High Intensity Focused Ultrasound (HIFU) in Digestive Diseases: An Overview of Clinical Applications for Liver and Pancreatic Tumors

High Intensity Focused Ultrasound (HIFU) is an emerging technology of focal destruction in daily clinical practice. Alternative techniques of focal destruction, such as radiofrequency ablation (RFA) or more recently irreversible electroporation, have been used in digestive diseases for many years, mainly in hepatobiliary and pancreatic systems. Likewise, HIFU is currently used in the treatment of tumors located in the liver and in the pancreas. HIFU is quite exclusively applied for the treatment of malignancies, with an extracorporeal approach. Treatment of the liver is difficult because presence of the ribcage may stop propagation of ultrasound waves and respiratory motion may cause targeting problems. Pancreatic cancer is also challenging to treat with HIFU because the pancreas is a deep-seated organ surrounded by major vessels. The interposition of bowel gas may significantly obstruct the acoustic window, potentially leading to incomplete tumor ablation and injury of the interposed bowel and/or other intra-abdominal organs. The two main applications of HIFU are the treatment of hepatocellular carcinoma (HCC) and pancreatic cancer. In the management of HCC, HIFU with transarterial chemoembolization (TACE) seems to provide a survival advantage compared to TACE alone. HIFU showed similar results when compared to RFA for small tumors. HIFU could be interesting for tumors located in difficult location. For pancreatic cancer, HIFU is mostly used in the palliative setting to treat cancer-related pain. Some publications showed encouraging results about downsizing when HIFU is used in combination with chemotherapy and/or radiotherapy, which could be interesting in locally advanced tumors. This review focused on the clinical applications of HIFU in liver and pancreatic tumors.