Ovarian cancer is the sixth most common cancer in women in the UK, with about 7,400 new cases every year. This number equates to approximately 20 diagnoses a day.

Early diagnosis is key to successfully treating cancer, and ovarian cancer is no exception. But as seen frequently with many different cancer types, there are a number of obstacles we need to tackle for early diagnosis to become a reality.

The answer for ovarian cancer could involve a blood test.

We often hear about blood tests when it comes to detecting cancer. And while many are still in the early phases of development, cancer blood tests do exist, and some are even currently being used in GP practices.

A team of researchers, based at the Universities of Cambridge, Manchester and Exeter and funded by Cancer Research UK and NIHR, have been investigating a blood test for ovarian cancer – CA125 – that’s already out there. Their research, published this week in PLOS Medicine, found it is far more predictive than we originally thought and could potentially pick up other forms of cancer.

The importance of early diagnosis

Like many other cancers, survival of ovarian cancer depends on the stage at which the cancer has been diagnosed.

Put simply – the earlier the better.

The differences in survival between an early stage and late stage diagnosis are significant. 93% of people diagnosed with ovarian cancer diagnosed at the earliest stage (stage 1) survive their disease for 5 years or more, compared to just 13% of those diagnosed at the latest stage (stage 4).

Sadly, ovarian cancer is often diagnosed late. The majority of women will be diagnosed when they notice symptoms, typically when they visit the GP. And while symptoms can occur at every stage of the disease, the symptoms are non-specific, such as abdominal pain and bloating, and can be hard to pinpoint.

Why investigate a test that we already have?

The CA125 test is a blood test used around the world, including in the UK, to help identify ovarian cancer in women who are already presenting with symptoms. Those who have above a certain level of CA125 in their blood are advised to follow on with further tests, such as an ultrasound.

How does the CA125 test work?

  • CA125 is a protein often found on the surface of ovarian cancer cells and in some normal tissues. Women with ovarian cancer often have a high level of this protein in their blood.
  • A high level of CA125 in your blood could be a sign of ovarian cancer. It can also be a result of other conditions such as endometriosis, fibroids and even pregnancy.
  • If a test shows you have high levels of CA125, you may be referred for a scan to check for possible causes.

Back in 2011, the National Institute for Health and Care Excellence (NICE) recommended that women with symptoms of possible ovarian cancer be tested for CA125 in a primary care setting, typically at your GP surgery.

While the CA125 test has been studied in women in secondary care, for example, women with pelvic masses in a hospital setting, the test hadn’t been evaluated for women who had seen their GP with symptoms that could be ovarian cancer.

The research team, working as part of the CanTest collaborative, set to fill in this missing data.

“There’s around 7,000 women diagnosed with ovarian cancer in the UK each year. Picking up the disease early is really important because we’re more likely to be able to treat and cure the disease effectively if we do that…..”

“The CA125 blood test has been around and available to GPs for a while. But it’s never actually been evaluated in primary care,” explains Dr Garth Funston, from the University of Cambridge, who led the study.

“Tests perform differently depending on how you use them and who you use them in. So to really understand how this test performs, we needed to study it in the population in which it was used.”

Funston says that before this study, doctors relied on evidence and results from research conducted in other settings. “This study shows that it is a really useful test in helping to work out who to refer on for further investigation.”

The results are in

The study looked at 50,000 women who had seen their GP and took the CA125 test between 2011 and 2014.

This research found that 10% of women with higher levels of the protein biomarker were diagnosed with ovarian cancer, making an abnormal test 12 times more predictive than previous estimates had suggested.

What’s more, this study showed for the first time that an abnormal CA125 result in primary care was not only associated with ovarian cancer – over 350 women with high protein levels had the disease – it also found more than 380 women with an abnormal CA125 result had another type of cancer such as pancreatic, lung or bowel cancer. These results reflect how important it is that GPs remain alert to the risk of other cancer types when carrying out specific triage tests.

Age was a big factor that affected the results. The proportion of women with an abnormal test who had any cancer, was much higher in women aged 50 or over (33%) compared to women younger than 50 (6%).

“One of the most exciting things from this research is that we’ve been able to develop models which give the individualised risk or probability of a woman having cancer, based on their CA125 test level and their age,” Funston comments.

“We think this will be really useful in helping women and GPs make decisions about the need for further testing and referral,” he adds.

This research demonstrates a readily available and tangible test that can be used more often by GPs to give people more time with their loved ones.

Significant investment in diagnostic equipment and technology, along with NHS staff is urgently needed to diagnose more cancers at an earlier stage and save lives. Through the right investments and policies, the UK has the potential to become a world leader in the early detection and diagnosis of cancer.

Dr Jodie Moffat, Cancer Research UK’s head of early diagnosis.

What does this mean for patients?

The team at Cambridge hope that this new, added insight on the performance of the CA125 test will help aid the diagnosis pathway for ovarian cancer.

Fiona Barve is a science teacher who lives near Cambridge. She was diagnosed with ovarian cancer in 2017 after visiting her doctor with stomach pains.

“I hadn’t heard of the CA125 blood test before my GP suggested that I take one. Although I was diagnosed at a late stage, the test helped identify the problem – I didn’t even know this test existed before. I’d like to see a day when tests like this are routinely used to help more people have their cancer diagnosed early,” she says. “I was fortunate my surgery, which I received within four weeks of being diagnosed and chemotherapy worked for me. Now I feel lucky to be around.”

Fiona has been cancer free since April 2019 and leads a fit and active life, working as a science teacher at her local school three days a week. She is monitored every 3 months by her consultant Professor James Brenton, a process which includes having regular CA125 tests.

Although the CA125 test is already being used in GP surgeries, this new data provides a great opportunity to encourage the use of the CA125 test as an effective triage tool.

“It would be fantastic to see the models we’ve developed integrated into the GP practice to help guide decisions about which patients need to be referred urgently for further investigation and which patients can be reassured. So I’d really like to see the models implemented and used,” Funston concludes.

Lilly