Ovarian cancer screening

Screening tests particular groups of people to find cancer early, when the chance of cure is highest. Before screening for any type of cancer can be carried out, doctors must have an accurate test to use. The test must be reliable in picking up cancers that are there. And it must not give false positive results in people who do not have cancer.

At the moment, there is no screening test reliable enough to use to look for ovarian cancer in the general population. But clinical trials are looking into screening tests for ovarian cancer that may be helpful for

• Women in general
• Women at high risk of cancer of the ovary

Until these trials publish their findings, we won't know whether the screening tests that are used work or not.

Two main tests have been tested in screening trials for ovarian cancer

• A blood test for CA125
• A transvaginal ultrasound

CA125 blood test

CA125 is known as a tumour marker for ovarian cancer. A tumour marker is a chemical given off by cancer cells that circulates in the bloodstream. Women with ovarian cancer tend to have higher levels of CA125 in their blood than women who do not have ovarian cancer. But there are some problems with this test that make it unsuitable for use as a screening test on its own

• Only about 85 out of every 100 women with ovarian cancer (85%)  have raised CA125
• Only 50 out of every 100 women with early stage ovarian cancer (50%) have raised CA125
• Women with other conditions can also have raised CA125

So you can see that if this test was used on its own, it would miss some cases of ovarian cancer. It would also pick out other women who did not have ovarian cancer. They would then need to have further tests, which could cause them anxiety and harm. We need to have another test that can reliably show who has ovarian cancer and who hasn't.

Researchers are looking for other possible tumour markers for cancer of the ovary. Doctors hope that by combining blood tests for markers they may be able to pick up more cancers and rule out people who don't have cancer more easily.

Transvaginal ultrasound

This is an ultrasound examination done by putting the ultrasound probe into the vagina. It gives a better picture of the ovaries than an ultrasound over the abdomen. Even so, it can still be difficult to tell whether there is a cancer on the ovary or just a harmless cyst.

A trial called UKCTOCS is looking at ovarian cancer screening in women in the general population between the ages of 50 to 74. The women who took part were selected at random from GP lists and then invited to join. This is so that the researchers get the most reliable results possible. This trial finished recruiting women in September 2005.

In this trial, both the CA125 blood test and the transvaginal ultrasound are being studied. There are 3 trial groups

• In group 1, women were given a yearly CA125 test and then, if that was abnormal, a transvaginal ultrasound scan
• In group 2, women were given a yearly transvaginal ultrasound and then, if that was abnormal, a CA125 blood test
• In group 3, the women were not given any screening tests

Group 3 are the control group. These women did not have either of the screening tests, but of course if any of them develop symptoms, they will see a doctor as normal. The researchers need to have a control group so that they can tell whether the screening tests pick up cancers earlier in the groups having the tests.

The first phase of the results were released in March 2009. 100,000 post menopausal women took part and the screening tests found 58 cancers, but missed the cancer in another 12 women. Half the cancers they found were at an early stage.

These early results suggest that the CA125 blood test and transvaginal ultrasound can be used on a large scale to successfully identify ovarian cancers. Over the next 5 years the researchers in the study will look at whether an ovarian screening programme using these tests could help to reduce deaths in the UK from ovarian cancer. So, it will be some time before we know whether a screening programme is helpful.

You may be able to have screening tests if you are thought to be at higher than average risk for ovarian cancer.  Screening is not yet available to everyone because the tests have not yet been proven to be reliable.  Researchers are still following the progress of the women who took part in the UKCTOCS ovarian cancer screening trial.  It will be some time before we have the results.

Higher than average risk means having 2 or more relatives on the same side of the family diagnosed with ovarian cancer or breast cancer at a young age. If your relatives were diagnosed before they were 50 years old, you may be able to have screening. But it is important to remember that these screening tests have not been fully tested yet. There is no guarantee that the tests will pick up every early ovarian cancer.

If you think you are at high risk of ovarian cancer, go to your GP. Your doctor can get in touch with your local genetics service (also called the family cancer clinic). You will be assessed and may be put on the UK Familial Ovarian Cancer Registry. At the genetics centre you'll be asked a series of questions about your family history. And you'll have counselling about your options, including the possible risks and benefits of screening.

If you are found to be at higher risk, you can be screened

• From 35 years old onwards or
• From 5 years before the age at which your youngest relative was diagnosed

Screening will then carry on yearly for the rest of your life.

The UK Familial Ovarian Cancer Screening Study (UK FOCSS) study is looking at screening women who are at a high risk of developing ovarian cancer because they have a family history of cancer of the ovary or breast, or they have family members with a known genetic fault (such as BRCA 1 or BRCA 2).

Results from the first part of this study have recently been published. The researchers think it may be better to do screening tests more often than once a year to pick up ovarian cancer at an early stage in women at increased risk. But they don’t know this for certain yet. The researchers are now following up women in the second part of the study who have screening every 4 months. They plan to publish these results in the future. There is more information about the results of the UK FOCSS study in our trials and research section.