Evidence of Benefit
Rationale for Screening
The rationale for screening for hepatocellular carcinoma (HCC) is based on the concept that populations at high risk for HCC, such as those with cirrhosis, can be identified. However, 20% to 50% of patients presenting with HCC have previously undiagnosed cirrhosis.[1,2] These patients would not be recruited into a surveillance program if the presence of cirrhosis is used to define a target population. The modalities potentially available for screening include serum alpha-fetoprotein (AFP) and ultrasonography. Abnormal screening results may lead to liver biopsy for diagnosis. Complications of liver biopsy are reported in 0.06% to 0.32% of patients, and typically occur within the first few hours after the biopsy.Tumor Markers for the Detection of Hepatocellular Carcinoma
There are four categories of tumor markers that are currently being used or studied for the detection of hepatocellular carcinoma. These include oncofetal antigens and glycoprotein antigens; enzymes and isoenzymes; genes; and cytokines.Alpha-fetoprotein
Serum AFP, a fetal-specific glycoprotein antigen, is the most widely used tumor marker for detecting patients with HCC. The reported sensitivity of AFP for detecting HCC varies widely in both hepatitis B virus (HBV)-positive and HBV-negative populations, which is attributable to overlap between screening and diagnosis study designs. When AFP is used for screening of high-risk populations, a sensitivity of 39% to 97%, specificity of 76% to 95%, and a positive predictive value (PPV) of 9% to 32% have been reported.[5-9] AFP is not specific for HCC. Titers also rise in acute or chronic hepatitis, in pregnancy, and in the presence of germ cell tumors.
A prospective, 16-year, population-based, observational study of screening for hepatocellular cancer among 1,487 Alaska Natives chronically infected with HBV compared survival among screen-detected HCC patients with a historical comparison group of clinically diagnosed HCC patients. The screening program’s target was AFP determination every 6 months. It achieved 97% sensitivity and 95% specificity (excluding pregnant women) for HCC. Such high sensitivity and specificity have not been found for other high-risk groups, such as individuals with cirrhosis.[11,12] Whether screening actually improved survival is not clear.Hepatic Ultrasound
Limitations in the sensitivity and specificity of AFP in surveillance of high-risk populations led to the use of ultrasound as an additional method for detection of HCC. Studies in both healthy hepatitis B surface antigen carriers  and in patients with cirrhosis  have defined the performance characteristics of ultrasound as a screening test for HCC. Sensitivity in the former was 71% and in the latter 78%, with 93% specificity. The PPVs were 14% and 73%, respectively. In a study of patients who were on a waiting list for liver transplantation, ultrasonography was found to have a sensitivity of 58%, a specificity of 94%, a negative predictive value of 91%, and a PPV of 68%.Computed Tomography
Limitations in the sensitivity and specificity of AFP and ultrasound in surveillance of high-risk populations, such as individuals with cirrhosis, led to the assessment of computed tomography (CT) as an additional method for detection of HCC. Studies in patients with cirrhosis suggest that CT may be a more sensitive test for HCC than ultrasound or AFP more than 20 μg/L.[11,12]Efficacy of Screening and Surveillance Programs
A controlled trial of 18,816 persons aged 35 to 59 years with hepatitis B in Shanghai randomly assigned patients to a screening group using AFP and ultrasound every 6 months versus a usual-care group. HCC mortality was lower in the screened group (83.2 vs. 131.5 per 100,000; mortality rate ratio of 0.63 [95% confidence interval (CI), 0.41–0.98]). While these results are promising, there were problems, including the following:
- The results varied in different publications.
- The comparison group was not actively followed.
- The CI was near 1.0.
- Intention-to-treat analysis was not used.
- Assessment of outcome was not blinded.
- Generalizability to other populations is uncertain.
A randomized controlled trial studied 5,581 men aged 30 to 69 years who were chronic carriers of HBV between 1989 and 1995 in Qidong County, China. Of these men, 3,712 were randomly assigned to a screening group and 1,869 to a control group. Screening entailed 6-monthly AFP assays, with follow-up of patients having an abnormal (≥20 μg/L) test result. All patients were followed up for liver cancer and/or death. The overall sensitivity and specificity of the program were 55.3% and 86.5%, respectively. In patients who complied with all scheduled screening tests, sensitivity was 80% and specificity was 80.9%. The mortality rate in the screening group (1,138 per 100,000 person-years) was not significantly different from that in the control group (1,114 per 100,000 person-years), although AFP screening resulted in an earlier diagnosis of liver cancer (i.e., percentage of cases in stage I was significantly higher in the screened group [29.0%] than in the control group [6%]). A review concluded that the method of measuring AFP was not sensitive enough to detect HCC, affecting interpretation of the negative result of this trial.References
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