Significance of measurement of a carbohydrate antigenic determinant 19-9 (CA 19-9) for monitoring colorectal cancer patients.

The significance of measurement of serum CA 19-9 levels and the correlation between the serum levels of CA 19-9 and CEA in 61 patients with colorectal cancer were investigated. CA 19-9 levels above 37 U/ml were found in 24.6 per cent, while CEA levels above 5 ng/ml were observed in 34.4 per cent. Elevation of one or both of two antigens was found in 44.3 per cent. In patients with elevated CA 19-9 levels, the CA 19-9 levels returned to normal after curative resections, whereas patients with normal levels of this antigen showed only slight or no differences after curative resections. Measurements of this antigen were useful for the evaluation of the effect of surgery, especially in patients with normal CEA levels and elevated CA 19-9 levels. Combination assays of these antigens may be more useful than CEA alone for monitoring colorectal cancer patients.