国际肝病采访Shih-chang Wang教授

Shih-chang Wang  Westmead Hospital, University of Sydney

Hepatology Digest: Imaging is very important in clinical hepatology. What imaging techniques could be used in diagnosis and treatment?

Prof. Wang: Generally speaking, there are 4 major areas of abnormality in the liver that we can make some contributions to with imaging. The first area is the detection of fatty liver. The gold standard in this area is biopsy. The second area looks at scanning the liver for the development of cirrhosis. The third area is the detection of liver tumours (benign or malignant) whether they arrive from the liver or have metastasised to the liver. The fourth area is interventional oncology of the liver, a relatively new technique where imaging is used to guide delivery of tumour destruction methods into the liver. These include a variety of techniques to heat or freeze the tumours or give radiotherapy or chemotherapy to the tumours.

Hepatology Digest: In your opinion, do you think MRI or CT scan is enough to clinically diagnose hepatocellular carcnoma (HCC)?

Prof. Wang: Clinically MRI or CT scan by itself is not enough to diagnose HCC as there are many images that can look like HCC. If the patient does not have the right predisposing factors to HCC such as alcoholic cirrhosis, chronic fatty liver, previous hepatitis viral infections and all of a sudden presents with HCC- like images, a biopsy will be performed as well.
 
Hepatology Digest: Your lectures are on interventional oncology of HCC. Could you please introduce the latest progress about it?

Prof. Wang: Interventional oncology is a very exciting new field in clinical cancer treatment. In the past, there were only 3 types of oncology; surgical, medical and radiotherapy oncology. Surgical oncology is still a very important technique when the disease is limited to one part of the liver. Unfortunately, only a small percentage of patients presented with HCC are suitable for complete surgical removal. This leads to interventional oncology. Chemoembolization is a means of interventional oncology developed in the late 1970s by a range of different interventionists around the world. Transarterial chemoembolization (TACE) has virtually been the first line of therapy for HCC all around the world. The traditional way of performing chemoembolization is that you take the chemotherapy agent and you emulsify it in a combination of oils labelled with iodine. This allows the droplets of emulsions to show up on X-ray. These days, very fine micro catheters are produced, which is combined with highly sophisticated methods embedding it into the tumours. Recent technology has developed a special kind of bead that is able to absorb a drug and then slowly release it. These beads are visible to the naked eye. They are half a millimetre to one millimetre in size and can be delivered through a catheter directly into the tumours. While embedded, the bead slowly releases very high concentration of the drug while the blood vessels are blocked. This is extremely effective. The only problem with this is that this procedure is relatively more expensive compared to conventional chemoembolization and it is not as readily available everywhere.

Radioembolization is about 15 years old, invented in Australia and this technology is starting to become more widely performed. This method utilises tiny microspheres labelled with highly radioactive doses of yttrium-90, which is a beta particle emitting radioisotope. These particles are delivered through a catheter into the hepatic artery.

More recently, a variety of technologies have come along either as alternative treatment or as additional treatments to chemoembolization. These include heating the tumour either with radio frequency, laser, or microwave. Radio frequency ablasion is the most commonly used. Another method of applying heat to tumours is by using high intensity focus ultrasound. This imitates the effect of using a magnifying glass in the sun to burn a hole into a piece of paper. By focusing the ultrasound and special focusing beams onto a dot the size of a millimetre until the tissue temperature rises above 60℃, the tumour tissue can be heated and destroyed. The next alternative is freezing the tumours. This method is called cryoablasion and is performed by inserting a needle into the tumor to administer liquid nitrogen to create an ice ball, theoretically freezing the tumour and destroying it. There is also a technique, which is primarily performed in Japan called trans-arterial chemotherapy infusion.

Most recently in both China and Japan, a combination approach has been adopted. Each of the above techniques are traditionally studied on their own. The problem with that is none of these are perfect and they each have limitations. Traditional chemoembolization is first performed, followed by radiofrequency ablasion immediately or within the next few days. This combination appears to more effective than either chemoembolization or radiofrequency ablasion alone, especially for medium size tumours that are the size from a golf ball to an orange. This method is probably not practical for very large size tumours and not necessary for tiny tumours.

Hepatology Digest: What do you think about chemotherapy compared to radiotherapy for HCC?

Prof. Wang: These techniques are very effective in the right patient and both have their place. Radioembolization is much more expensive than chemoembolization and it is not used as often. Typically, a patient will be given one, two or at most three radioembolization treatment. This is mainly because there are limitations to the actual dose that can be given to a patient, whereas it is often prominent for patients to be given up to ten or fifteen chemoembolization treatment over the course of their disease.