No GP wants to miss a diagnosis of ovarian cancer. A key challenge we face is working out when to test for ovarian cancer and which women to refer urgently to secondary care.
NICE guidance helps with this, recommending that GPs offer women with symptoms of possible ovarian cancer a CA125 blood test. If the CA125 result is over 35U/ml we refer our patients for ultrasound scans of their tummy and pelvis.
Interpreting CA125 can be a challenge, because GPs know that the level of CA125 in a patient’s blood can increase for a number or reasons, including non-cancerous conditions. Also, although CA125 has been studied extensively in screening clinical trials, until recently it had not been studied in primary care in symptomatic women.
What research did we undertake?
My team and I wanted to understand how accurate CA125 is at diagnosing ovarian cancer and whether the current threshold (35U/ml) was the best one to use in primary care.
We studied over 50,000 UK women who had a CA125 blood test in primary care and tracked them to see if they were diagnosed with ovarian cancer. We collected data on the women’s age, CA125 level and if they had an ovarian cancer diagnosis, to use in our analysis. We then used further data from more than 300,000 women in England to validate our findings.
What did our research results show?
Our research showed that CA125 is a useful test for detecting ovarian cancer in primary care, particularly in women who are 50 or over.
We also demonstrated for the first time that the current CA125 level of 35U/ml does not equally predict the risk of ovarian cancer among women of different ages. Using a single level of CA125 35U/ml in primary care can miss ovarian cancer in older women.
We also found that CA125 is less accurate in younger women, and using the current NICE recommendation of 35U/ml means that some women will have unnecessary, often invasive further investigation.
Based on our findings, we recommended that the CA125 level should be adjusted according to a woman’s age.
How will our research help GPs diagnose ovarian cancer?
Our research has informed the updates to NICE guideline (NG12) Suspected cancer: recognition and referral published on Thursday 26 March.
The update replaces the current single CA125 level of 35U/ml a with new age adjusted CA125 level for women aged above 40.
The guidelines also recommend no longer using CA125 in isolation in women age 39 or under, but to consider ultrasound as a first test.
What does our research mean for women with ovarian cancer symptoms?
We know that women with false negative CA125 results take on average twice as long to be diagnosed as those with an abnormal result.
The new CA125 thresholds for women age 40 and over could lead to more rapid diagnosis and treatment. They could also reduce harm caused to younger women age 39 years or under due to unnecessary referrals and invasive procedures triggered by false positive results.
Q&A with Dr Garth Funston
If you'd like to find out more about Dr Funston’s research, why not watch our Q&A.
- About Dr Garth Funston
Dr Garth Funston is a GP and Clinical Senior Lecturer in Primary Care Cancer Research at the Wolfson Institute of Population Health. His work spans multiple areas of cancer research, but he has a particular interest in early cancer detection. He has expertise in the analysis of large healthcare datasets, diagnostic test evaluation and the development and validation of diagnostic prediction models.
Garth currently sit on the Editorial Board of the British Journal of General Practice and the NICE Suspected Cancer Quality Standards Update Committee.
He undertook his clinical training at the University’s of St Andrews and Cambridge followed by clinical academic training posts (Academic Foundation Programme and NIHR Academic Clinical Fellowship) in Manchester. In 2021, Garth completed a Cancer Research UK funded PhD at the University of Cambridge, which focussed on the detection of ovarian cancer in primary care. He was lead author on the Royal College of General Practitioners Paper of the Year for Clinical Research (2021) and has been awarded the prestigious World Ovarian Cancer Coalition Transformational Research Prize.
