Clinical evaluation of serum sialosyl-Tn antigen levels in comparison with CA 125 levels in gynecologic cancers

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Abstract
The serum levels of sialosyl‐α2,6GalNAcαl‐0‐serine/threonine (S‐Tn) antigen and CA 125 antigen were measured in 205 patients with gynecologic tumors, including 48 ovarian cancers, 20 endometrial cancers, 29 cervical cancers, 57 benign ovarian tumors, 37 uterine leiomyomas, and 14 adenomyosis. Using a cutoff value of 41 U/ ml for S‐Tn and 35 U/ml for CA 125, positive findings were obtained in ovarian cancers in 31 of 48 (64.6%) patients with S‐Tn antigen, and in 36 of 48 (75%) patients with CA 125. In uterine malignancies, positive findings were obtained in 11 of 49 (22.4%) patients and in 8 of 49 (16.3%) patients with the serum S‐Tn and CA 125 antigens, respectively. In ovarian benign tumors, false‐positive findings with CA 125 were observed in 16 of 57 (28.1%) patients, but with S‐Tn antigen in only 3 of 57 (5.3%) patients (P < 0.03). For the ovarian tumors, excluding patients with recurrent disease, the specificity, positive predictive value, and accuracy of the serum S‐Tn antigen level for detecting cancer exceeded that of the serum CA 125. The combined assay of serum S‐Tn and CA 125 antigens gave positive results in 38 of 48 (79.2%) patients with ovarian cancers; most of the negative findings were obtained in Stage I disease. A significant decreases in serum S‐Tn level was observed after cytoreductive surgery in 14 patients with ovarian cancer (P < 0.01). Four patients with a subsequent recurrence showed a concomitant rise in serum S‐Tn. The cyst fluid and ascitic fluid showed high levels of S‐Tn antigen in patients with ovarian cancer, in contrast to findings in patients with benign ovarian tumors. In conclusion, serum S‐Tn antigen has limited use in diagnosing early stage ovarian cancer and uterine malignancies, but it can detect with accuracy ovarian cancers when used in a combination assay with CA 125 and can monitor the status of disease after therapy.