CA125 expression at clinical diagnosis by ovarian carcinoma not detected through antecedent serum CA125 screening

At the time of clinical presentation with ovarian carcinoma, 85% of women have an elevated serum level of the CA125 antigen, but the duration of the preclinical phase of expression of CA125 is unknown. From the database of The Royal London Hospital ovarian cancer screening project, 19 women were identified who had a serum CA125 level <30 IU ml⁻¹, measured between 2 and 24 months prior to their clinical diagnosis of ovarian cancer. Histological sections of tumor removed from these women were reviewed. In 17 cases tumor tissue was immunocytochemically stained for CA125 expression. Tumor blocks of 40 women presenting clinically with ovarian cancer with known preoperative CA125 levels were also stained for CA125 expression. The serum CA125 level at the time of diagnosis was available in six of the 19 screening study cases, four of which had levels> 30 IU ml⁻¹. In five of the 13 cases with unknown serum CA125 levels, ovarian tumor tissue expressed CA125. Among the 40 controls, 24 tumors expressed CA125 and all 24 had a serum level greater than 47 IU ml⁻¹. An annual screening test using serum levels of CA125 at a cut-off of 30 IU ml⁻¹, cannot detect all cases of ovarian cancer that express the antigen at the time of clinical diagnosis. The development of a panel of complementary tumor markers will be necessary to provide a test with a higher sensitivity for the detection of preclinical ovarian cancer.