Clinical usefulness and false-positive results of CA 125 as a tumor marker of ovarian cancer--a study on 674 patients.

To study the clinical usefulness and false-positive results of CA 125 as a tumor marker of ovarian cancer, we measured serum CA 125 levels in 197 patients with gynecological diseases, 274 normal, pregnant and postpartum women, 14 patients with abnormal pregnancy, 82 healthy women with a normal ovulatory menstrual cycle and 107 healthy non-pregnant subjects, using RIA kits. A level below 34 U/ml was considered the normal CA 125 range. The positive ratio of serum CA 125 in patients with malignant ovarian tumor was 81.3 per cent, and in those with serous cystadenocarcinoma the rate was 100 per cent. On the other hand, only one patient with benign ovarian tumor had a positive CA 125 value. Therefore, we suggest that CA 125 is useful for differentiation between benign ovarian tumor and ovarian cancer. However, because the positive ratio of CA 125 level is high in patients with recurrences of uterine cervical adenocarcinoma, those with tubal cancer, endometriosis, early pregnancy, abnormal pregnancy plus intrauterine fetal death and menstruating women, such situations must be given due attention when CA 125 is used as a tumor marker of ovarian cancer.