Encouraging results for ovarian cancer screening test
A new two-stage process could be a way of spotting women who are at high risk of ovarian cancer early, and reassuring other women that their risk of ovarian cancer is low.
BMJ Group News
What do we know already?
Ovarian cancer is a cancer that starts in one, or both, of a woman’s ovaries. Every year about 6,700 women in the UK are diagnosed with ovarian cancer, making it the fifth most common cancer among women in the UK.
Ideally, a good screening test would accurately spot ovarian cancers early, avoid unneeded treatments, and give women a better chance of being cured from treatment. At the moment there isn’t a good screening test to find this cancer before it causes symptoms.
In this study, researchers used a two-stage screening test to spot women at high risk of ovarian cancer. In the first stage, more than 4,000 women aged between 50 and 74 were given an annual blood test for a protein called CA125. Women with ovarian cancer tend to have high levels of CA125 in their blood, but on its own this isn’t an accurate test for ovarian cancer.
In the second stage, researchers used a computer program to analyse the women’s CA125 test results, and look for unusual or unexpected changes in a woman’s CA125 levels compared to previous blood test results. The researchers then divided the women into three groups.
One group of women (in the low risk group) were called back for repeat tests every year. Women in the second group (the intermediate risk group) were called back three months later. A third group was seen straight away by a specialist doctor and given a test called a transvaginal ultrasound, to try and spot early signs of ovarian cancer.
The researchers then looked to see whether the screening tests accurately predicted women’s ovarian cancer risk. The study lasted about 11 years.
What does the new study say?
Overall, about 83 in every 100 women screened were in the low risk group, about 14 in every 100 were in the intermediate risk group, and about 3 in every 100 were in the high risk group. Four women were diagnosed with early-stage ovarian cancer.
The researchers then looked at how accurate these results were. The screening test correctly identified women who didn’t have ovarian cancer 99 percent of the time.
When looking at the women who had surgery to find out how often the test correctly predicted their risk, the researchers found the test was right 40 percent of the time. This is much higher than the level of 10 percent that doctors generally say makes a test useful.
How reliable is the research?
Some of the results of this study are very encouraging, and it’s important that these screening tests are able to accurately spot people who are well and who don’t need treatment. This is called a test’s specificity. But it’s also important to know how good this test is at correctly identifying people who have ovarian cancer. This study didn’t look at this aspect of the test’s accuracy (called sensitivity). Without also knowing how sensitive the test is we can’t be sure if it’s a reliable and useful screening test. The researchers say there needs to be a much larger study to find this out.