Regular monitoring and an early diagnosis of childhood tumors can improve the clinical course and treatment response, which ultimately improves long-term outcomes (18). The blood tumor markers that are described in this study can be considered good indicators and can provide an acceptable diagnostic accuracy and are convenient and cost-effective.
The results of this study showed that hepatic tumor patients had significantly higher serum levels of PIVKA-II and AFP than extrahepatic abdominal tumor patients.
Prothrombin glutamate carboxylation in the liver gives rise to normal prothrombin, which contains 10-carboxylic glutamate residues. The process depends on the presence of vitamin K. In pathological states when vitamin K is too low or in the presence of a vitamin K-dependent antagonist of carboxylase, the insufficient carboxylation of glutamic acid results in the production of PIVKA-II(19).
Motohara K. et al. reported that vitamin K treatment in two hepatoblastoma patients resulted in only a moderate reduction in PIVKA-II levels. An immunohistochemical study of liver tissue showed the presence of PIVKA-II in hepatoblastoma cells (8). Maha F. et al. reported similar outcomes; after vitamin K administration, PIVKA-II levels decreased in both the chronic hepatitis group (P = 0.022) and the cirrhosis group (P = 0.024) but not in the HCC group (P = 0.187) (20). These findings suggested that the elevation of PIVKA-II in patients with liver tumors was not due to deficiency in the nutrient vitamin K but due to the overproduction of PIVKA-II in tumor cells.
The subgroup analysis showed that PIVKA-II and AFP levels in patients with malignant hepatoblastoma were higher than those in patients with the benign tumor, hemangioendothelioma, in our study.
Imamura et al. reported that serum PIVKA-II levels were significantly elevated in patients with more aggressive tumor characteristics (21). Recently, many studies have demonstrated that elevated serum PIVKA-II is related to larger tumor size, more frequent vascular invasion, more intrahepatic metastasis, and recurrence after treatment(22).
A couple of previous studies reported that the optimal cutoff value of serum PIVKA-II for HCC diagnosis was estimated to range from 30 to 42 mAU/ml(23). The ROC curve analysis showed that the optimal cutoff value of PIVKA-II for the diagnosis of childhood hepatic tumors was 32.6 mAU/ml and that for differentiating hepatoblastoma from hemangioendothelioma was 47.1 mAU/ml. The cutoff values of serum PIVKA-II for the diagnosis of hepatic tumors in children and adults were similar and were not affected by age.
In previous studies, the sensitivity of PIVKA-II in the diagnosis of HCC was 51.0%-77%, the specificity was 67.8%-91.2%, and the AUROC was 0.701–0.854, all of which were higher than the sensitivity, specificity, and the AUROC of AFP (16, 24). In our study, the sensitivity, specificity and AUROC of PIVKA-II in the diagnosis of childhood hepatic tumors and in the differentiation of hepatoblastoma from benign hepatic tumors were all higher than AFP. PIVKA-II is a good marker with good sensitivity and specificity in the diagnosis of hepatic tumors in both children and adults.
Serum PIVKAII and AFP are produced through different mechanisms. AFP secretion in HCC results from a re-expression of a fetal antigen in the tumor, and PIVKA-II results from an independently acquired posttranslational defect in protein processing(25). Therefore, the two markers are independent from each other in the diagnosis of hepatic tumors(26). A few studies reported that PIVKA-II combined with AFP had great advantages as a biomarker for HCC screening(27, 28). The maximum AUROC was 0.846, which was higher than that of PIVKA-II or AFP alone(29). We further evaluated the diagnostic performance of the combination of the two markers. The results showed that the combination of PIVKA-II and AFP further increase the efficiency for the diagnosis of childhood hepatic tumors (AUROC = 0.891) and for the differentiation of hepatoblastoma from benign hepatic tumors (AUROC = 0.895). Our study was broadly consistent with these findings.