Globally, gastric cancer remains the fifth most common cancer and third most common cause of cancer-related deaths. Intestinal-type gastric adenocarcinoma, the most common type of gastric cancer, develops from the progression of chronic atrophic gastritis to gastric intestinal metaplasia (GIM) to dysplasia before malignant transformation in a small minority of individuals. Multifocal atrophic gastritis and GIM often coexist and are both associated with an increased risk of intestinal-type gastric adenocarcinoma. GIM is generally considered to be the first irreversible mucosal stage in the stepwise progression to cancer, albeit with some mixed data. GIM is defined histologically by intestinalization of normal gastric epithelium in response to chronic injury, most often colonization with Helicobacter pylori (H. pylori), although other causes such as autoimmune gastritis are recognized. GIM can be further classified according to histologic subtype of the intestinal metaplastic tissue as “complete-type,” which has features of small intestinal epithelium, “incomplete-type,” which has features of colonic epithelium, and “mixed-type,” which has the features of both (1). Because of the slow sojourn time between mucosal stages, endoscopic surveillance offers the opportunity for earlier detection and potentially curative treatment of gastric neoplasia (i.e., dysplasia or cancer).
Despite the established association with increased gastric cancer risk, the management of GIM presents a dilemma for many gastroenterologists. In the United States (US), the overall pooled prevalence of GIM is 4.8% (95% confidence interval: 4.8%–4.9%) (2). However, the marked variability in prevalence must be emphasized because individual studies have demonstrated that GIM prevalence is significantly higher in certain subgroups, including some racial and ethnic minorities and current or former tobacco users, among others (2). Recently, the American Gastroenterological Association provided the first US guidelines focused on the role of endoscopic GIM surveillance for improving gastric cancer-related outcomes. Here, we detail our approach to the endoscopic surveillance of individuals diagnosed with GIM and highlight the importance of risk stratification. Specific recommendations for GIM surveillance intervals vary slightly among Western gastroenterological societies, and full details are provided elsewhere (3–6).
EVALUATE FOR AND ERADICATE H. PYLORI IN ALL INDIVIDUALS WITH GIM
Because H. pylori eradication reduces the risk of gastric cancer, all individuals with GIM should be evaluated and treated for active infection, followed by confirmation of eradication (6,7). If gastric biopsies are negative for H. pylori, we often perform an alternative test for H. pylori, such as urease breath test or H. pylori antigen stool test because H. pylori colonization of the gastric mucosa might be patchy and is often absent in areas of GIM. Medications that reduce the sensitivity of H. pylori testing should ideally be discontinued before testing. There is insufficient evidence to advocate for empiric H. pylori eradication therapy among patients with GIM in the absence of documented H. pylori infection (6,7).
PATIENT SELECTION FOR GIM SURVEILLANCE
Although GIM is associated with a baseline 0.16% annual risk of incident gastric cancer based on a comprehensive systematic review (7), there was insufficient high-quality evidence to unequivocally establish whether GIM surveillance vs no surveillance is associated with improvement in important patient outcomes, such as gastric cancer-related mortality. Some individuals with GIM may exceed this baseline risk, however, and risk determination depends on a number of factors (Table 1). Risk stratification is complicated by the paucity of evidence delineating the attributable risks for each of these factors separately among individuals with GIM; nevertheless, individuals generally could be categorized as high- vs low-risk for gastric cancer.
We advocate for a shared decision-making process regarding GIM surveillance and discuss the following with a patients diagnosed with GIM: (i) what is GIM?; (ii) what is their estimated risk of gastric cancer (high vs low) based on their known risk factors?; (iii) the uncertain benefits of endoscopic surveillance vs no surveillance for decreasing gastric cancer-related mortality, and (iv) the potential risks, cost, and inconvenience associated with endoscopic surveillance.
ENDOSCOPIC TECHNIQUES TO ENHANCE DETECTION OF GIM
In the United States, GIM is often diagnosed incidentally among individuals undergoing upper endoscopy for a variety of indications unrelated to gastric cancer screening. In such scenarios, it is imperative to adjudicate whether the index endoscopy was complete or of sufficient quality to adequately visualize the gastric mucosa. If not, it would be reasonable to consider a repeat examination to rule out suspicious lesions and to determine GIM extent.
We recommend that a careful inspection be performed using high-definition white light endoscopy (HD-WLE). The importance of applying general techniques to improve mucosal visibility, such as the use of defoaming and mucolytic agents and adequate air insufflation, as well as sufficient withdrawal time and photo-documentation, warrants particular emphasis (8–10). HD-WLE has been shown to have high specificity (>90%) for GIM, although still with suboptimal sensitivity (53%–75%) in previous studies (4). Conventional chromoendoscopy with the application of dyes such as indigo carmine, methylene blue, or acetic acid is associated with improved accuracy and sensitivity for GIM but extends procedural times and can be cumbersome. Image-enhancing technologies such as narrow band imaging (NBI) offer a unique advantage in these regards. We routinely use a combination of HD-WLE and NBI for GIM surveillance examinations based on multiple studies demonstrating improved GIM detection with adjunctive NBI use (11,12). GIM has a typical appearance on NBI that is characterized by bluish-white areas with an irregular mucosal pattern (Figure 1). For this reason, NBI-enhanced HD-WLE can be particularly useful when performing biopsies to determine GIM extent (see below) and allows for more “educated” biopsies. Often, the blue-white lines appear on the crests of the epithelial surface in GIM, classically referred to as the “light blue crest” sign, which is more evident on magnification endoscopy. Profound irregular mucosal pattern and architectural distortion is concerning for dysplasia. A detailed discussion of image-enhancing techniques for augmented endoscopic detection of GIM, particularly given the limited or lack of access to these modalities in the United States, is beyond the scope of this article; that said, we encourage interested practitioners to refer to the plethora of review articles and other illustrative resources on this topic.
BIOPSY PROTOCOL, HISTOLOGIC REPORTING, AND DOCUMENTATION
Endoscopic GIM surveillance should achieve 2 main goals: (i) evaluate for and rule out neoplasia and (ii) determine GIM extent and histologic subtype. Extensive GIM, defined as any involvement of the corpus, is associated with at least 2-fold increased risk of incident gastric cancer compared with limited GIM, defined as only antral involvement (+/− incisura) (7). If local expertise is available, we recommend pathologists perform histologic subtyping of GIM into complete vs incomplete because the latter is associated with a 3.3-fold higher risk of gastric cancer based on limited but consistent data (1). The Operative Link on Gastritis Assessment and Gastritis/Intestinal Metaplasia Assessment staging classifications integrate both the severity (mild, moderate, severe) and extent (antrum/incisura, body) of atrophic gastritis and GIM and range from stage I (low) to stage IV (high). Although the Operative Link on Gastritis Assessment/Operative Link on Gastritis/Intestinal Metaplasia Assessment staging systems are useful for prognosis, with advanced stages (stage III/IV) associated with higher risk of neoplastic progression (13), they are not used routinely in the United States. Regarding documentation, it is important to describe the appearance of the mucosa, including any abnormalities such as nodularity or any discrete lesions and the location and number of biopsies, both targeted and nontargeted.
GIM is often patchy and might not be endoscopically discernible on HD-WLE alone. The optimal number of nontargeted biopsies that balances diagnostic yield with procedural time and cost has not been defined. We recommend using the updated Sydney protocol for nontargeted biopsies which requires 5 biopsies (2 from the antrum at the lesser and greater curvature, 2 from the body at the lesser and greater curvature, and 1 from the incisura), preferably placed in separate jars (Figure 2) (14,15). If pathology cost dictated by the number of biopsy jars is a concern, we oftentimes place these nontargeted biopsies in 2 separate jars—that is, one jar labeled “body” and the other labeled “antrum/incisura.” Targeted biopsies using NBI should be obtained from suspicious mucosal lesions or concerning areas and placed in separately labeled jars. This approach has been shown to increase the yield of GIM detection (11).
The importance of GIM as a premalignant diagnosis is increasingly recognized in the United States, although there is still an unmet need to standardize the endoscopic GIM surveillance practices. The magnitude and pace of progress is limited by the dearth and heterogeneity of the literature, particularly when generalizing findings from populations with different gastric cancer incidence and risk factor profiles. As more data are generated, endoscopic surveillance protocols will undergo iterative modifications and become increasingly personalized. Regardless, adjunctive risk reduction interventions, patient selection based on appropriate stratification by gastric cancer risk, and adequate mucosal visualization and assessment will remain foundational elements of GIM management and surveillance.
CONFLICTS OF INTEREST
Guarantor of the article: Shailja C. Shah, MD, MPH.
Specific author contributions: S.C.S. drafted the manuscript; all authors edited the manuscript and provided important intellectual content; D.L. provided the images.
Financial support: None to report.
Potential competing interests: None to report.
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