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

Common symptoms

• Persistent bloating (feeling full or swollen in the tummy)
• Feeling full quickly when eating
• Pelvic or abdominal pain that does not go away
• Needing to urinate more often or urgently
• Changes in bowel habits (like constipation or diarrhoea)
• Unexplained weight loss

Symptoms in children

• Ovarian cancer is very rare in children. Symptoms in children might include abdominal pain, a lump in the belly, or abnormal bleeding. Any such symptoms should be checked by a doctor.

Symptoms in older adults

• Older adults may have similar symptoms, but changes in appetite, weight loss, and tummy discomfort can also be due to other age-related conditions. The CA125 test may be part of a check-up if ovarian cancer is suspected.

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.
• Liver disease or pancreatitis – these can sometimes affect CA125 levels.

Risk factors

• Age – ovarian cancer is more common in women over 50.
• Family history of ovarian or breast cancer (especially BRCA gene mutations).
• Personal history of breast, colorectal, or endometrial cancer.
• Endometriosis.
• Never having been pregnant, or having fertility issues.
• Obesity.
• Use of hormone replacement therapy (HRT) after menopause.

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.
• If you are receiving treatment for ovarian cancer, your doctor will arrange regular CA125 tests as part of your follow-up.

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)
• Genetic testing (if there is a family history of ovarian or breast cancer)

What to expect at your appointment

A healthcare professional will take a blood sample from your arm. You may be asked to have a full bladder for an ultrasound. The results usually come back within a few days. Your doctor will explain what the results mean and whether any further tests are needed. Be prepared to discuss your symptoms and medical history.

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.

When is surgery considered?

Surgery is often a key part of treatment for ovarian cancer. It may involve removing one or both ovaries, the fallopian tubes, the uterus, and sometimes nearby lymph nodes. For non-cancerous conditions like large cysts or endometriosis, surgery may also be recommended. Your doctor will explain the benefits and risks of surgery based on your specific situation.

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.

Mental health and emotional wellbeing

A cancer diagnosis or worrying about a high CA125 level can be emotionally challenging. You might feel anxious, sad, or stressed. These feelings are normal. Talk to your healthcare team about support services, including counselling or peer support groups. Your mental health matters just as much as your physical health.

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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