What role do CA-125 levels play in the diagnosis and management of suspected ovarian cancer?

Role of CA-125 in diagnosis: Serum CA125 measurement is recommended in primary care for women presenting with symptoms suggestive of ovarian cancer, especially those aged 50 or over. A CA125 level of 35 IU/ml or greater prompts an urgent ultrasound scan of the abdomen and pelvis to further evaluate for ovarian cancer. If the ultrasound suggests ovarian cancer, the woman should be referred urgently via a suspected cancer pathway for specialist assessment. If CA125 is below 35 IU/ml or if CA125 is elevated but the ultrasound is normal, other causes should be considered, and the woman should be advised to return if symptoms persist or worsen ¹,²,³,⁴.

Role of CA-125 in secondary care and management: In secondary care, CA125 should be measured if not already done. It is used alongside imaging and clinical assessment to guide further investigations. CA125 is part of the calculation of the Risk of Malignancy Index (RMI), which helps stratify risk and determine referral to specialist multidisciplinary teams. A high RMI (≥250) indicates the need for specialist referral. CA125 levels also assist in monitoring disease extent and response to treatment but tissue diagnosis remains essential before chemotherapy, except in exceptional cases ¹.