Endoscopic ultrasound-guided brachytherapy of head and neck tumours. A new procedure for controlled application

Endoscopic ultrasonography-guided tumor ablation

Real-time guidance of needle advancement has transformed endoscopic ultrasound (EUS) from a diagnostic to an interventional procedure. EUS-guided fine-needle puncture has application in various interventional procedures (drainage of pseudocyst, biliary intervention, and injection of drugs). Celiac plexus or ganglion neurolysis for pain control is the major current EUS-guided fine-needle injection procedure. Feasibility and safety to accurately position needle devices and/or inject under real-time EUS imaging with precise delivery of interventional agent have expanded the use of EUS to ablate tumors. These include radiofrequency ablation, or delivery of fiducial markers, potential antitumor agents, or radioactive seeds, in the cancer mass. Minimally invasive EUS-guided antitumor therapy is primarily used for pancreatic cancer because of better anatomic access (vs other imaging modality) and the dismal prognosis (despite improvements in surgery and chemoradiation). Also, the response to parenteral chemotherapy in pancreatic cancer is poor because of suboptimal drug delivery resulting from hypovascularity and abundant desmoplasia. Other targets for EUS-guided tumor ablation are pancreatic neuroendocrine tumor and pancreatic cyst lesion, which are less aggressive and curable by resection. However, patients non-eligible for surgery may benefit from local EUS-guided ablation.

Use of ultrasound in image-guided high-dose-rate brachytherapy: enumerations and arguments

Inherently, brachytherapy is the most conformal radiotherapeutic technique. As an aid to brachytherapy, ultrasonography (USG) serves as a portable, inexpensive, and simple to use method allowing for accurate, reproducible, and adaptive treatments. Some newer brachytherapy planning systems have incorporated USG as the sole imaging modality. Ultrasonography has been successfully used to place applicator and dose planning for prostate, cervix, and anal canal cancers. It can guide placement of brachytherapy catheters for all other sites like breast, skin, and head and neck cancers. Traditional USG has a few limitations, but recent advances such as 3-dimensional (3D) USG and contrast USG have enhanced its potential as a dependable guide in high-dose-rate image-guided brachytherapy (HDR-IGBT). The authors in this review have attempted to enumerate various aspects of USG in brachytherapy, highlighting its use across various sites.

Endoscopic ultrasound-fine needle injection for oncological therapy

The minimal invasiveness and precision of endoscopic ultrasound (EUS) has lead to both its widespread use as a diagnostic and staging modality for gastrointestinal and pancreaticobiliary malignancies, and to its expanding role as a therapeutic modality. EUS-guided celiac plexus neurolysis is now a well-accepted modality for palliation of pain in patients with pancreatic cancer. EUS-guided ablation, brachytherapy, fiducial marker placement, and antitumor agent injection have been described as methods of performing minimally invasive oncological therapy. EUS-fine needle injection may be performed as adjunctive, alternative, or palliative treatment. This review summarizes the studies to date that have described these methods. A literature search using the PubMed/MEDLINE databases was performed. While most published studies to date are limited with disappointing outcomes, the concept of a role of EUS in oncological therapy seems promising.

Endoscopic Ultrasound-Guided Treatment beyond Drainage: Hemostasis, Anastomosis, and Others

Since the introduction of endoscopic ultrasound (EUS) in the 1990s, it has evolved from a primarily diagnostic modality into an instrument that can be used in various therapeutic interventions. EUS-guided fine-needle injection was initially described for celiac plexus neurolysis. By using the fundamentals of this method, drainage techniques emerged for the biliary and pancreatic ducts, fluid collections, and abscesses. More recently, EUS has been used for ablative techniques and injection therapies for patients with for gastrointestinal malignancies. As the search for minimally invasive techniques continued, EUS-guided hemostasis methods have also been described. The technical advances in EUS-guided therapies may appear to be limitless; however, in many instances, these procedures have been described only in small case series. More data are required to determine the efficacy and safety of these techniques, and new accessories will be needed to facilitate their implementation into practice.

Possibilities of interventional endoscopic ultrasound

Since endoscopic ultrasound (EUS) was developed in the 1990s, EUS has become widely accepted as an imaging tool. EUS is categorized into radial and linear in design. Radial endoscopes provide cross-sectional imaging of the mediastinum, gastrointestinal tract, liver, spleen, kidney, adrenal gland, and pancreas, which has highly accuracy in the T and N staging of esophageal, lung, gastric, rectal, and pancreatic cancer. Tumor staging is common indication of radial-EUS, and EUS-staging is predictive of surgical resectability. In contrast, linear array endoscope uses a side-viewing probe and has advantages in the ability to perform EUS-guides fine needle aspiration (EUS-FNA), which has been established for cytologic diagnosis. For example, EUS-FNA arrows accurate nodal staging of esophageal cancer before surgery, which provides more accurate assessment of nodes than radial-EUS imaging alone. EUS-FNA has been also commonly used for diagnose of pancreatic diseases because of the highly accuracy than US or computed tomography. EUS and EUS-FNA has been used not only for TNM staging and cytologic diagnosis of pancreatic cancer, but also for evaluation of chronic pancreatitis, pancreatic cystic lesions, and other pancreatic masses. More recently, EUS-FNA has developed into EUS-guided fine needle injection including EUS-guided celiac plexus neurolysis, celiac plexus block, and other “interventional EUS” procedures. In this review, we have summarized the new possibilities offered by “interventional EUS”.

Endoscopic ultrasound-guided fiducial markers and brachytherapy

Endoscopic ultrasound (EUS)-guided needle placement of small radiopaque particles paves the way for EUS-guided fiducial markers and brachytherapy. Stereotactic body radiation therapy relies on image-guided radiation therapy (IGRT), permitting escalation of radiation dose to tumors while minimizing dose to normal tissues. Fiducial markers are radiopaque spheres, coils, or seeds that are implanted in or near tumors for IGRT. Brachytherapy is a therapeutic modality for various cancers. Both require precise and minimally-invasive seed placement, which EUS provides. This article reviews recent literature regarding the safety and efficacy of these procedures and discusses novel concepts, including EUS-guided celiac ganglia radiation neurolysis.

Endoscopic ultrasound-guided fine needle injection for cancer therapy: the evolving role of therapeutic endoscopic ultrasound

Endoscopic ultrasound (EUS) is central to the diagnosis and staging of many malignancies, but now has an evolving role in cancer therapy. EUS-guided fine needle injection (FNI) is already used for palliative interventions such as treatment of pain through nerve blockade and to guide biliary decompression when conventional ERCP is not possible. More recently, EUS-FNI has been used to deliver specific anti-tumor agents for pancreatic cyst ablation and local control of tumor growth in patients with unresectable solid malignancies. The agents used to date include ethanol, brachytherapy seeds, and chemotherapeutic agents such as paclitaxel. In addition, FNI of new immunomodulating cell cultures such as mixed lymphocyte and dendritic cell cultures has also been reported, as has FNI of several different viral vectors for antitumor therapy. Although experience with these agents remains preliminary, EUS-FNI is a minimally invasive approach to deliver local antitumor agents, and is likely to have an expanding role in cancer therapy.

Interventional endoscopic ultrasonography for pancreatic cancer

Endoscopic ultrasonography (EUS) represents the combination of endoscopy and intraluminal ultrasonography. This allows use of a high-frequency transducer (5-20 MHz) that, due to the short distance to the target lesion, provides ultrasonographic images of higher resolution than those obtained from other imaging modalities, including multiple-detector-row-computed tomography, magnetic resonance imaging, and positron emission tomography. EUS is now a widely accepted modality for diagnosing pancreatic diseases. However, the most important limitation of EUS has been the lack of specificity in differentiating between benign and malignant changes. In 1992, EUS-guided fine needle aspiration (FNA) of lesions in the pancreas head was introduced into clinical practice, using a curved linear-array echoendoscope. Since then, EUS has evolved from EUS imaging to EUS-FNA and wider applications. Interventional EUS for pancreatic cancer includes EUS-FNA, EUS-guided fine needle injection, EUS-guided biliary drainage and anastomosis, EUS-guided celiac neurolysis, radiofrequency ablation, brachytherapy, and delivery of a growing number of anti-tumor agents. This review focuses on interventional EUS, including EUS-FNA and therapeutic EUS for pancreatic cancer.

Interventional EUS for the treatment of pancreatic cancer

Since the curved linear array echoendoscope (linear EUS) was developed in the 1990s, EUS has evolved from EUS imaging, to EUS-guided FNA, and now to EUS-guided fine needle injection (FNI), giving EUS even wider application. This advancement has brought "interventional EUS" into the pancreato-biliary field. Interventional EUS for pancreatic cancer includes delivery of contrast agents, drainage/anastomosis, celiac neurolysis (including ganglion neorolysis), radiofrequency ablation, photodynamic therapy, brachytherapy, and delivery of a growing number of anti-tumor agents. This review will focus on interventional EUS in the treatment of pancreatic cancer.