Joshua Bornhorst, Ph.D.
Assistant Professor of Laboratory Medicine and Pathology
Division of Clinical Biochemistry
Mayo Clinic, Rochester, Minnesota
Hello, I'm Joshua Bornhorst and I'm co-director of the Clinical Immunoassay Laboratory, part of the Clinical Biochemistry Immunology Division of the Department of Laboratory Medicine and Pathology at Mayo Clinic.
For today's talk, I have no relevant financial disclosures. However, I would like to express thanks to Dr. Erica Fatica, who is a former Mayo Clinic fellow, for producing some of the cartoons used in this presentation.
The learning objectives for this talk are to review biomarker component testing for hepatocellular carcinoma; understand the GALAD score; and explore GALAD score testing at Mayo Clinic Laboratories.
Hepatocellular carcinoma, which is also known as HCC, is a primary liver cancer and it develops in patients with chronic liver disease. Its incidence is increasing both in the U.S. and worldwide, and it's the third leading cause of cancer-related death. Early detection of HCC is important, as survival rate increases as you catch it earlier, before it progresses to advanced stages.
There is a need for clinical diagnosis of HCC. While this disease can be treated effectively in early stages, most patients are not diagnosed until they're symptomatic and at higher grades and stages, which are then less responsive to therapies. A model incorporating several markers was developed for the detection of early HCC in patients with chronic liver disease, and this multianalyte model was called GALAD. This marker incorporates gender and age along with serological biomarkers of HCC.
The GALAD model, as mentioned before, incorporates both gender and age along with serological markers of HCC. These markers are AFP-L3, total AFP, and des-carboxy-prothrombin (DCP), and we'll talk about each of these markers. Together with age and gender, which are included because they are both increasing with age and male gender are associated with HCC and individuals with chronic liver disease. This forms the GALAD model, incorporating all of these.
So the GALAD model has previously been validated in different clinical cohorts with chronic liver disease for varied age and geographic distributions. This model has been validated in independent cohorts of patients from Germany, Japan, Hong Kong, and the U.S.
The actual model under the hood is a complex equation, but it's shown here, and it incorporates all of these markers together. So, the first two parts of GALAD are gender and age, as mentioned previously. Male gender and increasing age are associated with involvement of HCC. And with this model, you can calculate a GALAD score. And from the GALAD score, the probability of HCC can be further calculated, and we'll show you examples of this later on.
AFP is another component of the GALAD model, and it's the most widely available serum tumor marker utilized in the evaluation of suspected HCC. So this is a marker that if it is highly elevated it's fairly suggestive of diagnosis of HCC. However, there are increased serum concentrations of AFP found in chronic hepatitis and cirrhosis as well as other tumor types, which decreases the specificity of AFP for HCC. Finally, AFP is not expressed at high levels in all HCC patients, which results in an overall decreased sensitivity, especially in potentially curable early small tumors.
Furthermore, AFP is differentially glycosated in several hepatic diseases. One form is designated as AFP-L3. AFP-L3 is the most useful in the differential diagnosis of individuals of total serum AFP of 200 or less, which may result as from a variety of benign pathologies such as chronic liver disease or as previously mentioned, early small tumors. A percentage of AFP-L3 of 10% or more are associated with a seven-fold increased risk of developing hepatocellular carcinoma. Patients with AFP levels of 10% or more should be monitored more intensely for evidence of HCC, according to current practice guidelines.
The D component is des-gamma-carboxy-prothrombin, or DCP, which is considered a complementary biomarker to AFP and AFP-L3 percentage for assessing risk. The elevation of both AFP and DCP indicate progression of HCC, although they may reflect different features of the progression. DCP levels are shown to be correlated with tumor size and metastatic HCC, so increasing levels are associated with both of these unfavorable characteristics. DCP had the highest sensitivity in patients with HCC due to chronic hepatitis B and C infections.
So now we have several markers in our toolkit, and we can compare them directly to one another. So, in a prospective study in patients in the U.S., with established diagnosis of HCC, the sensitivities of AFP, AFP-L3, and DCP were 68%, 62%, and 73%, respectively. If you did combine the three markers the sensitivity for HCC was 86%. So while these are good markers for HCC, they're not universally sensitive or specific.
However, if you also indicate and include gender and age into this, along with these three markers, one way to visualize this is through an AUC curve. So, the GALAD model is in blue and the closer it is to the top left corner, the more sensitive and specific it is in general. So this model shows that GALAD, which incorporates all three markers and gender and age, is more sensitive and specific than each of the markers alone. In fact, if you have a GALAD score, there are different potential cutoffs that you could use resulting in different sensitivities and specificities. More commonly used GALAD cutoff of -0.76 had a 91% sensitivity and an 85% specificity for HCC detection. This is better than the individual markers and also a combination of the individual markers without gender and age.
If you want a more specific GALAD score, which is 0.88, the observed sensitivity drops to 80% but the observed specificity goes up to 97%. Some studies have also shown that the performance of the GALAD score has also been reported to be superior to ultrasound for HCC detection, which is an alternate method for detecting HCC.
So at the Mayo Clinic Laboratories, we have introduced a test which incorporates the GALAD score into the report. And this test was launched in 2020, and it's the hepatocellular carcinoma risk panel with GALAD score, and this is done in serum, and the test ID is HCCGS. And the indication is for risk assessment for development of hepatocellular carcinoma in patients with chronic liver disease.
Here is an example report. So, in this report, it does not include the age and gender, however, it has the markers, the age and gender is included in the overall patient report, but it's not shown here. So total AFP is below the reference value, percent L3 is below 10%, and des-carboxy-prothrombin is below 7.5%. So these are all marker values that are not generally associated with HCC. So, we can get a GALAD score from that, and from that, we can transform that into a probability of HCC. So in this particular case, it would be a 9% probability of HCC, which is a relatively low risk in this patient with chronic liver disease.
Shown here is a high patient. So total AFP is very high — it's above 200. L3% is 50%, which is also very high. And also des-carboxy-prothrombin is very high, indicating perhaps an advanced liver stage. So on this report, the GALAD model score is much higher and that transforms the probability of greater than 99%, which follows with a total AFP being above 200 which is strongly suggestive of the presence of HCC.
So in this report, you'll notice that we have the reference from where this GALAD score was compared, it was evaluated in the U.S. population, and then also some additional information about the study group that this result is based on. I will also point out that both tests were done on the Wako i30 instrument. And one caution about this test is that clinicians cannot use their own AFP test along with an L3%, because values obtained with different assay methods or kits may be different and cannot be used interchangeably on this report, or for calculation in the GALAD score. Also, test results cannot be interpreted as absolute evidence for the presence or absence of malignant disease.
So some more nuts and bolts of this particular assay. So this is a serum assay. It requires 0.25 milliliters, so not a lot of volume. It is frozen preferred for 90 days. However, a refrigerated sample can also be submitted, so it is not specific for malignancy. And results should be used in conjunction with information from clinical evaluation, the patient cytology, and imaging procedures. Again, the values obtained with different assay methods, i.e., AFP from another laboratory, cannot be used interchangeably in calculating this result. Test results for AFP are not interpretable if the patient is pregnant. There can be other DCP-producing tumors other than HCC that can show elevated DCP values. DCP is affected by vitamin K, so therefore medications containing antagonists to vitamin Ks or other vitamin K disruptors may cause bias in DCP results. And finally, once more, this was done on the Wako i30 using a validated GALAD score calculation.
So shown here are references and I hope you find this presentation to be informative about this multianalyte analysis index calculation.
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