The Metaplastic Mosaic of Barrett's Oesophagus

Virchows Archiv (2018) 472:43–54 https://doi.org/10.1007/s00428-018-2317-1 INVITED ANNUAL REVIEW ISSUE The metaplastic mosaic of Barrett’s oesophagus Sujata Biswas1 & Michael Quante2 & Simon Leedham1 & Marnix Jansen3,4 Received: 29 November 2017 /Revised: 1 December 2017 /Accepted: 5 December 2017 /Published online: 3 March 2018 # The Author(s) 2018. This article is an open access publication Abstract Barrett’s oesophagus surveillance biopsies represent a significant share of the daily workload for a busy histopathology department. Given the emphasis on endoscopic detection and dysplasia grading, it is easy to forget that the benefits of these screening programs remain unproven. The majority of patients are at low risk of progression to oesophageal adenocarcinoma, and periodic surveillance of these patients is burdensome and costly. Here, we investigate the parallels in the development of Barrett’s oesophagus and other scenarios of wound healing in the intestine. There is now increased recognition of the full range of glandular phenotypes that can be found in patients’ surveillance biopsies, and emerging evidence suggests parallel pathways to oesophageal adenocarcinoma. Greater understanding of the conditions that favour progression to cancer in the distal oesophagus will allow us to focus resources on patients at increased risk. Keywords Metaplasia . Barrett’soesophagus . Inflammation . Lineage tracing Introduction oesophageal adenocarcinoma has increased by about 5% an- nually since the 1970s [3]. The majority of oesophageal adenocarcinoma patients still present at advanced stages of disease, and overall 5-year survival consequently remains poor at BIt is hard to make a patient without complaints feel around 15%. Given these figures, there is a clear and immi- better.^ nent need for diagnostic tools that will help us find patients at increased risk. Oesophageal adenocarcinoma surveillance (‘Barrett’sscreen- Barrett’s oesophagus (BO) is the most proximate risk factor ing’) encapsulates some of the best and some of the worst that for oesophageal adenocarcinoma development. The condition early cancer detection programs have to offer. The initiation of is defined as the metaplastic replacement of squamous epithe- these surveillance programs has been prompted by the in- lium with columnar epithelium in the distal oesophagus in crease in oesophageal adenocarcinoma incidence over the last response to acid-biliary reflux. Importantly, the increase in 40 years [1, 2]. Although squamous cell carcinoma remains oesophageal adenocarcinoma incidence is paralleled by an the predominant malignant condition affecting the oesopha- apparent rise in BO prevalence, further supporting the concept gus in many developing nations around the globe, in the west, that BO is the key precursor lesion to oesophageal adenocarcinoma [4]. However, determining the exact population prevalence of BO is less straightforward than it may seem at first. This is principally because heartburn complaints are common * Simon Leedham [email protected] in the general population and there is only a weak association between the reported presence of heartburn and the develop- * Marnix Jansen [email protected] ment of BO [5]. An inherited predisposition plays some part in Barrett’s development as indicated by GWAS studies that 1 Nuffield Department of Medicine, University of Oxford, Oxford, UK compared Barrett’s patients and normal controls. These stud- 2 II. Medizinische Klinik, Klinikum Rechts der Isar, Technische ies have revealed that BO occurs more commonly in individ- Universität München, Munich, Germany uals carrying one (or more) of a small set of genetic risk 3 UCL Cancer Institute, London, UK polymorphisms [6]. This suggests that an inherited predisposition can determine the tissue response to acid-biliary reflux. 4 University College London Hospital, London, UK 44 Virchows Arch (2018) 472:43–54 Intriguingly, some of these polymorphisms are found in genes the group of Doug Corley on the efficacy of Barrett’ssurveil- involved in oesophageal embryonic development. This illus- lance endoscopy, the authors showed that there was no asso- trates the complex multifactorial aetiology of Barrett’sdevel- ciation between exposure to upper gastro-intestinal endoscopy opment, wherein an environmental factor precipitates the de- and oesophageal cancer death [14]. Indeed, patients who had velopment of a precursor lesion in individuals carrying genetic died from oesophageal adenocarcinoma were just as likely to risk alleles. have undergone surveillance endoscopy as control patients. A further factor that complicates the assessment of the true Now, because this was a community-based study, there were population prevalence of BO is the simple fact that the formal many confounders the authors could not control for. However, definition of the condition varies between nations. The the absence of any protective effect of endoscopy is stunning. European Society for Gastrointestinal Endoscopy (ESGE) The evidence in favour of surveillance endoscopy comes and American Gastroenterology Association (AGA) guide- mainly from case-control studies wherein Barrett’s patients lines both require that intestinal metaplasia be documented included in screening programs were compared with appro- on oesophageal biopsy, because intestinal metaplasia is seen priate controls. As might be expected, inclusion in a screening as a sine qua non for cancer progression [7]. By contrast, the program correlates with detection of cancer at earlier stages, British Society for Gastroenterology (BSG) guidelines stipu- which is less likely to have spread beyond the oesophagus, late that BO is primarily an endoscopic diagnosis [8]. and this translates to longer overall survival times for patients Although this difference may seem trivial, in practice, this who were diagnosed with oesophageal adenocarcinoma may mean that a given patient is eligible for Barrett’ssurveil- whilst on a surveillance program [15]. However, these uncon- lance in London, whereas this same patient, after relocating to trolled studies are susceptible to many biases, including Amsterdam, would no longer be eligible for surveillance. length-time and lead-time biases. For these reasons, population estimates of BO vary between In short, there is no direct evidence that Barrett’s surveillance 1and5%[9]. Even if the true estimate is closer to the lower on balance reduces oesophageal cancer mortality. Much of this bound, then there is still a large reservoir of individuals at some uncertainty likely relates to the fact that BO remains an risk of oesophageal adenocarcinoma. However, despite the underdiagnosed condition. Indeed, most patients with newly di- aforementioned relative annual increase in oesophageal adeno- agnosed oesophageal adenocarcinoma have no history of either carcinoma incidence, the absolute risk remains low and retro- BO or heartburn complaints [3]. The clinical return and cost- spective population-based studies have demonstrated a progres- benefit to society of Barrett’s surveillance have, for all of these sion rate of around 0.10–0.13% per patient per year [10, 11]. In reasons, come under increased scrutiny. It is hoped that trials such other words, within a random sample of 50,000 individuals, as the British BOSS (Barrett’s Oesophagus Surveillance Study) around 500 of these individuals will have BO (1% prevalence), and the German BarrettNET studies, wherein a total of over 5000 and of these 500 individuals, only 1 will develop oesophageal Barrett’s patients will be followed for over 10 years to investigate adenocarcinoma in a given year. These figures indicate that the all-cause and disease-specific mortality between patients who majority of patients with BO have a long-term benign condition. have been randomly allocated to two-year endoscopic surveil- In fact, because of shared co-morbidities (male gender, obesity), lance or conservative clinical follow-up, will finally provide us the absolute risk of dying of cardiovascular disease is much with guidance on this issue. However, the trial’s sample size and greater than the risk of dying of oesophageal adenocarcinoma length of follow-up are a clear indication of the complexity and in patients with BO [12]. Even if we put important consider- magnitude of this endeavour. ations of finite resource allocation and healthcare spending aside, Pathologists play a significant role in this debate over the given these numbers, we should carefully consider whether in- efficacy and efficiency of Barrett’s surveillance. A significant clusion of patients in Barrett’s surveillance programs does in- share of the daily workload for a busy department can consist deed strike a fair balance between the protection afforded by of oesophageal screening biopsies. At the same time, pres- early endoscopic diagnosis and the risks and negative quality- sures on the pathology workforce have never been higher with of-life impact of cancer screening [13]. staffing levels not increasing at the same level as the demand [16]. Given the minimal reported benefit of current surveillance practices for oesophageal adenocarcinoma, it is clear Lack of evidence in favour of Barrett’s that we must find ways that allow patient selection with great- surveillance er precision and at reduced cost [17, 18]. What then is the evidence that Barrett’ssurveillancereduces oesophageal cancer mortality? Surprisingly, the evidence for The Barrett’smetaplasticmosaic this is thin at best. In fact, some studies have concluded

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