In the largest study of biomarkers for the diagnosis of early stage HCC, we showed that AFP had a sensitivity of 66% and specificity of 81%, at a new cutoff of 10.9 ng/mL. AFP had the best AUC in tumors at the BCLC stage 0 and BCLC state A when compared to other markers. Importantly, AFP had the best performance of all the markers for BCLC stage 0 HCC, the detection of which is the main goal of a surveillance program.
AFP has been the most widely utilized serologic test for HCC. A previous case control study involving 170 patients with HCC, only 68 with early HCC, and 170 matched cirrhosis controls showed that the cutoff of 20 ng/mL maximizes the sensitivity and specificity (23
). However, the sensitivity of AFP at this cutoff has ranged from 41–65% with specificity from 80–94% in multiple prior studies performed (24
). Our study eliminated a large portion of the pitfalls and limitations from previous studies. Our study accounted for verification bias, as we utilized histology and imaging as diagnosis of HCC based on the latest definition of HCC and AFP was not used as the definition of a case, there was appropriate blinding of operator when assays were performed, appropriate controls were used with 6 month post-enrollment follow up to eliminate false negatives, and an appropriately powered multicenter study design. The goal of a surveillance program is the detection of early stage tumor, in particular very early stage tumor, where it allows curative intervention to improve outcomes, and our study shows that AFP has the best performance in those with BCLC stage 0 and BCLC stage A.
Our current study shows that the performance of DCP, but not that of AFP, is significantly affected by the etiology of liver disease for the diagnosis of early stage HCC. For the diagnosis of early stage HCC, AFP-L3 is not useful and not recommended likely due to the need for an elevated total AFP thereby, limiting its effectiveness. The sensitivity of DCP in patients with viral etiology is 79% for early stage HCC, whereas the combination of AFP and DCP in viral etiology was not better than each of the serum markers alone (). For non-viral etiology AFP performed better than the other markers alone and adding other markers to it improved little. DCP appears to perform better in those with viral etiology but the combination of AFP and DCP did not improve the overall performance.
Our study determined a lower cut point for AFP that would improve the early detection of this tumor while maintaining an adequate specificity of 82%. Our data suggest that for cirrhotic patients with viral etiology, an AFP > 10.9 ng/mL should trigger a CT/MRI for the diagnosis of early stage HCC. The specificity of this cutoff would be 82% alone and 80% in combination with DCP, therefore, less than 20% patients would be getting cross-sectional imaging to evaluate for HCC. While these sensitivities and specificities are reasonable, they are not optimal for HCC surveillance as the costs will be prohibitive if 20% of cirrhotic patients have to undergo repeated CT or MRI to rule out the diagnosis of HCC. This suggested new cutoff needs to be tested in large phase 3 biomarker studies (retrospective evaluation of prospectively collected specimens from cohorts of patients with cirrhosis to determine the ability of a biomarker to diagnose pre-clinical disease) to determine its applicability in HCC surveillance.
Ultrasound (US) of the liver has been recommended in the surveillance for HCC based on cohort studies (4
). US have been reported to have a sensitivity ranging from 60% to 80% in patients with HCC (24
). The drawbacks to US screening among patients with cirrhosis is that it is operator dependent, its performance may be affected by body habitus, the nodularity in cirrhosis of the liver may lead to difficulty in interpretation, agreement among radiologists has not been studied, and it is not widely available. In a large randomized trial among hepatitis B carriers in China, AFP was the sole test utilized for surveillance of HCC. The sensitivity and specificity was 80.0% and 80.9%, respectively. A third (29.6%) of the patients had stage I HCC (25
). In another large randomized study of hepatitis B carriers, HCC surveillance with AFP and US was shown to decrease mortality (26). These 2 randomized studies indicate that AFP is an important part of the surveillance strategy of hepatitis B patients at risk for HCC. These results cannot be generalized to patients with cirrhosis, in whom systematic reviews overwhelmingly showed that the performance of US is poor (10
). We did not include US in our biomarker study because it was utilized in the definition of HCC, potentially leading to verification bias, and our goal was to determine the best serum biomarker for HCC. An EDRN-defined Phase 3 study, prospective cirrhotic cohort to identify preclinical HCC, would be the best design to address the performance of US (with or without serum biomarkers).
Our current study has some limitations. It is a case-control study. A Phase 3 biomarker study is needed to determine whether biomarkers can detect preclinical HCC in a prospective manner or its performance in those with dysplastic nodules. More importantly, the prospective specimen and data collection in a Phase 3 study will eliminate potential biases because HCC status will be unknown at the time of specimen and data collection. Another limitation is that the patients enrolled were receiving attention at tertiary medical centers, and our results may not be generalizable to all patients with cirrhosis and HCC. Nevertheless, this is large multicenter study that was adequately powered, etiology of liver disease was accounted for (viral vs. non-viral), assays were performed blindly, and all geographic regions in the United States were accounted for. In addition, it provides the benchmark for studying the performance of biomarkers for the diagnosis of early HCC.
In summary, our study shows that AFP is currently the best serum biomarker for the diagnosis of early stage HCC at a new cutoff of 10.9 ng/mL. DCP performs better in those with viral etiology of liver disease. Our study helps determine the performance of AFP and DCP for early stage HCC, however these results are not optimal by themselves as surveillance tests and either new or complimentary markers are needed. An EDRN-defined Phase 3 study is needed to evaluate the performance of AFP, at its new cutoff of 10.9 ng/mL, in the detection of preclinical HCC in combination with US, DCP or other new markers.