CA 125 Serum Levels Correlated With Second-Look Operations Among Ovarian Cancer Patients

Abstract

CA 125, which is an antigenic determinant expressed by many epithelial ovarian cancers, is measured in serum using a solid phase immunoradiometric assay. Sera from 55 patients who were in clinical remission and underwent a second-look operation to assess disease status after chemotherapy were studied prospectively. All patients had the CA 125 assay performed within one week before their second-look operation. Twenty-four patients (44%) had no histologic or cytologic evidence of disease, seven patients (13%) had microscopic disease, 13 patients (24%) had diseae measuring 1 mm to 1.5 cm, and ten patients (18%) had disease greater than or equal to 1.5 cm in maximum tumor dimension. None of the 24 patients with a negative second-look operation had a positive CA 125 antigen level (greater than or equal to 35 U/mL), compared with six of 20 patients (30%) with less than 1.5 cm disease, and six of ten (60%) with greater than or equal to 1.5 cm disease (P < .0001). All 12 patients with an elevated CA 125 antigen level (greater than or equal to 35 U/mL) had disease discovered at their second-look operation. Thus, in this setting the predictive value of a positive CA 125 titer (greater than or equal to 35 U/mL) was 100%. The predictive value of a negative CA 125 antigen level (less than 35 U/mL) was 56%, i.e., the test did not exclude the presence of disease in 44% of patients with a positive second look. the maximum tumor size associated with at least one prior negative antigen level was 1.9 cm. Therefore these data suggest that a second-look laparotomy cannot be obviated in patients with a negative CA 125 antigen level. The CA 125 assay may prove valuable in predicting the presence of subclinical disease in those patients whose antigen levels are elevated (greater than or equal to 35 U/mL) and who are in clinical remission.