COMPARISON OF CA-125 ASSAYS WITH ABDOMINOPELVIC COMPUTED TOMOGRAPHY AND TRANSVAGINAL ULTRASOUND IN MONITORING OF OVARIAN CANCER

Objective: To compare serum CA 125 assays with computed tomography (CT) and transvaginal ultrasound (TVUS) for early detection of disease recurrence in patients with ovarian cancer. Methods: Sixty-two patients with nonmucinous epithelial ovarian cancer who had positive CA 125 levels (> 35 U/ml) were studied. We performed a retrospective review to determine the usefulness of serum CA 125 measurements. Setting the cut-off limit at either 35 U/ml or 16 U/ml, the accuracy of CA 125 measurements was compared with that of CT scanning, TVUS and operative findings at second-look laparotomy (SLL) in the early detection of recurrent tumors. Results: Compared with SLL, both the specificity and the positive predictive value of CA 125 measurements were 100% at 16 and 35 U/ml. The sensitivity and the negative predictive value were 30.8 and 71.9%, respectively, below 35 U/ml and 53.8 and 79.3%, respectively, below 16 U/ml. The false-negative rate of CT was 36.1%. When the cut-off limit was reduced from 35 to 16 U/ml, 57.1% of patients considered to be in remission were reclassified as having persistent disease. A complete response confirmed by CT did not represent remission: CA 125 levels were 7.5-fold higher at the time of re-evaluation by CT. TVUS also lagged behind CA 125 assays in detecting disease recurrence. The sensitivity of ultrasound appeared to be lower than that of CT because it failed to detect extrapelvic lesions. Conclusion: A screening threshold (cut-off level) of 16 U/ml for CA 125 should be used to detect recurrent serous ovarian adenocarcinoma. Although ultrasound is a convenient method of detecting intrapelvic lesions, and has cost benefits, CT is necessary to detect extrapelvic recurrence. Neither CT nor ultrasound are more accurate than serial CA 125 assays in detecting disease recurrence.