CA125 in ovarian cancer screening
Q - A patient with long-standing abdominal pain has been given a diagnosis of ovarian cancer. Is there any role for CA125 as a screening test?
A - Although often referred to as 'the silent killer', recent publications have indicated 95 per cent of women with ovarian cancer suffer vague symptoms prior to diagnosis. The most common symptoms were abdominal bloating and pain, gastrointestinal, urinary and constitutional.
Many women felt a failure to recognise such symptoms could be caused by ovarian cancer resulted in a delay in diagnosis. But the great majority with these symptoms will not have ovarian cancer and it would therefore be inappropriate to refer them all for investigation.
Using CA125 alone, as a screening test, in a primary care setting is not the answer. Sensitivity and specificity are poor, with 50 per cent of women with early-stage disease having normal values and only about 1 per cent of women with a raised value having ovarian cancer.
CA125 levels can be elevated by a wide range of pathological conditions, both benign and malignant, as well as by physiological variations.
Improvements in the sensitivity and specificity of CA125 can be achieved by assessing changes in values over time, as opposed to absolute values, but this involves using a complicated algorithm. Interpretation of results is difficult so its use a screening test in primary care cannot be recommended.
As well as the nationwide UKCTOCS trial for asymptomatic women, a further randomised controlled trial for symptomatic women is recruiting at Bart's. GPs have the opportunity to refer patients with vague symptoms for an ovarian cancer screen using both ultrasound and CA125.
Until we have results, participating GPs should consider ovarian cancer when women, particularly those over 45, present with vague symptoms.
A pelvic examination is appropriate and an ultrasound or referral may be needed.
Mr Barnaby Rufford,
clinical research fellow,
Gynaecology Oncology Unit,
St Bartholemew's Hospital, London