Clinical significance of alpha-fetoprotein mRNA in blood of patients with hepatocellular carcinoma

Abstract

Background: Alpha-fetoprotein (AFP) messenger RNA (mRNA) in the blood reflects the presence of circulating hepatocellular carcinoma (HCC) cells and is a sensitive marker of HCC extrahepatic metastases. The specificity of this molecular marker and its correlation with the main HCC clinical–pathological parameters remains controversial, however. Methods: AFPmRNA was determined in 50 HCC patients and in 50 patients with diagnosis of cirrhosis (6), or colon (24) or, pancreatic (20) carcinoma. HCC patients with clinically evident extrahepatic metastasis were excluded. HCC diagnosis was confirmed in all patients by histology on percutaneous biopsies or surgical specimens; pathological grading was assessed at the same time. Results: AFPmRNA was positive in 20 HCC patients (40%) and in 18 patients without HCC (36%). The presence of AFPmRNA in the blood correlated significantly with cholestatic indices (p<0.01), nodule size (p=0.03), vascular invasion (p=0.006) and moderately or poorly differentiated HCC (p<0.0001). Moreover, survival analysis showed a significant impact of AFPmRNA detection on overall (p=0.04) and recurrence-free survival (p=0.0007) after a median follow-up of 17 months. Conclusions: Although AFPmRNA is frequently detected in the blood, even in benign liver diseases or gastroenteric tumors, in HCC patients without clinical evidence of extrahepatic metastases it seemed to identify the biologically more aggressive tumors.

Introduction

Each year, almost one million people die of hepatocellular carcinoma (HCC) worldwide [1] and recent studies have shown that the incidence of hepatocellular carcinoma (HCC) is increasing in the West [2]. Treatment decisions and prognostic predictions in patients with HCC are commonly based on macroscopic tumor characteristics, detected by imaging studies (tumor size, number, lobar distribution, vascular invasion and extrahepatic metastasis) and by the function quality of the nonmalignant liver. Although advances in patients selection and treatment have improved survival rates of HCC patients [3], intrahepatic and/or extrahepatic recurrences are still frequent after potentially curative therapies such as liver transplantation (OLT), resection or percutaneous treatments [3], [4], [5].

As in other solid cancers [6], the haematogenous spread of HCC cells has been suggested as an important mechanism in HCC progression, both inside and outside the liver. According to this theory, the detection of HCC cells in the blood may be a good indicator of greater tumor invasiveness. In fact, the particular vascular architecture of HCC nodules might explain the easy release of tumor cells into the sinusoids, and consequently into the portal or hepatic veins, favouring both intra- and extrahepatic dissemination. In the past decade [7], alpha-fetoprotein (AFP) messenger RNA (mRNA) detected by reverse-transcription polymerase chain reaction (RT-PCR) has been proposed as a sensitive marker of HCC cells disseminated in the bloodstream. Clinical studies have suggested that AFPmRNA in the peripheral blood is strongly associated with the presence of extrahepatic HCC metastasis [7], [8], [9], that it has prognostic value in patients treated with percutaneous ethanol injection (PEI) and/or transarterial chemoembolization (TACE) [10] and that it is potentially able to predict postsurgical HCC recurrence [11], [12]. Some studies [7], [13], however, have reported AFPmRNA positivity in healthy blood donors and in those with liver metastases or other benign liver diseases, casting doubts on the specificity of this method. Moreover, it is not clear whether specific liver function alterations can influence AFPmRNA detection in the blood and the particular relationship between this genetic marker and the macroscopic tumor characteristics commonly used for therapeutic decision [14].

Hence, this prospective study on AFPmRNA specificity, for which a large group of consecutive patients with HCC, nonmalignant liver cirrhosis, or pancreatic and colon cancers was enrolled. In the HCC patients, AFPmRNA was correlated both with the main clinical–pathological features of the tumor and with liver function tests results in order to identify the relative influence of HCC invasiveness and of liver impairment on AFPmRNA molecular detection in the blood. In addition, overall and recurrence-free survival analysis was performed in order to study the AFPmRNA prognostic significance in HCC patients.