Blood test an inaccurate way to detect the cancer: Expert

For years, women have turned up at cancer treatment clinics after sleepless nights thinking they have ovarian cancer, only for a battery of tests to tell them otherwise.

They have all had one thing in common - a high level of the protein CA-125 in their blood.

Many health screening packages offer a blood test that measures the level of the protein in the blood, with an elevated count considered a sign of ovarian cancer.

But this is an inaccurate way to detect the cancer and should not be used in this way, said Associate Professor Jeffrey Low, who heads the division of gynaecologic oncology at the National University Cancer Institute, Singapore.

Although a person with ovarian cancer could have a high level of CA-125, there are many other reasons for it, such as pregnancy and the presence of uterine fibroids or ovarian cysts. Both uterine fibroids and ovarian cysts are non-cancerous conditions.

Women who are ovulating or having their periods also have more of the protein in their blood.


"Every week, we have people who get referred to us after they have the CA-125 test and they come in telling us, 'Doctor, I have cancer,'" said Prof Low.

"In the weeks that they wait for an appointment, they can't sleep, they can't eat, they are worried and they think they are going to die."

Prof Low said these women have to go through the stress of additional blood tests and scans, and some even end up removing a healthy ovary in the worst- case scenario.

The effectiveness of the CA-125 test is, instead, in monitoring people who have already been diagnosed with ovarian cancer, he said.

If at the point of diagnosis the ovarian cancer patient is found to have a high level of CA-125, the blood test can be used to track the remission of the disease after treatment, which would be indicated by a drop in the level of the protein. An increase in CA-125, on the other hand, could mean the cancer has relapsed.

The blood test is also useful in helping doctors decide if an ovarian tumour is more likely to be malignant or benign.

There is still no good way to screen for ovarian cancer, but doctors say it is important for women to find out if they have a family history of the disease, which would put them at a higher risk of developing it.

These women should be more aware of the symptoms of the cancer, which include persistent abdominal bloating or swelling, pelvic pain, loss of appetite and breathlessness.

In the meantime, doctors discourage using the CA-125 test as an indication of ovarian cancer.

Samantha Boh

A version of this article appeared in the print edition of The Straits Times on October 19, 2016, with the headline 'Blood test an inaccurate way to detect the cancer: Expert'. Print Edition | Subscribe