Use of serum tumor markers in the differential diagnosis between ovarian and colorectal adenocarcinomas.

In the search for a method to facilitate the preoperative discrimination of ovarian carcinomas from colorectal carcinomas serum levels of 6 tumor markers were measured in 47 patients presenting with ovarian cancer and compared to levels found in 24 female patients with advanced, untreated colorectal cancer. The markers studied were CA 125, CA 15.3, CA 19.9, CEA and two recently developed mucin markers, CA M29 and CA M26. Levels of CA 125, CA 15.3, CEA and CA M29 showed significant differences between both groups. In predicting ovarian cancer, sensitivity was highest for CA 125 at 94% (35 U/ml cutoff level). However, the specificity of CA 125 was at 71% low. Specificity increased significantly by using a combination of a CA 125-positive score (greater than 35 U/ml) and a simultaneous negative CEA score (less than or equal to 5 ng/ml) (specificity 100%, sensitivity 81%). A CA 125/CEA serum ratio greater than 25 resulted in the highest discriminative power with a specificity of 100% and a sensitivity of 91% resulting in an overall test accuracy of 94%. It is concluded that the serum tumor markers used, especially a combination of CA 125 and CEA, are helpful in the preoperative differential diagnosis between adenocarcinomas of ovarian and colorectal origin.