Contrast-enhanced endoscopic ultrasonography can predict a higher malignant potential of gastrointestinal stromal tumors by visualizing large newly formed vessels

EUS-Guided Diagnosis of Gastric Subepithelial Lesions, What Is New?

Gastric subepithelial lesions (SELs) are intramural lesions that arise underneath the gastric mucosa. SELs can be benign, but can also be malignant or have malignant potential. Therefore, correct diagnosis is crucial. Endosonography has been established as the diagnostic gold standard. Although the identification of some of these lesions can be carried out immediately, solely based on their echo characteristics, for certain lesions histological examination is necessary. Sometimes histology can be inconclusive, especially for smaller lesions. Therefore, new methods have been developed in recent years to assist decision making, such as contrast enhanced endosonography, EUS elastography, and artificial intelligence systems. In this narrative review we provide a complete overview of the gastric SELs and summarize the new data of the last ten years concerning the diagnostic advances of endosonography on this topic.

Endoscopic Ultrasound Advanced Techniques for Diagnosis of Gastrointestinal Stromal Tumours

Gastrointestinal Stromal Tumors (GISTs) are subepithelial lesions (SELs) that commonly develop in the gastrointestinal tract. GISTs, unlike other SELs, can exhibit malignant behavior, so differential diagnosis is critical to the decision-making process. Endoscopic ultrasound (EUS) is considered the most accurate imaging method for diagnosing and differentiating SELs in the gastrointestinal tract by assessing the lesions precisely and evaluating their malignant risk. Due to their overlapping imaging characteristics, endosonographers may have difficulty distinguishing GISTs from other SELs using conventional EUS alone, and the collection of tissue samples from these lesions may be technically challenging. Even though it appears to be less effective in the case of smaller lesions, histology is now the gold standard for achieving a final diagnosis and avoiding unnecessary and invasive treatment for benign SELs. The use of enhanced EUS modalities and elastography has improved the diagnostic ability of EUS. Furthermore, recent advancements in artificial intelligence systems that use EUS images have allowed them to distinguish GISTs from other SELs, thereby improving their diagnostic accuracy.

The value of contrast-enhanced harmonic endoscopic ultrasound in differential diagnosis and evaluation of malignant risk of gastrointestinal stromal tumors (<50mm)

OBJECTIVES

Contrast-enhanced harmonic endoscopic ultrasound (CEH-EUS) has been used in the differential diagnosis of benign and malignant tumors by visualization of tumor microcirculation and perfusion. However, its diagnostic role in submucosal tumors (SMTs), especially leiomyomas and gastric submucosal tumors (GISTs) was rarely studied. The aim of this study was to analyze the diagnostic role of CEH-EUS for SMTs (<50 mm) and the value of assessing the malignant potential of GISTs.

MATERIALS AND METHODS

We retrospectively included patients with tumors <50 mm in diameter who underwent preoperative EUS and CEH-EUS examination and had pathologically confirmed as leiomyomas and GISTs. To analyze the imaging features of CEH-EUS with pathological diagnosis as the gold standard and evaluate its diagnostic value.

RESULTS

This study included 10 cases of leiomyomas and 38 cases of GISTs. Under CEH-EUS detection, 86.9% of GISTs showed hyper-enhancement, 89.5% showed diffuse enhancement, 39.5% showed non-enhancing spots, and 97.4% showed obvious capsule enhancement. In contrast, the leiomyoma cases mostly showed hypo-enhancement (50.0%) or non-enhancement (30.0%) (p < 0.05). Then, the value of CEH-EUS in the differential diagnosis of benign and malignant tumors based on blood flow is significantly higher than that of B-EUS. Signal appearance time was significantly faster in the intermediate-high risk GISTs than in the very low-low risk group (5.1 s versus 15.5 s, p < 0.05), and the AUROC values predicted the risk at this time to be 0.903 (0.763-0.975). Heterogeneous perfusion and non-enhancing spots were also more common in the intermediate-high risk group. Univariate and multivariate analysis revealed that intratumoral irregularitie was an independent predictor of moderate to high risk (OR 3.99, 95%CI 1.04-90.95), with sensitivity, specificity and accuracy of 73.33%, 91.30% and 84.21%, respectively.

CONCLUSIONS

Through this study, CEH-EUS has a good differential diagnostic ability for leiomyomas and GISTs, and has a high value in predicting the risk of GISTs.

Usefulness of Contrast-Enhanced Harmonic Endoscopic Ultrasonography for Diagnosis of Malignancy in Intraductal Papillary Mucinous Neoplasm

Intraductal papillary mucinous neoplasms (IPMNs) have a wide pathologic spectrum and it can be difficult to diagnose malignancy, including pathological grade. The aim of this study was to evaluate contrast-enhanced harmonic endoscopic ultrasonography (CH-EUS) for the diagnosis of malignant IPMN and IPMN-associated invasive carcinoma (invasive IPMC). From 5009 patients diagnosed with IPMN at Wakayama medical university between December 2009 and December 2021, 115 patients who underwent contrast-enhanced computed tomography (CE-CT), conventional EUS, CH-EUS, and surgical resection were enrolled. The detection of mural lesions was compared with pathological findings. Malignant IPMN and invasive IPMC were also assessed according to mural lesion size and vascularity on CH-EUS. CH-EUS and conventional EUS showed significantly higher accuracy than CE-CT in the detection of mural nodules (92%, 83%, and 72%, respectively) and diagnosis of malignant IPMN (75%, 73%, and 63%, respectively). An early wash-out pattern on CH-EUS was observed in significantly more patients with invasive IPMC than in those with low-, intermediate-, or high-grade dysplasia. When compared with CE-CT, CH-EUS was significantly more accurate for detecting mural nodules and more useful for diagnosing malignant IPMN. The vascular pattern on CH-EUS was also useful for diagnosing invasive IPMC.

Angiogenesis in gastrointestinal stromal tumors: From bench to bedside

Gastrointestinal stromal tumors (GISTs) are rare neoplasms with an estimated incidence from 0.78 to 1-1.5 patients per 100000. They most commonly occur in the elderly during the eighth decade of life affecting predominantly the stomach, but also the small intestine, the omentum, mesentery and rectosigmoid. The available treatments for GIST are associated with a significant rate of recurrent disease and adverse events. Thorough understanding of GIST’s pathophysiology and translation of this knowledge into novel regimens or drug repurposing is essential to counter this challenge. The present review summarizes the existing evidence about the role of angiogenesis in GIST’s development and progression and discusses its clinical underpinnings.

The necessarity of treatment for small gastric subepithelial tumors (1-2 cm) originating from muscularis propria: an analysis of 972 tumors

Background and objectives

Up till now, there are still controversies about the specific indication of endoscopic resection for small gastric subepithelial tumors (gSETs) originating from muscularis propria. We aimed to investigate the safety of endoscopic resection and postoperative pathology analysis.

Method

The patients with primary small gSETs originating from muscularis propria, treated by endoscopic resection in the endoscopic center of Shengjing Hospital between January, 2011 and September, 2019 were enrolled. The complete resection rate, adverse events and clinicopathological features were recorded.

Result

A total of 936 patients with 972 gastric SETs ≤ 2 cm originating from muscularis propria were included in our study. All the lesions were successfully treated by endoscopic resection. Nearly half of lesions were proved to be gastrointestinal stromal tumor (GIST) [n = 411 (42.3%)] according to postoperative pathology. All the objects were further subdivided into 2 groups, ≤ 1 cm, > 1 and ≤ 2 cm gSETs. The risk of gastric GIST of intermediate/high risk in the group (> 1 and ≤ 2 cm gSETs) is 8.41 times as that of gastric GIST in the group (the size of gastric ≤ 1 cm gSETs) (P < 0.05).

Conclusion

Endoscopic resection is a safe and effective treatment for small gSETs. gSETs (1–2 cm) is more risky than gSETs (≤ 1 cm) and should be resected. This should be evaluated by further studies.

Endoscopic management of subepithelial lesions including neuroendocrine neoplasms: European Society of Gastrointestinal Endoscopy (ESGE) Guideline

1: ESGE recommends endoscopic ultrasonography (EUS) as the best tool to characterize subepithelial lesion (SEL) features (size, location, originating layer, echogenicity, shape), but EUS alone is not able to distinguish among all types of SEL.Strong recommendation, moderate quality evidence. 2: ESGE suggests providing tissue diagnosis for all SELs with features suggestive of gastrointestinal stromal tumor (GIST) if they are of size > 20 mm, or have high risk stigmata, or require surgical resection or oncological treatment.Weak recommendation, very low quality evidence. 3: ESGE recommends EUS-guided fine-needle biopsy (EUS-FNB) or mucosal incision-assisted biopsy (MIAB) equally for tissue diagnosis of SELs ≥ 20 mm in size.Strong recommendation, moderate quality evidence. 4: ESGE recommends against surveillance of asymptomatic gastrointestinal (GI) tract leiomyomas, lipomas, heterotopic pancreas, granular cell tumors, schwannomas, and glomus tumors, if the diagnosis is clear.Strong recommendation, moderate quality evidence. 5: ESGE suggests surveillance of asymptomatic esophageal and gastric SELs without definite diagnosis, with esophagogastroduodenoscopy (EGD) at 3-6 months, and then at 2-3-year intervals for lesions < 10 mm in size, and at 1-2-year intervals for lesions 10-20 mm in size. For asymptomatic SELs > 20 mm in size that are not resected, ESGE suggests surveillance with EGD plus EUS at 6 months and then at 6-12-month intervals.Weak recommendation, very low quality evidence. 6: ESGE recommends endoscopic resection for type 1 gastric neuroendocrine neoplasms (g-NENs) if they grow larger than 10 mm. The choice of resection technique should depend on size, depth of invasion, and location in the stomach.Strong recommendation, low quality evidence. 7: ESGE suggests considering removal of histologically proven gastric GISTs smaller than 20 mm as an alternative to surveillance. The decision to resect should be discussed in a multidisciplinary meeting. The choice of technique should depend on size, location, and local expertise.Weak recommendation, very low quality evidence. 8: ESGE suggests that, to avoid unnecessary follow-up, endoscopic resection is an option for gastric SELs smaller than 20 mm and of unknown histology after failure of attempts to obtain diagnosis.Weak recommendation, very low quality evidence. 9: ESGE recommends basing the surveillance strategy on the type and completeness of resection. After curative resection of benign SELs no follow-up is advised, except for type 1 gastric NEN for which surveillance at 1-2 years is advised.Strong recommendation, low quality evidence. 10: For lower or upper GI NEN with a positive or indeterminate margin at resection, ESGE recommends repeating endoscopy at 3-6 months and another attempt at endoscopic resection in the case of residual disease.Strong recommendation, low quality evidence.

Comparison of Computed Tomography Features of Gastric and Small Bowel Gastrointestinal Stromal Tumors With Different Risk Grades

OBJECTIVE

This study aimed to compare the computed tomography (CT) features of gastric and small bowel gastrointestinal stromal tumors (GISTs) and further identify the predictors for risk stratification of them, respectively.

METHODS

According to the modified National Institutes of Health criteria, patients were classified into low-malignant potential group and high-malignant potential group. Two experienced radiologists reviewed the CT features including the difference of CT values between arterial phase and portal venous phase (PVPMAP) by consensus. The CT features of gastric and small bowel GISTs were compared, and the association of CT features with risk grades was analyzed, respectively. Determinant CT features were used to construct corresponding models.

RESULTS

Univariate analysis showed that small bowel GISTs tended to present with irregular contour, mixed growth pattern, ill-defined margin, severe necrosis, ulceration, tumor vessels, heterogeneous enhancement, larger size, and marked enhancement compared with gastric GISTs. According to multivariate analysis, tumor size (P < 0.001; odds ratio [OR], 3.279), necrosis (P = 0.008; OR, 2.104) and PVPMAP (P = 0.045; OR, 0.958) were the independent influencing factors for risk stratification of gastric GISTs. In terms of small bowel GISTs, the independent predictors were tumor size (P < 0.001; OR, 3.797) and ulceration (P = 0.031; OR, 4.027). Receiver operating characteristic curve indicated that the CT models for risk stratification of gastric and small bowel GISTs both achieved the best predictive performance.

CONCLUSIONS

Computed tomography features of gastric and small bowel GISTs are different. Furthermore, the qualitative and quantitative CT features of GISTs may be favorable for preoperative risk stratification.

Diagnosis of gastric submucosal tumors and estimation of malignant risk of GIST by endoscopic ultrasound. Comparison between B mode and contrast-harmonic mode

BACKGROUND

standard B-mode EUS assessment and EUS-guided tissue acquisition present sub-optimal diagnostic yield in the differential diagnosis of gastric submucosal tumors (SMTs).

AIMS

to evaluate the performances of contrast-enhanced harmonic endoscopic ultrasonography (CH-EUS) to differentiate gastric SMTs and predict malignancy risk of gastrointestinal stromal tumors (GIST).

METHODS

a retrospective analysis was performed retrieving consecutive patients with gastric SMTs who underwent EUS between 2009 and 2014. Patients with available EUS video recordings and histological diagnosis were included. De-identified videos were presented to experts who made a diagnosis on B-mode EUS and CH-EUS.

RESULTS

fifty-four patients (29 female, 64-year-old) were included. Final diagnoses were 40 GISTs (8 high-grade), 9 leiomyomas, 5 rare SMTs. The sensitivity, specificity, and accuracy of B-mode and CH-EUS for the differential diagnosis of GIST were 95.0% vs. 85.0%, 57.1% for both techniques, and 85.2% vs. 77.8%, respectively. The sensitivity, specificity, and accuracy of B-mode and CH-EUS for the estimation of the malignancy GISTs risk were 62.5% vs. 100%, 83.3% vs. 82.1%, and 78.9% vs. 86.1%, respectively.

CONCLUSIONS

CH-EUS showed better diagnostic performance than B-mode EUS in differentiating leiomyomas and risk stratification of GIST. When considering high-grade GISTs, the addition of CH-EUS allowed an improvement in diagnostic accuracy.

Novel endoscopic ultrasonography imaging technique for visualizing microcirculation without contrast enhancement in subepithelial lesions: Prospective study

OBJECTIVES

Detective flow imaging for endoscopic ultrasonography (DFI?EUS) is a new imaging modality developed for detecting fine vessels without using ultrasound contrast agents. This study aimed to evaluate its utility by comparing it with a type of directional power Doppler (eFLOW) for subepithelial lesions (SELs).

METHODS

Between January 2019 and January 2020, 28 patients with SELs undergoing DFI?EUS and eFLOW?EUS were enrolled. DFI?EUS and eFLOW?EUS assessing the vascularity in SELs were compared in terms of the rates of identification of intratumoral vessels. We also investigated how large vessels were depicted in both modalities based on surgical specimens as well as the detection rates of intratumoral vessels in gastrointestinal stromal tumors (GISTs) and non?GISTs using either DFI?EUS or eFLOW?EUS.

RESULTS

Among 28 patients, 23 with pathological confirmation by EUS?guided fine?needle aspiration biopsy (EUS?FNAB) specimens were included. Of those 23 patients, the 10 who underwent surgical resection were selected for analysis. The rate of detection of intratumoral vessels in SELs was significantly higher on DFI?EUS (80%) than on eFLOW?EUS (30%) (P\xA0=\xA00.03). Comparison with surgical specimens revealed that detection rate for vessels with maximum size of less 1000\xA0μm was higher in DFI?EUS (66%) than that in eFLOW?EUS (0%). GIST patients had significantly higher positive rates (90%) of intratumoral vessels than non?GIST patients (31%) on DFI in 23 cases including EUS?FNAB specimens (P\xA0=\xA00.045).

CONCLUSIONS

Detective flow imaging?EUS is more sensitive for depicting intratumoral vessels than eFLOW?EUS. Evaluation of intratumoral vessels on DFI?EUS is useful for identifying GISTs without contrast agents.

The Asian Federation of Societies for Ultrasound in Medicine and Biology (AFSUMB) Guidelines for Contrast-Enhanced Endoscopic Ultrasound

The Asian Federation of Societies for Ultrasound in Medicine and Biology aimed to provide information on techniques and indications for contrast-enhanced harmonic endoscopic ultrasound (CH-EUS), and to create statements including the level of recommendation. These statements are based on current scientific evidence reviewed by a Consensus Panel of 15 internationally renowned experts. The reliability of clinical questions was measured by agreement rates after voting. Six statements were made on techniques, including suitable contrast agents for CH-EUS, differences between contrast agents, setting of mechanical index, dual imaging and duration and phases for observation. Thirteen statements were made on indications, including pancreatic solid masses, pancreatic cancer staging, pancreatic cystic lesions and mural nodules, detection of subtle pancreatic lesions, gallbladder sludge and polyps, hepatic lesions, lymph nodes, subepithelial lesions, visceral vascular diseases, guidance of fine needle aspiration and evaluation for local therapy. These international expert consensus guidelines will assist endosonographers in conducting CH-EUS according to evidence-based information.

Predicting Malignancy Risk in Gastrointestinal Subepithelial Tumors with Contrast-Enhanced Harmonic Endoscopic Ultrasonography Using Perfusion Analysis Software

Background/Aims

Contrast-enhanced harmonic endoscopic ultrasonography (CEH-EUS) is a promising imaging modality that can differentiate subepithelial tumors (SETs) by detecting the degree of enhancement. However, whether CEH-EUS alone can predict the malignancy risk of gastrointestinal stromal tumors (GISTs) remains unclear. This study aimed to evaluate the feasibility of CEH-EUS by using perfusion analysis software for distinguishing among SETs and predicting the malignancy risk of GISTs.

Methods

We retrospectively included patients with SETs who underwent preoperative CEH-EUS. In this study, 44 patients with histologically proven GISTs and benign SETs were enrolled. Perfusion analysis was performed using perfusion quantification software. Peak enhancement (PE), wash-in rate (WiR), wash-in perfusion index (WiPI), and wash-in and wash-out areas under the time-intensity curve (WiWoAUC) were calculated and compared between the GISTs and benign SETs.

Results

When we allocated the enrolled patients into the leiomyoma group and low- and high-grade malignancy GIST groups, significant statistical differences in PE (p<0.001), WiR (p=0.009), WiPI (p<0.001), and WiWoAUC (p<0.001) were identified in the high-grade malignancy group compared with the leiomyoma group.

Conclusions

CEH-EUS with perfusion analysis using perfusion analysis software could be a quantitative and independent method for predicting malignancy risk in gastrointestinal SETs.

Contrast Enhanced Endoscopic Ultrasound Imaging for Gastrointestinal Subepithelial Tumors

Subepithelial tumors are divided into benign subepithelial and potentially malignant gastrointestinal stromal tumors. It is difficult to distinguish between these tumor types. Contrast-enhanced harmonic endoscopic ultrasound is reportedly useful for diagnosing subepithelial tumors, can be safely and easily performed by understanding the principle and method, and can be used to distinguish between tumor types with high sensitivity on the basis of differences in contrast effect. The generated image shows a hyperenhancement pattern in gastrointestinal stromal tumors (sensitivity, 78%-100%; specificity, 60%-100%; accuracy, 60%-100%) and hypoenhancement pattern in benign subepithelial tumors. Contrast-enhanced harmonic endoscopic ultrasound can be used to estimate the malignancy potential of gastrointestinal stromal tumors by evaluating the uniformity of the contrast and the blood vessels inside the tumor, with abnormal intra-tumor blood vessels, heterogeneous enhancement, and non-enhancing spots suggesting malignancy. Contrast-enhanced harmonic endoscopic ultrasound has a higher sensitivity than other imaging modalities for the detection of vascularity within gastrointestinal stromal tumors. Additionally, it has been reported that treatment effects can be estimated by evaluating the blood flow in the gastrointestinal stromal tumor before and after treatment with tyrosine kinase inhibitors using contrastenhanced ultrasound. However, there will be subjective-bias and the results depends on the performer's skill.

Value of contrast-enhanced harmonic endoscopic ultrasonography in differentiating between gastrointestinal stromal tumors: A meta-analysis

OBJECTIVE

Contrast-enhanced harmonic endoscopic ultrasonography (CH-EUS) is a valuable device to diagnose and determine the malignant potential of gastrointestinal stromal tumors (GIST) as early as possible when making clinical therapeutic decisions. This study aimed to estimate the ability of CH-EUS to discriminate between GIST and benign submucosal lesions (SML) and to predict their malignant potential.

METHODS

PubMed, MEDLINE, EMBASE, the Web of Science, and Cochrane Central Register of Controlled Trials databases were screened. Using the data provided in the literatures, 2 × 2 tables were constructed to obtain the pooled sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio. A receiver operating characteristic (ROC) curve was generated and the area under the ROC curve (AUROC) was calculated.

RESULTS

Four studies with a total of 187 patients were identified to evaluate the value of CH-EUS in discriminating between GIST and benign SML. The pooled sensitivity, specificity, and AUROC were 89% (95% CI 0.82-0.93), 82% (95% CI 0.66-0.92), and 0.89, respectively. Five studies including 143 patients were analyzed to assess the accuracy of CH-EUS in determining the malignant potential of GIST. The pooled sensitivity, specificity, and AUROC curve of CH-EUS were 96% (95% CI 0.90-0.99), 53% (95% CI 0.40-0.66), and 0.92, respectively.

CONCLUSIONS

CH-EUS is a safe, noninvasive method that can distinguish between GIST and benign subepithelial lesions and to predict their malignant potential to a certain extent. Large-scale, multicenter prospective studies are needed in the future.

Clinical Presentation of Gastrointestinal Stromal Tumors

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms of the gastrointestinal tract. They constitute 1-2% of all gastrointestinal neoplasms but are the most common subtype of soft tissue sarcomas, accounting for 20-25%. In the late 1990s, GISTs were more and more recognized as a particular tumor entity. The tumors are supposed to originate from the interstitial pacemaker cells of Cajal. They are usually well circumscribed and can be located in every part of the tubular gastrointestinal tract. Most often GISTs occur in the stomach, followed by the small bowel and colon/rectum. In contrast to epithelial tumors, GISTs grow transmurally and submucosal. GISTs can be found with highly variable growth features including tumors with intraluminal, intra- or transmural, and pedunculated appearance. Here we describe the most common clinical presentation of GISTs on the basis of our 809 patients managed from 2004 to 2017. The median age of our patients was 59 years and the average size of GIST was 75 mm (range: 4 mm to 35 cm). The clinical presentation is very heterogeneous, depending on tumor site, size, and growth pattern. GISTs of the stomach is the group with the lowest rate of acute or emergency symptoms with 31%, followed by GISTs of the duodenum with 42%, whereas GISTs of the small bowel show acute symptoms in more than 50% of the cases and have an emergency surgery rate of almost 15%. Many patients are diagnosed accidentally, through screening examinations, or with latent, unspecific symptoms.

Surgical treatment of gastrointestinal stromal tumors of the duodenum: a literature review

Background

Gastrointestinal stromal tumors (GIST) are the most frequent mesenchymal tumours in the digestive tract. The duodenal GIST (dGIST) is the rarest subtype, representing only 4-5% of all GIST, but up to 21% of the resected ones. The diagnostic and therapeutic management of dGIST may be difficult due to the rarity of this tumor, its anatomical location, and the clinical behavior that often mimic a variety of conditions; moreover, there is lack of consent for their treatment. This study has evaluated the scientific literature to provide consensus on the diagnosis of dGIST and to outline possible options for surgical treatment.

Methods

An extensive research has been carried out on the electronic databases MEDLINE, Scopus, EMBASE and Cochrane to identify all clinical trials that report an event or case series of dGIST.

Results

Eighty-six studies that met the inclusion criteria were identified with five hundred forty-nine patients with dGIST: twenty-seven patients were treated with pancreatoduodenectomy and ninety-six with only local resection (segmental/wedge resections); in four hundred twenty-six patients it is not possible identify the type of treatment performed (pancreatoduodenectomy or segmental/wedge resections).

Conclusions

dGISTs are a very rare subset of GISTs. They may be asymptomatic or may involve symptoms of upper GI bleeding and abdominal pain at presentation. Because of the misleading clinical presentation the differential diagnosis may be difficult. Tumours smaller than 2 cm have a low biological aggressiveness and can be followed annually by endoscopic ultrasound. The biggest ones should undergo radical surgical resection (R0). In dGIST there is no uniformly adopted surgical strategy because of the low incidence, lack of experience, and the complex anatomy of the duodenum. Therefore, individually tailored surgical approach is recommended. R0 resection with 1-2 cm clear margin is required. Lymph node dissection is not recommended due to the low incidence of lymphatic metastases. Tumor rupture should be avoided.

Contrast Enhanced Harmonic Endoscopic Ultrasound: A Novel Approach for Diagnosis and Management of Gastrointestinal Stromal Tumors

The histologic analysis of gastrointestinal stromal tumors (GISTs) is a common method to detect the mitotic activity and to subsequently determine the risk of GISTs for malignancy. The potential false negative error due to inadequate yield of specimens and actual determination of malignancy risk requires analysis of the whole tumor. We aimed to assess the role of contrast enhanced endoscopic ultrasound (CE-EUS) in the management of GISTs. Two authors individually did review of English literatures to identify nine peer-reviewed original articles using keywords- contrast endoscopic ultrasound, GIST and submucosal tumor. Studies were heterogeneous in their aims looking either at differentiating submucosal lesions from GISTs, estimating malignant potential of GISTs with histologic correlation or studying the role of angiogenesis in malignant risk stratification. CE-EUS had moderate to high efficacy in differentiating GISTs from alternative submucosal tumors. CE-EUS had a higher sensitivity than EUS-guided fine needle aspiration, contrast computed tomography and Doppler EUS for detection of neo-vascularity within the GISTs. However, the evidence of abnormal angiogenesis within GIST as a prognostic factor needs further validation. CE-EUS is a non-invasive modality, which can help differentiate GISTs and provide valuable assessment of their perfusion patterns to allow better prediction of their malignant potential but more experience is needed.

Present status and perspectives of endosonography 2017 in gastroenterology

Endoscopic ultrasound has become an essential tool in modern gastroenterology and abdominal surgery. Compared with all other endoscopic methods, it has the most potential for innovation and its future looks bright. Thus, we compiled this summary of established and novel applications of endoscopic ultrasound methods to inform the reader about what is already possible and where future developments will lead in improving patient care further. This review is structured in four parts. The first section reports on developments in diagnostic endoscopic ultrasound, the second looks at semi-invasive endoscopic ultrasound, and the third discusses advances in therapeutic endoscopic ultrasound. An overview on the future prospects of endoscopic ultrasound methods concludes this article.

New Imaging Techniques for Endoscopic Ultrasonography: Contrast-Enhanced Endoscopic Ultrasonography

Conventional endoscopic ultrasonography (EUS) has limitations in the diagnosis of solid masses. Because most are depicted as a hypoechoic mass, without cytology or biopsy, it can be difficult to distinguish inflammatory masses from malignancy. Recently developed, contrast-enhanced harmonic EUS (CH-EUS) has improved characterization of digestive lesions by depicting microvessels and parenchymal perfusion, particularly for differentiating pancreatic cancer from other pancreatic solid lesions, identifying mural nodules in intraductal papillary mucinous neoplasms, and estimating malignant potential of gastrointestinal stromal tumors. CH-EUS is complementary to EUS-guided fine-needle aspiration for diagnosing pancreatic lesions, staging, and predicting chemotherapy response.

A case of successful transluminal drainage of walled-off necrosis under contrast-enhanced harmonic endoscopic ultrasonography guidance

We report a case of successful transluminal drainage of walled-off necrosis (WON) under contrast-enhanced harmonic endoscopic ultrasonography (CH-EUS) guidance. Recently, EUS-guided transluminal drainage (EUS-TD) of WON has been increasingly used as a minimally invasive treatment option with reportedly high technical and clinical success rates; however, B-mode EUS occasionally fails to depict the target lesion and its margins, particularly in cases where the target shows a heterogeneous echogenicity. In our case, EUS-TD was attempted for infected WON, but visualization using B-mode EUS imaging was poor. Thus, CH-EUS was performed to enhance the contrast between the targeted WON and its surrounding tissues. Immediately after injecting a sonographic contrast agent, WON and its margins were clearly identified as an avascular area and were punctured under CH-EUS guidance. CH-EUS enables the assessment of the microvasculature and hemodynamics of the target lesion in real time. It may also provide valuable information and could be a useful modality for EUS-TD to clearly visualize target lesions and their margins and to decisively puncture them, even when they could not be identified using B-mode EUS.

Contrast-enhanced (endoscopic) ultrasound and endoscopic ultrasound elastography in gastrointestinal stromal tumors

Background and Objectives:

Gastrointestinal stromal tumors (GISTs) represent the largest group of subepithelial tumors (SET) of the upper gastrointestinal (GI) tract. They may show malignant behavior, in contrast to other SET. Endoscopic ultrasound (EUS) is frequently used to characterize SET. With the introduction of contrast-enhanced ultrasound (CEUS) into EUS (CE-EUS), distinct enhancement patterns can be detected. In the presented study, the characteristic features of CE-EUS in GIST are analyzed and compared with those of other SET.

Materials and Methods:

Consecutive patients from four centers with SET of the upper and middle GI tract were included and received endoscopic or transcutaneous CEUS. The results were compared with EUS-guided tissue acquisition, forceps biopsy, or surgical resection.

Results:

Forty-two out of 62 (68%) patients had SET of the stomach, 17/62 (27%) of the small intestine, 2/62 (3%) of the esophagus, and 1/62 (2%) extraintestinal. Eighty-one percent underwent surgery. Leiomyoma was found in 5/62 (8%) and GIST in 57/62 patients (92%). Thirty-nine out of 57 (68%) patients had GIST lesions in the stomach, 17/57 (30%) had GIST of the small intestine, and 1/57 (2%) patients had extraintestinal GISTs. GIST size was 62.6 ± 42.1 (16–200) mm. Hyperenhancement had a sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 98%, 100%, 100%, 93%, and 98% for the diagnosis of GIST. Fifty out of 57 patients with GIST (88%) showed avascular areas in the center of the lesions.

Conclusion:

CE-EUS and CEUS show hyperenhancement and avascular areas in a high percentage of GIST but not in leiomyoma. Thus, GIST and leiomyoma can be discriminated accurately.

Assessing tumor vascularization as a potential biomarker of imatinib resistance in gastrointestinal stromal tumors by dynamic contrast-enhanced magnetic resonance imaging

BACKGROUND

Most metastatic gastrointestinal stromal tumors (GISTs) develop resistance to the first-line imatinib treatment. Recently, increased vessel density and angiogenic markers were reported in GISTs with a poor prognosis, suggesting that angiogenesis is implicated in GIST tumor progression and resistance. The purpose of this study was to investigate the relationship between tumor vasculature and imatinib resistance in different GIST mouse models using a noninvasive magnetic resonance imaging (MRI) functional approach.

METHODS

Immunodeficient mice (n = 8 for each cell line) were grafted with imatinib-sensitive (GIST882 and GIST-T1) and imatinib-resistant (GIST430) human cell lines. Dynamic contrast-enhanced MRI (DCE-MRI) was performed on GIST xenografts to quantify tumor vessel permeability (K ^trans) and vascular volume fraction (v _p). Microvessel density (MVD), permeability (mean dextran density, MDD), and angiogenic markers were evaluated by immunofluorescence and western blot assays.

RESULTS

Dynamic contrast-enhanced magnetic resonance imaging showed significantly increased vessel density (P < 0.0001) and permeability (P = 0.0002) in imatinib-resistant tumors compared to imatinib-sensitive ones. Strong positive correlations were observed between MRI estimates, K ^trans and v _p, and their related ex vivo values, MVD (r = 0.78 for K ^trans and r = 0.82 for v _p) and MDD (r = 0.77 for K ^trans and r = 0.94 for v _p). In addition, higher expression of vascular endothelial growth factor receptors (VEGFR2 and VEFGR3) was seen in GIST430.

CONCLUSIONS

Dynamic contrast-enhanced magnetic resonance imaging highlighted marked differences in tumor vasculature and microenvironment properties between imatinib-resistant and imatinib-sensitive GISTs, as also confirmed by ex vivo assays. These results provide new insights into the role that DCE-MRI could play in GIST characterization and response to GIST treatment. Validation studies are needed to confirm these findings.

The clinical impact of ultrasound contrast agents in EUS: a systematic review according to the levels of evidence

BACKGROUND AND AIMS

The use of contrast-harmonic EUS (CH-EUS) in routine clinical practice is increasing rapidly but is not yet standardized. We present the levels of evidence (LEs) found in the literature to put its clinical outcomes in the appropriate perspective.

METHODS

We conducted a systematic review of the available English-language articles. The LEs were stratified according to the Oxford Centre for Evidence-Based Medicine guidelines.

RESULTS

Overall, 210 articles were included and presented according to different pathologic conditions. For pancreatic solid neoplasms, the pooled sensitivity and specificity in the diagnosis of pancreatic carcinoma were very high (LE 1); quantitative analysis and guidance of FNA were reported as investigational research (LE 2-3). For pancreatic cystic lesions, the identification of neoplastic solid components as hyperenhanced lesions represented a promising application of CH-EUS (LE 2). For lymph nodes, CH-EUS increased the diagnostic yield of B-mode EUS for the detection of malignancy (LE 2). For submucosal tumors, CH-EUS seemed useful for differential diagnosis and risk stratification (LE 2-3). For other applications, differential diagnosis of gallbladder and vascular abnormalities by CH-EUS were reported (LE 2-3).

CONCLUSIONS

The LEs of CH-EUS in the literature have evolved from the initial descriptive studies to multicenter and prospective trials, and even meta-analyses. The differential diagnosis between benign and malignant lesions is the main field of application of CH-EUS. With regard to pancreatic solid neoplasms, the concomitant use of both CH-EUS and EUS-FNA may have additive value in increasing the overall accuracy by overcoming the false-negative results associated with each individual technique. Other applications are promising but still investigational.

Advances in endoscopic ultrasound imaging of colorectal diseases

The development of endoscopic ultrasound (EUS) has had a significant impact for patients with digestive diseases, enabling enhanced diagnostic and therapeutic procedures, with most of the available evidence focusing on upper gastrointestinal (GI) and pancreatico-biliary diseases. For the lower GI tract the main application of EUS has been in staging rectal cancer, as a complementary technique to other cross-sectional imaging methods. EUS can provide highly accurate in-depth assessments of tumour infiltration, performing best in the diagnosis of early rectal tumours. In the light of recent developments other EUS applications for colorectal diseases have been also envisaged and are currently under investigation, including beyond-rectum tumour staging by means of the newly developed forward-viewing radial array echoendoscope. Due to its high resolution, EUS might be also regarded as an ideal method for the evaluation of subepithelial lesions. Their differential diagnosis is possible by imaging the originating wall layer and the associated echostructure, and cytological and histological confirmation can be obtained through EUS-guided fine needle aspiration or trucut biopsy. However, reports on the use of EUS in colorectal subepithelial lesions are currently limited. EUS allows detailed examination of perirectal and perianal complications in Crohn’s disease and, as a safe and less expensive investigation, can be used to monitor therapeutic response of fistulae, which seems to improve outcomes and reduce the need for additional surgery. Furthermore, EUS image enhancement techniques, such as the use of contrast agents or elastography, have recently been evaluated for colorectal indications as well. Possible applications of contrast enhancement include the assessment of tumour angiogenesis in colorectal cancer, the monitoring of disease activity in inflammatory bowel disease based on quantification of bowel wall vascularization, and differentiating between benign and malignant subepithelial tumours. Recent reports suggest that EUS elastography enables highly accurate discrimination of colorectal adenocarcinomas from adenomas, while inflammatory bowel disease phenotypes can be distinguished based on the strain ratio calculation. Among EUS-guided therapies, the drainage of abdominal and pelvic collections has been regarded as a safe and effective procedure to be used as an alternative for the transcutaneous route, while the placing of fiducial markers under EUS guidance for targeted radiotherapy in rectal cancer or the use of contrast microbubbles as drug-delivery vehicles represent experimental therapeutic applications that could greatly impact the forthcoming management of patients with colorectal diseases, pending on further investigations.

Can contrast-enhanced harmonic endosonography predict malignancy risk in gastrointestinal subepithelial tumors?

Background and Objectives:

Contrast-enhanced harmonic endoscopic ultrasound (CEH-EUS) is a novel technology that can identify subepithelial tumors (SETs) by detecting the degree of enhancement, but whether CEH-EUS can predict the malignancy risk of gastrointestinal stromal tumors (GISTs) remains unclear. The aim of our study was to evaluate the diagnostic accuracy of CEH-EUS and its ability to discriminate among SETs and predict the malignancy risk of GISTs.

Materials and Methods:

We retrospectively included patients with suspected subepithelial lesions who underwent CEH-EUS preoperatively. Thirty-five patients with histologically proven GISTs and benign neoplasms were enrolled in the study. The images of CEH-EUS were categorized in accordance with microvasculature, parenchymal perfusion, and nonenhancing spots. The diagnostic performance of CEH-EUS was evaluated by comparing these findings with the histological diagnosis.

Results:

When we divided the enrolled patients into high- and low-grade malignancy and benign groups, nonenhancing spots on CEH-EUS were found more frequently in the high-grade malignancy group (63.6%), followed by the low-grade malignancy (46.7%) and benign groups (25.7%) (P = 0.022). However, based on the statistical validity of the CEH-EUS findings for the discrimination of SETs, the sensitivity was 53.8% for diagnostic performance and 63.6% for prediction of malignancy risk of GISTs.

Conclusions:

From our study results, it is unclear whether CEH-EUS alone has a diagnostic role in the discrimination of SETs and the prediction of malignancy risk of GISTs. Further studies with larger samples from multiple centers and use of other imaging analysis modalities are needed.

Role of contrast-enhanced harmonic endoscopic ultrasound in submucosal tumors

With the widespread use of endoscopy, gastrointestinal submucosal lesions are now more commonly discovered. Although endoscopic ultrasound (EUS) is superior to all other imaging techniques for the diagnosis of submucosal tumors (SMTs), it is still suboptimal for differentiating hypoechoic lesions arising from the fourth sonographic gastrointestinal wall layer, which encompass tumors with very different prognosis. EUS tissue acquisition has provided with the unique opportunity to obtain histological confirmation, but it is not accurate enough to evaluate the malignant potential of gastrointestinal stromal tumors (GISTs). In the last years, contrast-enhanced harmonic EUS (CH-EUS) emerged as a powerful imaging modality to assess the microperfusion patterns of pancreatic tumors. Based on the distinct microvascularity of malignant SMTs, it was hypothesized that CH-EUS might also assist in the differential diagnosis of SMTs. Preliminary experience in this field is now available and suggests CH-EUS as a performant modality to distinguish between benign SMTs and GISTs and to evaluate the malignant potential of GISTs. High expectations are also relied on CH-EUS for the monitoring of antiangiogenic treatments of GISTs and the evaluation of gastrointestinal neuroendocrine tumors (NETs).

Beyond standard therapy: drugs under investigation for the treatment of gastrointestinal stromal tumor

INTRODUCTION

Gastrointestinal stromal tumor (GIST) is the most common nonepithelial malignancy of the GI tract. With the discovery of KIT and later platelet-derived growth factor α (PDGFRA) gain-of-function mutations as factors in the pathogenesis of the disease, GIST was the quintessential model for targeted therapy. Despite the successful clinical use of imatinib mesylate, a selective receptor tyrosine kinase (RTK) inhibitor that targets KIT, PDGFRA and BCR-ABL, we still do not have treatment for the long-term control of advanced GIST.

AREAS COVERED

This review summarizes the drugs that are under investigation or have been assessed in trials for GIST treatment. The article focuses on their mechanisms of actions, the preclinical evidence of efficacy, and the clinical trials concerning safety and efficacy in humans.

EXPERT OPINION

It is known that KIT and PDGFRA mutations in GIST patients influence the response to treatment. This observation should be taken into consideration when investigating new drugs. RECIST was developed to help uniformly report efficacy trials in oncology. Despite the usefulness of this system, many questions are being addressed about its validity in evaluating the true efficacy of drugs knowing that new targeted therapies do not affect the tumor size as much as they halt progression and prolong survival.