Endoscopic Ultrasound Guided Anti-Cancer Therapy

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1 Endoscopic Ultrasound Guided Anti-Cancer Therapy Manoop S. Bhutani,MD,FASGE,FACG,FACP Professor of Medicine, Director of Endoscopic Research and Development Department of Gastroenterology, Hepatology and Nutrition Abstract INTRODUCTION Endoscopic ultrasound is an imaging modality that is a marriage of flexible endoscopes with high frequency ultrasound transducers that can be passed into the gastrointestinal tract providing high-resolution images of thoracic and abdominal organs. Interventions are possible with echoendoscopes as needles can be passed under ultrasonic guidance into various organs. Endosonography has been utilized to perform fine needle aspiration of a variety of lesions. A number of efforts are being made to utilize the targeting abilities of endosonography in a minimally invasive fashion for anti-cancer therapy and this paper will discuss the possibilities and emerging data in the field. Key Words: Endoscopic Ultrasound, Endosonography, Cancer, Fine Needle Injection, Therapy Correspondence: Manoop S. Bhutani,MD, Unit 1466, UT MD Anderson Cancer Center, Faculty Center Room , 1400 Pressler Street,Houston,TX ,USA Phone: , Fax: , Manoop.Bhutani@mdanderson.org Endoscopic ultrasound(eus) is an imaging modality that is a marriage of flexible endoscopes with high frequency ultrasound transducers mounted at the tip of endoscopes that can be passed into the gastrointestinal(gi) tract (Figure1). Usual EUS frequencies range from 5 Mega Hertz(MHz) to 20 MHz. Based on the principles of ultrasound, lower frequencies provide greater depth of penetration to allow imaging of organs and structures outside the GI tract wall as opposed to higher frequencies that enable better definition of the wall layers at the expense of depth. For example, lower frequencies, such as 7.5 MHz can image the gastrointestinal wall as five layers with total thickness of 3-4 mm that correlate with histology 1 (Figure 2) but can also image organs such as the pancreas. In comparison, a 20MHz transducer often cannot visualize extra-luminal structures, but can provide a high resolution image of the GI wall, commonly defining seven or more wall layers. Linear echoendoscopes obtain an EUS image parallel to the long axis of the echoendoscope with real-time ultrasonic imaging able to visualize the entire length of a needle with precise placement of the tip into targeted lymph nodes or masses(figure 3). EUS has become an invaluable method to diagnose and stage tumors in the thorax and the abdomen. EUS has assumed a major role in the management of gastrointestinal cancers. 2 19

2 Manoop S. Bhutani Figure 1:Tip of a linear echoendoscope. Figure 3: An echoendoscope with a needle catheter device passed through the biopsy channel for EUS guided fine needle aspiraton. Figure 2:Endoscopic ultrasound image of the normal gastric wall showing a five layer echo pattern that corresponds with histology:1: Superficial mucosa;2:deep mucosa; 3: Submucosa; 4: Muscularis propria; 5:Serosa. T: Radial endoscopic ultrasound transducer in the gastric lumen, B: Water filled balloon surrounding the transducer to create acoustic coupling. EUS is the most accurate method for local tumor(t) and N (node) staging of gastrointestinal cancers (e.g.esophageal, gastric, duodenal, ampullary and rectal). With the development of linear echoendoscopes, interventional endoscopic ultrasonography (EUS) has become a clinical reality. The widest application for interventional EUS is EUS-guided fine-needle aspiration (FNA). EUS-guided FNA is performed for sampling pancreatic masses 3, submucosal tumors, lymph nodes 4 (Figure 4), perigastrointestinal masses, adrenal glands, hilar lesions and many other locations in the body above and below the diaphragm within and just outside the gastrointestinal tract. 5, 8 Because of the access to several Figure 4: An artistic rendition of transesophageal EUS guided fine needle aspiration of a mediastinal lymph node located in the subcarina. thoracic and abdominal organs, EUS is an attractive method to possibly deliver regional cancer therapy. 20

3 Endoscopic Ultrasound Guided Anti-Cancer Therapy Through the accessory channel of the echoendoscope, a variety of needles and devices can be advanced to permit trans-luminal access to extra-luminal structures or pathology. With fine needle aspiration, a needle can be directed into a lymph node or mass under real-time EUS guidance. Potential therapeutic substances can also be injected with the same kind of needles - a procedure called fine needle injection (FNI), or needles can be advanced through the accessory channel of the echoendoscope to deliver ablative therapy such as photodynamic therapy or radiofrequency ablation. EUS GUIDED FINE NEEDLE INJECTION The precise ability of accurately placing needles into targeted structures permits the endosonographer to inject therapeutic agents directly into a specified location or into tumors. The potential advantages of this site-specific therapy include delivery of a higher concentration of therapeutic agent and avoidance of toxicity associated with systemic administration. During the same session, the endosonographer can make multiple injections at different sites if needed. EUS GUIDED CELIAC PLEXUS NEUROLYSIS Chronic abdominal pain can be a disabling symptom in patients with pancreatic cancer. Celiac plexus neurolysis has traditionally been performed percutaneously under radiologic guidance. EUS provides an alternative method for performing celiac plexus neurolysis(cpn). The celiac ganglion is consistently located at the origin of the celiac artery from the aorta. Since celiac artery is well visualized during EUS, celiac plexus neurolysis can be performed using a trans-gastric anterior approach. The most appropriate candidates for EUS guided celiac plexus neurolysis are patients with unresectable pancreatic cancer with significant pain that are completely or partially refractory to narcotic pain medications. Using ultrasonic guidance, a small caliber needle can be placed in proximity to the celiac plexus and, subsequently, anesthetic(e.g. bupivacaine) and neurolytic agents(e.g.alcohol) can be injected. The procedure is often done on an outpatient basis with total procedural time usually less than thirty minutes. Because EUS can define the celiac axis and its origin from the aorta, EUS-guided CPN has a high technical success rate and adequate safety profile. EUS-guided CPN has been described for palliation of pain in the setting of pancreatic cancer. Initial experience with this technique was published by Wiersema and Wiersema in who included 30 patients treated with EUS-guided CPN. The same group published a larger prospective study. 10 In this series of 58 patients with unresectable pancreatic cancer, a reduction in pain was achieved in 78% with a significant reduction in pain scores compared to baseline at 2 weeks; this remained significant for up to 8 weeks. In addition, patients who received adjuvant chemotherapy alone or radiation and chemotherapy had an additional benefit with CPN that was durable to 24 weeks. Common side effects of CPN include: postural hypotension (20%), transient diarrhea (15%) and transient exacerbation of abdominal pain (9%). Some advocate the prophylactic administration of half or a full liter of normal saline prior to the procedure to decrease the rates of postural hypotension. Diarrhea generally can be managed with an anti-diarrhea agent such as loperamide as needed. Reports of paraplegia after percutaneous or surgical CPN have been attributed to direct neurologic injury or spinal cord ischemia, though no similar complication has been noted after EUS-guidance. However, given the early experience with EUS-guidance, I generally include this theoretical risk in the informed consent process. EUS GUIDED ACTIVATED T LYMPHOCYTES(CYTOIMPLANT) INJECTION Cytoimplant, is a collection of activated mononuclear cells, created by incubating host and donor mononuclear cells. The incubation results in cytokine production and activation of immune effector cells. Such activated T-lymphocytes can be directly implanted into a tumor using endoscopic ultrasound guidance and fine needle injection in a minimally invasive fashion. In the initial pilot study 11 using Cytoimplant for unresectable pancreatic adenocarcinoma, Chang and colleagues used EUS-guided FNI to target injections into the main pancreatic tumor. In this study that included eight patients, either a partial or minor response was seen in slightly over a third of the patients. EUS GUIDED MODIFIED ADENOVIRUS(ONYX-015) INJECTION Another biologic agent delivered with EUS-guided FNI is ONYX-015, a replication-sensitive adenovirus. 12 The adenovirus has a deletion in the E1B-55kD gene a p53 inhibitor - and selectively replicates and lyses tumor cells that are commonly p53 deficient. In a trial with EUSguided FNI of Onyx-015, 21 patients with pancreatic cancer underwent multiple injections over several separate sessions. Traditional intravenous gemcitabine was added at day 36. With Onyx-015 alone, no patient 21

4 Manoop S. Bhutani had an objective response. However, with combination therapy, 10% had a partial response and 38% had stable disease, with a median survival of 7.5 months. Patients tolerated Onyx-015 well, however, there were some procedural complications including infections and perforations. EUS GUIDED TNFerade INJECTION Recently, Chang and colleagues reported clinical experience with a another biologic agent TNFerade. 13 TNFerade is a replication-deficient adenovirus expressing TNF-alpha under the control of a radiation inducible promoter. The investigators injected TNFerade into the tumors of patients with unresectable pancreatic adenocarcinomas. Patients received weekly injections (both EUS-guided and percutaneous) with concomitant 5-Fluorouracil(5-FU) and radiation. Although only in abstract form, results were promising. At 3 months, 11% of patients had a partial response, 31% had a minor response and 74% had tumor stabilization. The same group of investigators expanded their use of intratumoral injection of TNFerade into locally advanced esophageal cancer 14. In a multi-center trial, the investigators performed a dose-escalating study of TNFerade with concurrent neoadjuvant chemoradiation 5 FU plus cisplatin on Days 1 and 29 in patients with resectable state II and III esophageal cancer staged by computed tomography and EUS. TNFerade was administered in 1-log inter-patient dose escalations, via upper endoscopy (n=18) or EUS (n=6) once a week for 5 weeks. In the top three dose cohorts, pathologic complete response was seen in 6/15 (40%) resected tumors, and 10/17 (59%) remain disease free at a range of follow-up from 13 to 25 months. The treatment was generally well tolerated however there was one case of pulmonary embolism reported in the cohort. EUS GUIDED IMMATURE DENDRITIC CELL INJECTION Dendritic cells (DCs) are antigen-presenting cells for induction of primary T-cell dependent immune responses and may be used as anticancer vaccine therapy. Intratumoral injection of DCs into pancreatic cancer can lead to acquisition and processing by DCs of tumor antigens in situ that would then migrate to regional lymphoid organs to initiate a strong tumor-specific immune response. Irisawa and colleagues 15 believe that such intratumoral injection would be preferable to intravenous or intradermal injections. Therefore, in a pilot trial, this group performed EUS-FNI of unpulsed immature DCs into the pancreatic cancer refractory to systemic administration of gemcitabine in 7 patients. For preparation of DCs, the patients were leukophoresed to obtain a neutrophil-depleted fraction of peripheral blood mononuclear cells. Using granulocyte-macrophage colony-stimulating factor and interleukin 4, patients peripheral monocytes generated immature DCs. Intratumoral injection of 10 billion or more immature DCs was performed at 2 to 3 sites using EUS-FNI. Five of 7 patients were subjected to radiation therapy before initial EUSFNI of DCs to induce apoptosis and necrosis and to produce tumor-associated antigens for DC crosspresentation. All DC injections were tolerated without clinical toxicity. No complication associated with EUS- FNI procedure was noted. Median survival was 9.9 months. These data indicate that intratumoral injection of unpulsed DCs into the pancreatic cancer using EUSguided FNI is safe and can induce some clinical responses in patients with advanced disease. EUS GUIDED ALCOHOL INJECTION Other therapeutic agents for EUS-guided FNI include direct cytotoxins, such as alcohol or chemotherapeutic drugs. EUS-guided FNI of alcohol has been reported in case reports to successfully treat a GI stromal tumor 16 and a solid hepatic metastasis. 17 Recently, Jurgensen et al 18 successfully ablated and treated an insulinoma by EUS guided alcohol ablation in a patient who was not a good surgical candidate. Artifon and colleagues 19 on the other hand have reported EUS guided ablation of metastases to the left adrenal gland. There appears to be significant interest on the part of many groups for possibly ablating solid and cystic pancreatic tumors of the pancreas with EUS guided injection of alcohol as evidenced by the publication of pilot studies by a number of different groups on the effects of EUS guided alcohol injection in pancreatic tissue. 20, 22 An application of EUS guided FNI may be EUS-guided ethanol lavage of nonmalignant cystic tumors of the pancreas that has been proposed for cyst resolution and epithelial ablation as a less invasive option for managing pancreatic cysts, similar to methods that have been employed in cysts of the liver, kidney, and thyroid. In a study by Gan et al, patients with asymptomatic pancreatic cysts underwent ethanol lavage of increasing concentration. Of the twenty-three patients that completed 6 to 12 month follow-up, 8 patients (35%) had complete resolution of their cysts on subsequent imaging. Five patients underwent surgical resection providing histologic evidence of epithelial ablation. This experience was extended to a multicenter, randomized double-blinded study 24 of 39 patients with preliminary results showing similar success, and only one case of 22

5 Endoscopic Ultrasound Guided Anti-Cancer Therapy post-procedure pancreatitis in a patient who underwent ethanol lavage. EUS GUIDED CHEMOTHERAPY It may also be possible to deliver chemotherapeutic agents directly into a malignant or a premalignant lesion under EUS guidance. In order to improve the 35% pancreatic cystic tumor resolution rate on follow up after EUS guided alcohol injection by Gan et al, 23 another group led by Oh and colleagues 25 have investigated the feasibility of combining EUS guided alcohol injection of pancreatic cystic tumors with injection of a chemotherapeutic agent- Paclitaxel. The authors hypothesized that because of its highly hydrophobic nature, paclitaxel will exert its effect longer when instilled within a closed cavity, such as a pancreatic cyst. The hydrophobic and viscous nature of paclitaxel may reduce the possibility of it leaking through a puncture site and causing complications. The authors evaluated the safety, feasibility and response after EUSguided ethanol lavage with paclitaxel injection for treating cystic tumors of the pancreas in 14 patients.complete resolution of the cystic tumor was observed in 11 patients and partial resolution in 2 patients. The response rate of this combined approach of alcohol and paclitaxel of 78%(11of14) appears to be better compared to injection just alcohol alone(35%). 23 EUS GUIDED RADIOFREQUENCY ABLATION/ PHOTODYNAMIC THERAPY Radiofrequency ablation under ultrasound or CT scan guidance is performed percutaneously for ablation of hepatic metastases or hepatoma. A needle electrode is inserted percutaneously under image guidance into the tumor and the electrode is connected to a radiofrequency current generator.radiofrequency current is delivered to the tumor resulting in coagulation necrosis and tumor cell death. Goldberg et al 26 have investigated the feasibility of performing EUS guided radiofrequency ablation in a swine model. Thirteen Yorkshire pigs were studied under general anesthesia; the pancreas was visualized; a 19-gauge needle was inserted into the pancreatic body via a trans-gastric approach and radiofrequency current was delivered for 6 minutes. This resulted in gradually increasing hyperechoic foci around the needle tip as seen on EUS imaging. Pathological examination revealed discrete, spherical foci of coagulation necrosis that were 8-12 mm in diameter. This study demonstrated the feasibility of transgastrointestinal EUS guided radiofrequency ablation. The same group has demonstrated the possibility of EUS guided photodynamic therapy (PDT) of the pancreas in animal models. 27 Photodynamic therapy provides localized tissue ablation through the use of an appropriate photosensitizer and light exposure. Possible clinical applications suggested by the authors for EUS guided radiofrequency ablation and photodynamic therapy of the pancreas includes small functioning neuroendocrine tumors where serum levels of a hormone could be monitored to suggest complete cure as well as possibly palliation of unresectable pancreatic adenocarcinoma. HIGH INTENSITY OF FOCUSED ULTRASOUND Therapeutic ultrasound is composed of using high intensity ultrasound for anti tumor effects. Ultrasound can have thermal, mechanical and chemical effects in tumors. When sound is absorbed in living matter, it results in temperature elevation. Tumor cells are more thermosensitive than normal cells. Strong mechanical push-pull forces exerted by ultrasound lead to cellular defects. Ultrasound therapy also leads to chemical processes in cells such as easier diffusion of macromolecules. 28 High intensity ultrasound fields may be produced by focusing ultrasound waves in a very narrow focal zone to develop high intensity and is called high intensity focused ultrasound or HIFU. 29 Endoscopic application of this concept is intriguing and has been attempted by a number of groups. A canine rectal pseudo tumor model was used to investigate the possibilities of endorectal tumor ablation. 30 Another group reported feasibility study in rabbits on the suitability of high intensity focused ultrasound. 31 A transducer was developed that could be mounted at the tip of a standard duodenoscope. Transgastric endoscopic application of HIFU to the liver was attempted. The target was located in the left liver lobe, mm from the surface of the liver from the gastric side. Well-defined lesions of coagulation necrosis were created demonstrating that HIFU could be applied successfully with small transducers readily adaptable to the tip of an endoscope. The same group of investigators have also reported a feasibility study of constructing an ultrasound phased array for trans-esophageal thermal therapy. 32 Pilot results of endoscopic HIFU in a human trial have also been reported. Prat et al 33 used a flexible catheter with an 8 by 2.8 mm ultrasound transducer that had a lumen for a guidewire for intraductal HIFU during endoscopic retrograde cholangiopancreatography (ERCP). Ten patients with carcinoma of the intra or extra hepatic biliary tree or the ampulla were treated with HIFU application over 360 degrees under fluoroscopic control. No serious adverse effects occurred. Two patients were subsequently operated and were found to have extensive coagulation necrosis in one and no evidence of malignancy 23

6 Manoop S. Bhutani in the other. Another patient had complete regression of the cholangiocarcinoma; partial response was noted in 4 other patients and there was no response in 3 patients. Although the results are early, this study demonstrates the feasibility of HIFU. More studies and longer follow up will help determine the clinical role for HIFU in biliary cancers as adjunctive therapy, neoadjuvant therapy or as solo therapy. EUS GUIDED RADIATION THERAPY Eus Based Radiation Target Simulation A group in Germany 34 has developed an EUS based radiation target simulation method for treating anal cancer. This method allows application of afterloading needles with better control and optimization of the radiation target geometry. The protocol involves endosonographically restaging anal cancer six weeks after external beam radiation with 45Gy. Based on the endosonographic images a computer-generated threedimensional reconstruction of the tumor and radiation target simulation is performed. A specially designed applicator that is permeable to ultrasound waves is used for controlled transperineal implantation of afterloading needles. Radiation therapy application to the needles is performed according to the endoanal sonography based dosimetry. From , 42 EUS guided afterloading procedures were performed. Complete remission was achieved in all patients. On follow up(median 24 months) there were 2 anal recurrences. Updated results from this group in 36 patients again resulted in complete initial remission in all patients. 35 Five recurrent tumors (13.9%) were detected in a mean follow up of 44 months. The authors summarized that this method allows them to achieve a high rate of cure, low rate of complication and minimizes the chances of recurrence. EUS GUIDED FIDUCIAL PLACEMENT & BRACHYTHERAPY The CyberKnife frameless image-guided stereotactic radiosurgery system delivers radiation doses to tumors with high precision by use of real-time image guidance. Radiographic markers (or fiducials) implanted at the tumor site are used as reference points by this system to target the radiation beams. Pishvaian and colleagues 36 have recently reported EUS guided placement of fiducials. This preliminary report shows that 3 to 5 mm radiopaque metal markers (fiducials) can be placed by loading them into a 19-gauge needle, inserting the needle under EUS guidance into a tumor and then using a stylet to push the markers into the tumor. This technique of placing markers was safe and effective. EUS-guided fiducial placement was successful in a total of 11 of 13 patients (84.6%). The locations of the tumors were: retrocrural area, porta hepatis, gastroesophageal junction, mediastinum, paraspinal area and pancreas. If the use of stereotactic radiosurgery becomes more prevalent, due to the very precise visualization provided by EUS, it would be expected that EUS-guided placement of fiducials would be more accurate and safer than percutaneous computed tomography(ct) or percutaneous ultrasound(us) guided placement. 37 For small lesions that are not well defined by CT or US, EUS-guided placement might be the only way for minimally invasive placement of these markers. EUS may not be only useful in delivering non-radioactive markers for guiding external beam radiation but rather even active radiation seeds may be delivered directly into solid tumors under EUS guidance as a therapeutic modality. 38, 40 Sun et al 41 performed a human trial in 15 patients with unresectable pancreatic adenocarcinoma with a mean number of 22 radioactive seeds per patient implanted into the tumors by EUS guided needle puncture. During a follow up period of 10.6 months, the objective tumor response was classified as partial in 27% of patients, minimal in 20% patients and stable disease in 33% of patients. Clinical benefit was shown in 30% of patients, mostly due to reduction in pain. Jin et al 42 implanted radioactive Iodine-125 seeds in 25 patients with unresectable pancreatic cancers and 3 patients with metastatic cancers, none of whom had chemotherapy. The authors observed a significant drop in pain score 1 month after implantation. One seed translocated to the liver in a patient, but no other major complications were noted. It would be worthwhile to study the effectiveness of this approach in combination with conventional external beam radiation and/or chemotherapy. EUS GUIDED BILIARY ACCESS AND ANASTOMOSES ERCP with stenting is the procedure of choice for biliary drainage for malignant causes of obstructive jaundice. In many cases biliary drainage cannot be achieved via ERCP due to difficult anatomy or operator skill. EUS allows the placement of a guidewire and stent by transduodenal or transgastric puncture of a dilated biliary system without the need for an external drain. Choledochoduodenostomy with EUS can be performed in such patients by deployment of a transduodenal stent into the obstructed biliary system under EUS guidance. 43 This technique has been refined further with a transpapillary method that involves the antegrade insertion of a guidewire beyond the level of the obstruction and 24

7 Endoscopic Ultrasound Guided Anti-Cancer Therapy passage through the major papilla, allowing a rendezvous procedure leading to ERCP with biliary stent placement with EUS assistance. Kahaleh et al 44 recently described their experience with 23 patients who had unsuccessful ERCP. The biliary system was punctured with an EUS needle, and cholangiography was performed in all patients with resolution of jaundice in 21 patients. Perez-Miranda and colleagues 45 also used this technique to access the common bile duct under EUS-guidance when attempts by ERCP failed in 41 patients the majority of whom had malignant biliary obstruction. They achieved a 79% success rate in placing stents for drainage (transgastric or transduodenal). Complications occurred in 7 of 38 patients (18%) who had needle puncture, including 3 serious adverse events, mostly occurring in the early phase of the study period. 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