Self-expandable covered metallic esophageal stent impregnated with beta-emitting radionuclide: an experimental study in canine esophagus

Drug Delivery Opportunities in Esophageal Cancer: Current Treatments and Future Prospects

With one of the highest mortality rates of all malignancies, the 5-year survival rate for esophageal cancer is under 20%. Depending on the stage and extent of the disease, the current standard of care treatment paradigm includes chemotherapy or chemoradiotherapy followed by surgical esophagogastrectomy, with consideration for adjuvant immunotherapy for residual disease. This regimen has high morbidity, due to anatomic changes inherent in surgery, the acuity of surgical complications, and off-target effects of systemic chemotherapy and immunotherapy. We begin with a review of current treatments, then discuss new and emerging targets for therapies and advanced drug delivery systems. Recent and ongoing preclinical and early clinical studies are evaluating traditional tumor targets (e.g., human epidermal growth factor receptor 2), as well as promising new targets such as Yes-associated protein 1 or mammalian target of rapamycin to develop new treatments for this disease. Due the function and location of the esophagus, opportunities also exist to pair these treatments with a drug delivery strategy to increase tumor targeting, bioavailability, and intratumor concentrations, with the two most common delivery platforms being stents and nanoparticles. Finally, early results with antibody drug conjugates and chimeric antigenic receptor T cells show promise as upcoming therapies. This review discusses these innovations in therapeutics and drug delivery in the context of their successes and failures, with the goal of identifying those solutions that demonstrate the most promise to shift the paradigm in treating this deadly disease.

Companion Animals as a Key to Success for Translating Radiation Therapy Research into the Clinic

Many successful preclinical findings fail to be replicated during translation to human studies. This leads to significant resources being spent on large clinical trials, and in some cases, promising therapeutics not being pursued due to the high costs of clinical translation. These translational failures emphasize the need for improved preclinical models of human cancer so that there is a higher probability of successful clinical translation. Companion-animal cancers offer a potential solution. These cancers are more similar to human cancer than other preclinical models, with a natural evolution over time, genetic alterations, intact immune system, and a permanent adaptation to the microenvironment. These advantages have led pioneers in veterinary radiation oncology to aid human medicine by elucidating basic principles of radiation biology. More recently, the veterinary and human radiation oncology fields have increasingly collaborated to achieve advancements in education, radiotherapy techniques, and trial networks. This review describes these advancements, including significant prior research findings and the evolution of the veterinary radiation oncology discipline. It concludes by describing how companion-animal models can help shape the future of human radiotherapy. Taken as a whole, this review suggests companion-animal cancers may become widely used for preclinical radiotherapy research.

KSNM60 in Non-thyroidal Radionuclide Therapy: Leaping into the Future

This year, the Korean Society of Nuclear Medicine (KSNM) is celebrating its 60th anniversary. Treatment, as well as diagnosis, has played a very important role in the development of nuclear medicine. Since I-131 was used for thyroid therapy in 1959, other radionuclide therapy is still being used, and attempts to use new radionuclide are increasing. In this review, we briefly summarize and introduce the therapies such as radioimmunotherapy, transarterial radioembolization, radionuclide therapy for neuroendocrine tumors, peptide receptor radionuclide therapy, control of metastatic bone pain, radiation synovectomy, radionuclide brachytherapy, alpha particle therapy, and boron neutron capture therapy, which has been being attempted so far in the field of nuclear medicine.

Neutron-activated theranostic radionuclides for nuclear medicine

Theranostics in nuclear medicine refers to personalized patient management that involves targeted therapy and diagnostic imaging using a single or combination of radionuclide (s). The radionuclides emit both alpha (α) or beta (β-) particles and gamma (γ) rays which possess therapeutic and diagnostic capabilities, respectively. However, the production of these radionuclides often faces difficulties due to high cost, complexity of preparation methods and that the products are often sourced far from the healthcare facilities, hence losing activity due to radioactive decay during transportation. Subject to the availability of a nuclear reactor within an accessible distance from healthcare facilities, neutron activation is the most practical and cost-effective route to produce radionuclides suitable for theranostic purposes. Holmium-166 (166Ho), Lutetium-177 (177Lu), Rhenium-186 (186Re), Rhenium-188 (188Re) and Samarium-153 (153Sm) are some of the most promising neutron-activated radionuclides that are currently in clinical practice and undergoing clinical research for theranostic applications. The aim of this paper is to review the physical characteristics, current clinical applications and future prospects of these neutron activated radionuclides in theranostics. The production, physical properties, validated clinical applications and clinical studies for each neutron-activated radionuclide suitable for theranostic use in nuclear medicine are reviewed in this paper.

The various therapeutic applications of the medical isotope holmium-166: a narrative review

Over the years, a broad spectrum of applications of the radionuclide holmium-166 as a medical isotope has been established. The isotope holmium-166 is attractive as it emits high-energy beta radiation which can be used for a therapeutic effect and gamma radiation which can be used for nuclear imaging purposes. Furthermore, holmium-165 can be visualized by MRI because of its paramagnetic properties and by CT because of its high density. Since holmium-165 has a natural abundance of 100%, the only by-product is metastable holmium-166 and no costly chemical purification steps are necessary for production of nuclear reactor derived holmium-166. Several compounds labelled with holmium-166 are now used in patients, such Ho¹⁶⁶-labelled microspheres for liver malignancies, Ho¹⁶⁶-labelled chitosan for hepatocellular carcinoma (HCC) and [¹⁶⁶Ho]Ho DOTMP for bone metastases. The outcomes in patients are very promising, making this isotope more and more interesting for applications in interventional oncology. Both drugs as well as medical devices labelled with radioactive holmium are used for internal radiotherapy. One of the treatment possibilities is direct intratumoural treatment, in which the radioactive compound is injected with a needle directly into the tumour. Numerous other applications have been developed, like patches for treatment of skin cancer and holmium labelled antibodies and peptides. The second major application that is currently clinically applied is selective internal radiation therapy (SIRT, also called radioembolization), a novel treatment option for liver malignancies. This review discusses medical drugs and medical devices based on the therapeutic radionuclide holmium-166.

A Review of Self-Expanding Esophageal Stents for the Palliation Therapy of Inoperable Esophageal Malignancies

Esophageal cancer is a very deadly disease, killing more than 15,000 people in the United States annually. Almost 400,000 new cases happen in the worldwide every year. More than 50% esophageal cancer patients are diagnosed at an advanced stage when they need an esophageal stent to open the blocked esophagus for feeding and drinking. Esophageal stents have evolved in stages over the years. Current clinically used stents commonly include stainless steel or nitinol self-expandable metallic stent (SEMS) and self-expandable plastic stent (SEPS). There are many choices of different types of stents and sizes, with fierce competition among manufacturers. However, current stent technology, whether uncovered, partially covered, fully covered SEMS or SEPS, has their own advantages to solve the dysphagia, stricture, and fistula problems, but they also cause some clinical complications. The ideal stent remains elusive. New 3D printing technique may bring new promising potential to manufacturing personalized esophageal stents. Drug-eluting stents could be the new avenue to do more than just pry open a stricture or cover a defect in the esophageal lumen, a possibility of proving local anticancer therapy simultaneously. Additionally, the lack of esophageal cancer animal models also hinders the progress of stent development. This paper reviews these topics for a comprehensive understanding of this field. In a conclusion, the ultimate goal of the future esophageal stent would have multifunction to treat the underlying conditions and restore esophageal function to near normal.

History of the Use of Esophageal Stent in Management of Dysphagia and Its Improvement Over the Years

The art and science of using stents to treat dysphagia and seal fistula, leaks and perforations has been evolving. Lessons learnt from the deficiencies of previous models led to several improvements making stent deployment easier, and with some designs, it was also possible to remove the stents if needed. With these improvements, besides malignant dysphagia, newer indications for using stents emerged. Unfortunately, despite several decades of evolution, as yet, there is no perfect stent that "fits all." This article is an overview of how this evolution process happened and where we are currently with using stents to manage patients with dysphagia and with other esophageal disorders.

Persistent Regurgitation in Four Dogs with Caudal Esophageal Neoplasia

Esophageal neoplasia is an uncommon, but important, consideration for acute and chronic regurgitation and megaesophagus in dogs. The diagnosis can be challenging, and treatment options are often limited. This case series describes four dogs with regurgitation secondary to caudal esophageal masses. All dogs presented with regurgitation, and three of the four dogs had radiographically apparent megaesophagus. In all dogs, ancillary diagnostics revealed the presence of a caudal esophageal mass resulting in esophageal obstruction, and all mass lesions were histopathologically confirmed to be neoplastic. Treatment responses were variable, with one dog still alive 37 mo postdiagnosis at the time of manuscript preparation.

Esophageal stenting

Malignant obstruction of the esophagus is a debilitating condition, with dysphagia as its main symptom. Many patients present with advanced disease and palliative treatment is the only possibility. Since their widespread introduction 10 years ago, self-expanding metal stents have become accepted as an extremely effective method of palliating malignant dysphagia. Early reports suggesting very low complications have been superseded by results from randomized trials. It is now evident that the complication rate is significant and the need for reintervention can be as high as 50%. Modifications in stent design should reduce this reintervention rate. There are a large number of stent designs now available and it is essential that the interventional radiologist understand the particular strengths and weaknesses of each design, so that the correct choice of stent can be made for a particular patient. The most recent designs include antireflux stents and removable stents. Both represent significant advances and should reduce stent-related complications.

A rat esophageal model to investigate stent-induced tissue hyperplasia

PURPOSE

To evaluate the feasibility of stent placement and the formation of tissue hyperplasia caused by stent placement in a rat esophageal model.

MATERIALS AND METHODS

Twenty Sprague-Dawley rats were divided into four groups to assess differing stent diameters and design (group I, 4 mm diameter and a large mesh gap; group II, 5 mm diameter and a large mesh gap; group III, 5 mm diameter and a small mesh gap; and group IV, barbs added to the group III stents). Follow-up, 1-week, and 3-week esophagograms were obtained. Rats were euthanized 3 weeks after stent placement. Microscopic findings were evaluated in groups with an incidence of less than 50% stent migration.

RESULTS

Stent placement was technically successful in all rats, and there were no procedure-related complications. No esophageal perforation occurred during follow-up. The incidence of stent migration was 100%, 60%, 40%, and 0% in groups I through IV, respectively. The esophagi with stent migration showed only a small amount of tissue hyperplasia; however, esophagi without stent migration showed gross tissue hyperplasia through the mesh. The microscopic findings were evaluated in groups III and IV. The degree of inflammatory cell infiltration, papillary projection thickness, granulation tissue area, and percentage of the granulation tissue area were higher in group IV than in group III; however, there was no statistical significance.

CONCLUSIONS

Esophageal stent placement was feasible in a rat model, and formation of tissue hyperplasia was evident in rats without stent migration. With barbed stents, there was the least incidence of stent migration without esophageal perforation.

Stenting of the upper gastrointestinal tract: current status

Minimally invasive image-guided insertion of self-expanding metal stents in the upper gastrointestinal tract is the current treatment of choice for palliation of malignant esophageal or gastroduodenal outlet obstructions. A concise review is presented of contemporary stenting practice of the upper gastrointestinal tract, and the procedures in terms of appropriate patient evaluation, indications, and contraindications for treatment are analyzed, along with available stent designs, procedural steps, clinical outcomes, inadvertent complications, and future technology. Latest developments include biodegradable polymeric stents for benign disease and radioactive or drug-eluting stents for malignant obstructions.

Intraluminal implantation of radioactive stents for treatment of primary carcinomas of the peripancreatic-head region: a pilot study

BACKGROUND

Patients diagnosed with bile-duct, pancreatic-head, and ampullary carcinomas have a poor prognosis.

OBJECTIVE

This study evaluated the potential curative efficacy and safety of intraluminal brachytherapy by using radioactive stents for palliative treatment of these patients.

DESIGN AND SETTING

Patients with inoperable extrahepatic bile-duct (n = 2), pancreatic-head (n = 6), or ampullary (n = 3) carcinomas were treated by intraluminal implantation of radioactive stents designed according to a computerized treatment-planning system.

INTERVENTIONS

Both radioactive stents and commonly used self-expanding metallic or plastic stents were placed in the common bile duct (CBD) of the patients. For pancreatic carcinoma, the combination of radioactive CBD and pancreatic duct (PD) stents or only a radioactive PD stent was chosen according to the tumor position.

MAIN OUTCOME MEASUREMENTS

Survival, tumor status, and complications were assessed during the follow-up period.

RESULTS

A total of 16 radioactive stents were successively placed in all 11 patients. There were no life-threatening complications. The median survival was 150 days. After 2 months of the placement of radioactive stents, 8 patients (72.7%) had stable disease, whereas 3 patients (27.3%) showed progressive disease.

CONCLUSIONS

The combination of radioactive stents and metallic and/or plastic stents was technically feasible and tolerable in patients with advanced tumors around the pancreatic-head area.

A novel approach for treatment of unresectable extrahepatic bile duct carcinoma: design of radioactive stents and an experimental trial in healthy pigs

BACKGROUND

Patients diagnosed with extrahepatic bile duct carcinoma (EBDC) have a poor prognosis.

OBJECTIVE

The purpose of these studies was to design radioactive stents for EBDC and to evaluate the feasibility and safety of the stents in healthy pigs.

DESIGN

Plastic stents with inserted iodine-125 seeds were designed and tested in 11 healthy pigs. The pigs were divided into 4 groups on the basis of radiation doses.

INTERVENTIONS

The stents with estimated radiation dose at a 5-mm radial distance from the axis of the seeds of 30 Gy, 60 Gy, and 90 Gy were implanted in the common bile duct (CBD) in groups A, B, and C (n = 3 in each group), with the control group (n = 2) being implanted with the stents containing nonradioactive seeds.

MAIN OUTCOME MEASUREMENTS

Histologic evaluation was performed under a light microscope.

RESULTS

The procedures were successfully performed on all pigs. Severe hyperplasia of the mucosa was seen in the control group. In the experimental groups, obvious mucosal necrosis near the radioactive seeds was observed but without perforation of the CBD wall. In lower-dose groups (30 Gy), mild hyperplasia of mucosal glands with fibrosis under the necrosis layer was seen. However, after the increase of the dose, mucosal glands were disappearing without a visible mucosal layer.

CONCLUSIONS

The radioactive stents are safe at each dose in healthy pigs. Moreover, our observations indicate the feasibility to design specific radioactive stents according to the size, shape, and position of EBDC in future clinical applications.

Advances in research of esophageal stents

Esophageal stents were used initially in the palliative treatment of esophageal carcinoma to improve the life quality of the patients in the advanced stage. Along with the appearance of many new kinds of esophageal stents, esophageal stents have been used in the management of the benign esophageal strictures, and clinical effectiveness has been made. This article reviews the application of the esophageal stents in the benign and malignant esophageal strictures.

Application progress of stent placement in esophageal malignant and benign stenosis

Stent placement is widely used for palliation of dysphagia caused by advanced esophageal carcinoma. As the development of technology, many new stents are being used for clinical therapy. Some stents are added with anti-reflux valve or retrievable device, some are loaded with ¹²⁵I; the biodegradable stent are even invented. Improvement of sents can decrease many complications while elevate survival rates. Several nonsurgical palliative modalities including endoluminal laser therapy, photodynamic therapy, electrocoagulation and brachytherapy are available to recanalize malignant stenosis, but the fastest palliative method is stent placement. Reports about treating benign esophageal stricture with stents are increasing, and temporary and biodegradable stents have a better effect.

Endoscopic stenting-Where are we now and where can we go?

Self expanding metal stents (SEMS) play an important role in the management of malignant obstructing lesions in the gastrointestinal tract. Traditionally, they have been used for palliation in malignant gastric outlet and colonic obstruction and esophageal malignancy. The development of the polyflex stent, which is a removable self expanding plastic stent, allows temporary stent insertion for benign esophageal disease and possibly for patients undergoing neoadjuvant chemotherapy prior to esophagectomy. Potential complications of SEMS insertion include perforation, tumour overgrowth or ingrowth, and stent migration. Newer stents are being developed with the aim of increasing technical and clinical success rates, while reducing complication rates. Other areas of development include biodegradable stents for benign disease and radioactive or drug-eluting stents for malignant disease. It is hoped that, in the future, newer stents will improve our management of these difficult conditions and, possibly, provide prognostic as well as symptomatic benefit in the setting of malignant obstruction.

Treatment options for esophageal strictures

Esophageal strictures are a problem commonly encountered in gastroenterological practice and can be caused by malignant or benign lesions. Dysphagia is the symptom experienced by all patients, regardless of whether their strictures are caused by malignant or benign lesions. The methods most frequently used for palliation of malignant esophageal strictures are stent placement (particularly in patients with an expected survival of 3 months or less) and brachytherapy (in patients with a life expectancy of more than 3 months). Brachytherapy has been shown to be beneficial in patients with an expected survival of longer than 3 months with regard to (prolonged) dysphagia improvement, complications and quality of life. The mainstay of benign esophageal stricture treatment is dilation. Although dilation usually results in symptomatic relief, recurrent strictures do occur. In order to predict which types of strictures are most likely to recur, it is important to differentiate between esophageal strictures that are simple (i.e. focal, straight strictures with a diameter that allows endoscope passage) and those that are more complex (i.e. long (>2 cm), tortuous strictures with a narrow diameter). These complex strictures are considered refractory when they cannot be dilated to an adequate diameter. Novel treatment modalities for refractory strictures include temporary stent placement and incisional therapy.

A Novel Approach for Treatment of Unresectable Pancreatic Cancer: Design of Radioactive Stents and Trial Studies on Normal Pigs

PURPOSE

Patients diagnosed with pancreatic cancer typically have a poor prognosis. The aims of these studies were to design radioactive stents and to evaluate the feasibility and safety of the stents in animals.

EXPERIMENTAL DESIGN

To combine the effects of stents and brachytherapy, plastic stents with inserted iodine-125 seeds were designed and tested in 18 normal pigs. The pigs were divided into five groups on the basis of radiation dose. The estimated radiation dose at a 5-mm radial distance from the axis of the seeds was 50 Gy in group A, 100 Gy in group B, 150 Gy in group C, and 200 Gy in group D, with four pigs in each group. In the control group (n = 2), the same plastic stents with non-radioactive seeds were implanted in the pancreatic duct.

RESULTS

The procedures were successfully done on 14 of 18 (78%) pigs, whereas pancreatic duct perforation occurred in four pigs (22%). The thickened wall of the dilated pancreatic duct was clearly observed in the control group. However, the normal morphologic structure of the pancreatic duct wall disappeared in the experimental groups. Histopathologic examination revealed that the stents were surrounded with necrotic tissues and lateral fibrous tissues. During the follow-up period, the width of outside fibrous tissues gradually increased.

CONCLUSIONS

These results indicate that the radioactive stents are safe in all dose groups, and it is feasible to design a special radioactive stent for each patient according to the size, shape, and position of the pancreatic tumor.

Self-expandable stent loaded with 125I seeds: feasibility and safety in a rabbit model

OBJECTIVE

To evaluate technical feasibility and acute and subacute radiotolerance of a self-expandable stent loaded with (125)I seeds in the rabbit esophagus.

METHODS

A self-expandable stent designed for esophageal application was made of 0.16mm nitinol wire and loaded with (125)I seeds (CIAE-6711). Twenty-seven stents with three different radioactive dosages (n=9 in each dosage group) were implanted in the esophagus of healthy rabbits, while nine stents alone were used as controls. The stents were perorally deployed into the esophagus under fluoroscopic guidance. Radiological follow-up included plain chest film, CT scan, and barium esophagography which were undertaken in all rabbits of each group at 2, 4, and 8 weeks, respectively, which were correlated to histopathological findings. The stented esophageal segments along with their adjacent tissues were harvested for histopathological examinations.

RESULTS

The stent was successfully deployed into the targeted esophageal segment in all rabbits. Neither (125)I seeds dislodged from the stent during the deployment, nor they did during the follow-up period. The greatest (16.2Gy) absorbed dose was found in the tissue 10mm from (125)I seeds at 8 weeks. Slight epithelial hyperplasia on the stent surface and submucosal inflammatory process developed at 2 weeks, which reached the peak at 8 weeks after the procedure. Significant thickness of the esophageal muscular layer was found at 8 weeks only in the groups with (125)I seeds. On radiologic follow-up, moderate strictures on both ends of the stents developed at 4 weeks and became severe at 8 weeks after the procedure in all groups.

CONCLUSION

Deployment of a self-expandable stent loaded with (125)I seeds is technically feasible and safe within the first 8 weeks. Acute and subacute radiotolerance of the treated esophagus and its adjacent tissues by (125)I seeds is well preserved in a healthy rabbit model.

Rhenium-188 Mercaptoacetyltriglycine–filled Balloon Dilation in the Treatment of Recurrent Urethral Strictures: Initial Experience with Five Patients

PURPOSE

To evaluate the efficacy of beta-irradiation therapy with use of a rhenium-188 mercaptoacetyltriglycine ((188)Re-MAG(3))-filled balloon for the prevention of restenosis in urethral strictures refractory to repetitive surgical or interventional procedures.

MATERIALS AND METHODS

Five male patients with traumatic (n = 4) or postoperative anastomotic (n = 1) recurrent urethral strictures were included. One to four sessions of 20-30 Gy beta-irradiation at a 1-mm tissue depth with (188)Re-MAG(3)-filled balloon dilation were undertaken in each patient.

RESULTS

No procedural complications or toxicities were noted. During the mean follow-up period of 16.2 months, the stricture did not recur in two patients, whereas three patients required additional interventional procedures. In two of these patients, the treatment intervals between the required sessions were significantly prolonged. For the entire group, the mean treatment interval was prolonged from 2.2 months before (188)Re-MAG(3)-filled balloon dilation to 10.7 months after therapy.

CONCLUSION

(188)Re-MAG(3)-filled balloon dilation shows promise in preventing or delaying stricture recurrence in patients with recurrent urethral strictures.

Effects of irradiation using a radioisotope-filled balloon on tissue hyperplasia caused by stent placement in a canine urethral model

PURPOSE

To evaluate 20 Gy and 40 Gy of intraluminal beta-irradiation using a 188Re-7mercaptoacetyltriglycine (MAG3)-filled balloon catheter to reduce tissue hyperplasia caused by covered stent placement for 12 weeks of follow-up in a canine urethral model.

MATERIAL AND METHODS

Ten dogs underwent 188Re-MAG3-filled balloon dilatation immediately after stent placement; 20 Gy at 1-mm tissue depth in group I (n = 5) and 40 Gy in group II (n = 5), whereas 5 dogs (group III) underwent conventional balloon dilatation only.

RESULTS

There were no significant differences among the three groups for percentage diameter of stenosis, although this was highest in group III. There was a tendency toward lower mean thickness of the epithelial layer and the papillary projection for out-stent area, and thickness of the papillary projection and degree of inflammatory cells for instent area in groups I and II compared with group III. Thickness of the papillary projection in out-stent area was significantly different among the three groups (P = 0.031). It was significantly less thick in group I than in group III (P < 0.05), whereas group II was not significantly different from group III.

CONCLUSION

188Re-MAG3-filled balloon dilatation has the potential to reduce tissue hyperplasia after 12 weeks of follow-up in a canine urethral model. The use of 20 Gy compared to 40 Gy did not show significant differences.

New developments in palliative therapy

Over the past 5 years, new developments in the palliative treatment of incurable cancer of the oesophagus and gastro-oesophageal junction have been introduced with the aim of palliating dysphagia and improving the survival of patients. Stent placement is currently the most widely used treatment for palliation of dysphagia from oesophageal cancer. A stent offers rapid relief of dysphagia; however, current recurrent dysphagia rates vary between 30 and 40%. Recently introduced new stent designs are likely to reduce recurrent dysphagia by decreasing stent migration and non-tumoral tissue overgrowth. Intraluminal radiotherapy (brachytherapy) has been demonstrated to compare favourably with stent placement in long-term effectiveness and safety. A disadvantage of brachytherapy, however, is that one-fifth of patients need an additional treatment because of persistent tumour growth in the oesophagus. A solution may be to administer brachytherapy not in a single fraction but in multiple fractions. Finally, efforts have been undertaken to improve survival of patients by using chemotherapy. In the future, a multimodal approach--for example by combining stent placement with chemotherapy or radiotherapy--may improve the prognosis of patients without jeopardizing their quality of life.

Fluoroscopically Guided Balloon Dilation for Benign Anastomotic Stricture after Ivor-Lewis Esophagectomy: Experience in 62 Patients

PURPOSE

To evaluate the safety and clinical effectiveness of fluoroscopically guided balloon dilation in 62 patients with benign anastomotic stricture after Ivor-Lewis esophagectomy.

MATERIALS AND METHODS

Between January 1996 and June 2004, fluoroscopically guided balloon dilation was undertaken in 62 patients with benign anastomotic stricture after Ivor-Lewis esophagectomy. Radiologic images and medical records including complications were retrospectively reviewed. The maximum diameters of the balloon catheters used were 18-20 mm. Clinical success was defined by the absence of recurrent dysphagia after balloon dilation until the most recent follow-up. The Fisher exact test was used to assess the relationship of symptomatic recurrence and the balloon size, width of the stricture, and radiation therapy.

RESULTS

There were 115 sessions of balloon dilation in 62 patients (mean, 1.85 sessions per patient). Clinical success was achieved in 59 patients (95%) by means of a single dilation (n = 29) or by multiple dilations (n = 30). One patient with severe stenosis was successfully treated with temporary placement of a covered retrievable stent. Major complications such as esophageal perforation or massive bleeding did not occur. Four patients with mucosal tear (n = 3) or aspiration pneumonia (n = 1) were conservatively treated. Patients with severe stricture had more symptomatic recurrences than those with moderate stricture.

CONCLUSION

Fluoroscopically guided balloon dilation is a safe and successful treatment modality for benign anastomotic stricture after Ivor-Lewis esophagectomy.

Effects of a holmium-166 incorporated covered stent placement in normal canine common bile ducts

PURPOSE

A specially designed self-expandable covered metallic stent incorporated with beta-emitting radioisotope, Holmium-166 (Ho-166), was developed for delivering intraluminal brachytherapy as well as for internal bile drainage in malignant biliary stricture. The purpose of the study was to demonstrate the safety and tissue response of the radioactive metallic stent on the normal canine common bile duct (CBD) prior to the clinical application.

MATERIALS AND METHODS

Nitinol self-expandable stents (diameter; 4 mm, length; 20 mm) were covered with polyurethane membrane (50 microm thick) containing 21 to 135 muCi of Ho-166 (mean, 77.9 microCi). To prevent migration of stent, the membrane covered only the middle 1 cm of the stent and the ends of the stent were left uncovered. The stents were placed in the CBD of 20 healthy beagle dogs. For control, non-radioactive covered stents were placed in another three dogs. The dogs were killed 3 to 6 months after stent insertion and histopathologic examination of CBD was performed.

RESULTS

There was no stent migration in all cases. Varying degrees of papillary mucosal hyperplasia leading to significant narrowing of the lumen was observed within the lumen of the bare portion and under the mucosal surface of the non-radioactive covered stents. However, fibrosis was noted in Ho-166 coated area, instead of mucosal hyperplasia. Severity of fibrosis was correlated with estimated radiation dose. Despite high dose, there was no perforation of CBD wall. The membrane of Ho-166 coat was disrupted in some cases of 6 months follow-up.

CONCLUSIONS

Holmium-166 incorporated covered stents demonstrated fibrosis of CBD wall and inhibition of ingrowth of mucosal hyperplasia without serious complication such as perforation, while control group showed severe mucosal hyperplasia.

Esophageal palliation--photodynamic therapy/stents/brachytherapy

The optimal treatment for malignant dysphagia should be safe, effective,cost-effective, and have minimal morbidity. Photodynamic therapy,brachytherapy, and esophageal stenting all represent viable options for the palliation of malignant dysphagia. Characterization of the patients and their tumors allows individualization of the treatment and the selection of the optimal treatment for each individual patient. Institutional resources and expertise also are significant factors in treatment. Further comparative studies may help further delineate the relative merits of these treatments and the optimal treatment of patients with malignant obstruction.

Preparation and characterization of radioactive Co/188Re stents intended for lung cancer treatment using an electrodeposition method

A procedure for electroplating a Co/(188)Re alloy layer on metal coils (stents) at room temperature was developed. The electroplating of the Co/(188)Re alloy layer was carried out at a current density of 93 A m(-2) and produced a physically strong Co/(188)Re alloy layer that adhered well to a thin gold strike layer on top of the stent material. The final gold layer was also stable. An empirically-found equation correlates the radioactive electroplating efficiency factor to the concentration of the radioisotope and was used to deposit predetermined amounts of radioactivity on the stent surface. Radioactive stents can be prepared and quality control performed within 2 hours using an automated electroplater and dosimetric quality control system. The radioactivity was homogeneously distributed on the stent surface. The in vitro stability in human plasma at 37 degrees C was found to be greater than 95% for both Wallstent and Ultraflex stent after 72 hours of incubation. A clinical pilot trial is planned after successful completion of animal testing.

Reduction of Tissue Hyperplasia with a Rhenium188 Mercaptoacetyltriglycine-3–filled Balloon: Preliminary Study in a Canine Urethral Model

PURPOSE

To evaluate the efficacy of beta-radiation therapy with rhenium-188 mercaptoacetyltriglycine-3 (MAG(3))-filled balloons to reduce tissue hyperplasia secondary to stent placement in 18 canine urethras.

MATERIALS AND METHODS

Eight dogs were treated with 188-Re MAG(3)-filled balloon dilation immediately after stent placement and were killed 4 weeks later (group I, n = 4) or 8 weeks later (group II, n = 4). Five dogs were treated with 188-Re MAG(3)-filled balloon dilation 2 weeks after stent placement and were killed 4 weeks after stent placement (group III). The remaining five dogs were treated with conventional balloon dilation immediately after stent placement and were killed 4 weeks later; these animals formed the control group (group IV). Retrograde urethrography (RUG) was performed during follow-up and three histologic parameters were investigated: the number of epithelial layers, papillary projection thickness, and degree of submucosal inflammatory cell infiltration. The areas inside and outside the ends of the stents were evaluated in each case after animal sacrifice. After testing statistical significance of data for RUG and histologic findings in the four study groups, the Mann-Whitney U test was used to compare groups I and II to determine delayed effects of irradiation, groups I and III to determine benefits of delayed irradiation, groups I and IV to determine efficacy of immediate irradiation for reducing tissue hyperplasia, and groups III and IV to determine efficacy of delayed irradiation for reducing tissue hyperplasia.

RESULTS

There were no significant differences in the four study groups on RUG before animal sacrifice. Between groups I and II, group II showed significantly lower mean values in five of six histologic comparisons. Between groups I and III, group III showed significantly lower mean values in only papillary projection thickness inside the stent ends. Between groups I and IV, group I showed significantly lower mean values in all three histologic parameters outside the stent ends. Between groups III and IV, group III showed significantly lower mean values in only two histologic parameters (papillary projection thickness in the in-stent area and inflammatory cell infiltration outside the stent edges).

CONCLUSION

beta-Irradiation with use of a 188-Re MAG(3)-filled balloon shows the potential to reduce tissue hyperplasia secondary to stent placement in a canine urethral model. Treatment with 188-Re MAG(3)-filled balloons at the time of stent placement shows not only favorable outcomes for reducing tissue hyperplasia but also improved delayed effects until 8 weeks.

Endoscopic therapeutic esophageal interventions: old, new, borrowed and . . . methylene blue?

PURPOSE OF REVIEW

Endoscopic interventions in the esophagus continue to evolve. This article reviews some of the notable advances over the past year in endoscopic therapy for the esophagus.

RECENT FINDINGS

In 2002 several endoscopic therapies were reintroduced or modified. Ablative treatments, including Nd:YAG laser, photodynamic therapy, and thermal contact treatments have been shown to be effective for Barrett esophagus and some early esophageal cancers. The addition of endoscopic mucosal resection may improve these therapies. Endoscopic stenting remains the dominant endoscopic palliative modality for unresectable esophageal cancers, and modifications of this therapy have focused on reducing side effects and complications. Innovations in endoscopic treatments for strictures and bleeding esophageal varices have been proposed and may improve outcomes, although probably only marginally. Additional endoscopic antireflux procedures have been introduced, although the results of long-term studies still need to be published before their place in the treatment of gastroesophageal reflux disease can be determined.

SUMMARY

Rather than heralding novel endoscopic therapeutics, 2002 was a year of retooling and refining existing techniques.

New approach to malignant strictures of the esophagus

Primary esophageal cancer is the most common cause of malignant esophageal stricture. Prognosis and treatment outcomes vary with the stage of the disease. Endoscopic ultrasound has a high accuracy rate for local and regional staging. Surgery is curative for early cancer. Endoscopic mucosal resection, photodynamic therapy, or brachytherapy can be used with curative intent for early cancer, especially in patients with comorbid conditions precluding surgery. Unfortunately, the majority of patients with esophageal cancer present with advanced disease. The primary aim in these patients is to alleviate symptoms with a minimum of side effects and reinterventions. Palliative surgery or chemoradiotherapy can be associated with high morbidity and mortality rates. Several endoscopic techniques for palliation are available, and all have the potential of significantly improving swallowing. The choice of a particular endoscopic approach is usually determined by local expertise and characteristics of the stricture.