monitored after treatment, or have another condition that affects the level.

The test is mainly used in women who have symptoms that could be linked to ovarian cancer, or those already diagnosed with ovarian cancer. It can also be used in some cases for people with endometriosis or other pelvic conditions.

Symptoms

Causes

Main causes

• Ovarian cancer – the CA125 protein is produced by some ovarian cancer cells.
• Endometriosis – a condition where tissue similar to the womb lining grows outside it, which can cause inflammation and raise CA125 levels.
• Pelvic inflammatory disease (PID) – an infection in the female reproductive organs.
• Pregnancy – especially in the first trimester.
• Non-cancerous ovarian cysts or fibroids.

When to see a doctor

See a doctor urgently if:

• If you have symptoms like persistent bloating, pelvic pain, or changes in your toilet habits that are new and last for more than a few weeks.
• If you notice a lump or swelling in your belly area.
• If you have abnormal vaginal bleeding after menopause or between periods.

Book a routine appointment if:

• If you have a family history of ovarian or breast cancer and want to discuss your risk with your GP.
• If you have endometriosis and your doctor recommends monitoring with blood tests.

Diagnosis

A CA125 test is a simple blood test. It is usually done alongside a pelvic exam and an ultrasound scan of your abdomen and pelvis. If the CA125 level is high and other tests suggest something suspicious, your doctor may recommend further imaging like a CT scan or MRI, and possibly a biopsy (taking a small sample of tissue) to confirm the diagnosis.

Tests that may be done

• Blood test for CA125 level
• Transvaginal or abdominal ultrasound scan
• CT scan or MRI of the pelvis and abdomen
• Biopsy (taking tissue from the ovary or other site)

Treatment

Treatment for conditions that cause a high CA125 level depends on the underlying cause. If ovarian cancer is found, treatment often includes a combination of surgery and medication. If the high CA125 is due to a non-cancerous condition like endometriosis or an infection, treatment will focus on managing that condition. Your healthcare team will create a plan tailored to you.

Self-care at home

• Keep a symptom diary to track any changes in your body.
• Maintain a healthy balanced diet and gentle physical activity as you are able.
• Talk to your doctor about any pain or discomfort – there are many ways to manage symptoms.
• Stay informed about your condition and attend all follow-up appointments.

Medical treatments

Medical treatment may include cancer therapies such as chemotherapy (medicines that kill cancer cells), targeted therapies (medicines that attack specific parts of cancer cells), or hormone therapy. For non-cancer causes, treatments might include antibiotics for infections, hormonal treatments for endometriosis, or surgery to remove cysts. Always discuss with your doctor which treatment options are appropriate for you.

Living with this condition

Living with a high CA125 level or ovarian cancer can bring ups and downs. It’s important to follow your treatment plan, go to your check-ups, and talk openly with your healthcare team. You may need to adjust your daily activities during treatment. Let family and friends know how they can support you.

Lifestyle tips

• Eat a nutritious diet rich in fruits, vegetables, and whole grains to help your body stay strong.
• Try to stay as physically active as you feel able – even a short walk can help your mood and energy.
• Get plenty of rest and listen to your body.
• Avoid smoking and limit alcohol intake.

Diet and exercise

Aim for a balanced diet with plenty of plant foods, lean protein, and healthy fats. Gentle exercise like walking, yoga, or swimming can help manage fatigue and improve your sense of wellbeing. Always check with your doctor before starting a new exercise routine, especially during cancer treatment.

Prevention

There is no guaranteed way to prevent ovarian cancer, but certain things may reduce your risk. Using oral contraceptives (the Pill) for several years has been shown to lower the risk. Having your fallopian tubes tied (tubal ligation) or removing the ovaries and tubes (for high-risk women) can also reduce risk. Discuss your options with your doctor.

Screening programmes

There is no routine national screening programme for ovarian cancer in the UK because the CA125 test and ultrasound have not been proven to save lives in women without symptoms. However, women with a very high family risk may be offered regular monitoring. Talk to your GP if you have concerns about your risk.

Complications

If left untreated

• If ovarian cancer is not treated, it can grow and spread to other parts of the body, making it harder to treat.
• High CA125 from an infection or endometriosis could lead to chronic pain or fertility problems if not managed.

Long-term outlook

The outlook for ovarian cancer depends on the stage at diagnosis and the type of cancer. When caught early, many women are treated successfully and live long, healthy lives. Even for advanced stages, treatments have improved greatly, and many people live well for years. Your healthcare team will be honest with you about your individual situation and what you can expect.

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