Assessment of KL-6 as a tumor marker in patients with hepatocellular carcinoma

To investigate the clinical significance of KL-6 as a tumor marker of HCC in two different ethnic groups with chronic liver disease consecutively encountered at outpatient clinics.

Serum KL-6 was measured by the sandwich enzyme immunoassay method using the KL-6 antibody (Ab) as both the capture and tracer Ab according to the manufacturer's instructions (Eisai, Tokyo, Japan). Assessment of alpha fetoprotein (AFP) and protein induced vitamin K deficiency or absence (PIVKA-II) was performed in both groups using commercially available kits.

A significantly higher mean serum KL-6 (556+/-467 U/L) was found in HCC in comparison with non-HCC groups either with (391+/-176 U/L; P<0.001) or without (361+/-161 U/L; P<0.001) liver cirrhosis (LC). Serum KL-6 level did not correlate with either AFP or PIVKA-II serU/Levels. Using receiver operating curve analysis for KL-6 as a predictor for HCC showed that the area under the curve was 0.574 (95%CI = 0.50-0.64) and the KL-6 level that gave the best sensitivity (61%) was found to be 334 U/L but according to the manufacturer's instructions; a cut-off point of 500 U/L was used that showed the highest specificity (80%) in comparison with AFP and PIVKA-II (78% vs 72% respectively). Combining the values of the three markers improved specificity of AFP for HCC diagnosis from 78% for AFP alone; 93% for AFP plus PIVKA-II to 99% for both plus KL-6 value (P<0.001). Mean serum alkaline phosphatase level was significantly higher in KL-6 positive (564+/-475) in comparison with KL-6 negative (505+/-469) HCC patients (P = 0.021), but such a difference was not found among non-HCC corresponding groups.

KL-6 is suggested as a tumor for HCC. Its positivity may reflect HCC-associated cholestasis and/or local tumor invasion.