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Background Since its introduction in the early 1990s, minimally invasive gastro-oesophageal surgery for cancer has been growing in popularity. Despite this, published evidence on this type of technique is weak and its role in the management of gastric and oesophageal cancer remains controversial. Aims The aim of this thesis was to test the hypothesis that: minimally invasive gastro- oesophageal cancer surgery has superior outcomes compared to control studies of conventional open surgery; but current studies are methodologically inadequate to confirm this. Methods The first study (chapter 3) is a systematic review of the literature on minimally invasive gastro-oesophageal cancer surgery, outlining the differences between literature published in Eastern and Western countries. The following 3 chapters outline and use a phase II surgical study to obtain data on minimally invasive gastro-oesophageal cancer (MIGOCS.) The MIGOCS group was set up in 2005 amongst UK surgeons. An online database was developed to enable data collection and comprises 5 sections: demographics; pre-operative staging and assessment; surgical intervention; post-operative course; pathology and clinical outcome. The first study is retrospective collecting data up to December 2006; the second study is prospective with data obtained between December 2006- July 2008 from centres around the UK utilising the MIGOCS database. Chapter 7 involves analysis of the learning curve in laparoscopic gastro-oesophageal cancer surgery using CUSUM (continuous surveillance monitoring) assessment. By studying operative time at each centre, improvement or deterioration in quality were detected. Results The systematic review of minimally invasive gastro-oesophageal surgery consists in the majority of case reports, with no randomised controlled trials of oesophagectomies and 4 (low quality) randomised controlled trials of gastrectomies. It demonstrates a mortality and morbidity of 2.3% and 46.2% respectively for oesophagectomies; 0.1% and 12.7% respectively for gastrectomies. Data from this review suggests that the minimally invasive approach is beneficial compared to open surgery in terms of reduced mortality, respiratory complications, blood loss and quicker return to a good quality of life (but not reduced hospital stay as expected.) There are currently 60 MIGOCS member consultant surgeons from over 40 UK centres. The retrospective study obtained data from 7 UK centres with an overall mortality and morbidity of 6.0% and 57% respectively for oesophagectomies and 7.7% and 13% respectively for gastrectomies. The prospective study collected data from 7 UK centres, comprising a total of 258 minimally invasive oesophagectomies and 33 minimally invasive gastrectomies. Overall mortality and morbidity were 2.5% and 56.6% respectively for oesophagectomies and 10.8% and 27.3% respectively for gastrectomies. CUSUM analysis varied considerably between centres. The two larger volume centres however demonstrated an improvement in their operative time with experience, with a possible pateau at around 30 procedures. Conclusions Published data suggests that the minimally invasive approach to gastro-oesophageal cancer has advantages over conventional open surgery. Data collected in this thesis does not overwhelmingly support published evidence, but does demonstrate that this technique is both safe and feasible even during the early part of a surgeon's learning curve. It is the first study to provide an insight into outcomes of this type of surgery in a multicentre setting in the UK; and has made progress towards a randomised controlled trial.

The incidence of oesophageal adenocarcinoma (OA) has increased exponentially in the western world over the past few decades. Barrett's oesophagus (BO) is a well known precursor of OA with a risk approximately 20 times more than that of background population. Regular endoscopic surveillance in patients with BO is recommended by most of the national gastroenterological societies. The advantage of Barrett's surveillance is to identify early subtle lesions which could then be managed early to avoid symptomatic and advanced cancers. The detection of such early lesions are challenging as they could be flat and inconspicuous on routine endoscopic examination. In the absence of any lesions, four quadrant biopsies every 1-2 cm of the whole length of Barrett's oesophagus is advised. This technique would map only 5-10% of the surface area of Barrett's segment and hence it is associated with significant sampling error. The improvement in electronics over the past decade has led to the production of endoscopes with better charged coupled devices and image enhancement techniques by altering the spectrum of light. This thesis examines the role of multi modal imaging in Barrett's oesophagus with a focus on detecting dysplasia and early cancer (EC). Firstly, the role of high definition (HD) imaging in routine clinical setting was studied using data from patients who have undergone Barrett's· surveillance. The yield of dysplasia by HD endoscopy was compared to standard definition (SD) endoscopy in this study. The role of narrow band imaging (NBI) with magnification in characterising abnormal lesions detected during BO surveillance was evaluated by performing a meta- analysis of clinical studies. The role of autofluorescence imaging (AFI) in Barrett's oesophagus was examined in detail with a view to understand the biological basis of autofluorescence and to improve the specificity of this technique as it is associated with significant false positive results in clinical studies. A meta-analysis was performed to identify whether AFI has a clinical advantage over white light endoscopy in detecting Barrett's dysplasia and the inter-observer reliability of this technology was studied using AFI expert and AFI non-expert endoscopists. An objective method of measuring the autofluorescence intensity was proposed as a ratio of the red to the green colour tone (AF ratio) of the area of interest. When the AF ratio of the lesion was divided by the AF ratio of the background mucosa, an AF index is obtained. A pilot study was performed to identify a cut-off value of AF index to differentiate high grade dysplasia (HGD) and EC from non-dysplastic BO. Finally, the biological basis of AF intensity was examined using APCmin mouse colonic models. This study looked into the AF ratio of the colonic mucosal lesions and correlated it with the amount of collagen and elastin in the submucosal tissue. Collagen and elastin are known to be the strongest fluorophores of the gastrointestinal tract and the question addressed is whether the low AF intensity associated with dysplastic lesions is due to the thickening of mucosa or to a reduction of collagen and elastin.

The UK has experienced an increase in the incidence of oesophageal adenocarcinoma (OAC) in recent years. The prognosis for patients with OAC remains poor with currently available treatments prompting a search for alternative ‘chemopreventive’ treatments that inhibit oesophageal carcinogenesis. Both non-steroidal anti-inflammatory drugs (NSAIDS) and flavonoids are associated with a significant risk reduction for developing OAC in epidemiological studies. The aim of this study was to validate Levrat’s surgical model of OAC in the rat, and assess the chemopreventive effects of the NSAID aspirin, and the flavonoid quercetin on the development of OAC in the validated rat model. METHODS: Levrat’s model was validated in a time course experiment. Morphological and molecular events occurring in the distal oesophagus during disease progression were determined and compared to human disease. The effect of aspirin and quercetin on disease initiation and progression was determined by commencing treatment either before the onset of reflux, or 4-weeks afterwards. The incidence of Barrett’s oesophagus (BO) and OAC within each group was determined, along with methylation levels of the ESR-1, p16 and HPP1 gene promoter regions. RESULTS: The morphological and molecular changes in the distal oesophagus of the rat model are broadly consistent with those reported in human disease. The incidence of OAC was significantly lower in aspirin treated rats. A non-significant reduction in incidence of OAC was observed with quercetin treatment. Timing of treatment with regard to onset of reflux had no significant effect on OAC development in either treatment group. Neither treatment significantly effected methylation levels within the gene promoters examined. CONCLUSION: Use of Levrat’s model as a model of human OAC seems justified. Aspirin inhibits development of oesophageal adenocarcinoma induced by reflux in this rat model. No additional reduction in cancer incidence is observed if treatment is commenced prior to inception of reflux disease.

The incidence of neoplasia at the gastroesophageal junction has increased markedly over the past 20 years, but the mutagen responsible for this remains unknown. Human saliva contains substantial quantities of nitrite and is the main source of nitrite entering the stomach. It is derived from the enterosalivary recirculation of dietary nitrate and its reduction by buccal bacteria. Carcinogenic N-nitrosocompounds may be formed from the nitrite in swallowed saliva by bacterially-catalysed nitrosation in the achlorhydric stomach or acid-catalysed nitrosation in the healthy acid secreting stomach. Protection against luminal acid-catalysed nitrosation is provided by the ascorbic acid content of human gastric juice which reduces nitrite to nitric oxide (NO). A high luminal concentration of NO generated from salivary nitrite has been shown at the gastroesophageal junction. A bench top model has been developed to explore the chemistry occurring in an aqueous phase, representing the lumen at the gastroesophageal junction, after the addition of nitrite. Within this model an adjacent lipid phase has been created. The lipid phase represents the adjacent mucosa to the lumen or the dietary fat shown to sit within the fundus of the stomach. In this two-phase model, addition of physiological concentrations of nitrite to an acidic aqueous phase in the absence of ascorbic acid generated nitrosative stress within the aqueous phase. The addition of physiological concentrations of ascorbic acid to the aqueous phase prevents nitrosative stress within the aqueous phase but in so doing generates nitrosative stress within the lipid phase. This can be explained by the ascorbic acid converting the salivary nitrite to NO which diffuses into the lipid phase and there reacts with O2 to form the nitrosating species N2O3. The bench top model has been developed further to include the lipid antioxidants, α-tocopherol, β-carotene and BHT. All three of these antioxidants are effective in inhibiting nitrosative stress within the lipid phase. The concentration of α-tocopherol required to inhibit nitrosation is less than would be expected from the reaction equation. A possible explanation for this is that ascorbic acid recycles the active antioxidant α-tocopherol from its reduced form. Further studies to support recycling of α-tocopherol by ascorbic acid are presented within this thesis. The design of a model used in vivo to assess for nitrosative stress is discussed. The model consisted of a hydrophobic silastic tubing containing a secondary amine at a neutral pH. The hydrophobic membrane that the tubing is composed of allowed the passage of gaseous NO. Human studies in healthy volunteers were performed using the silastic tubing. The data presented shows that after a nitrate rich drink there is significantly more nitrosative stress within the upper gastrointestinal tract and this is particularly the case in the first part of the stomach where salivary nitrite meets acidic gastric juice containing ascorbic acid. Finally, the studies explore directly measuring nitrosative stress in biopsy samples from humans and rats. As nitrite has been shown previously to be a marker of nitrosative stress in bench top models biopsy samples were assessed for nitrite and nitrate concentrations. Methods for assessing nitrite and nitrate concentrations within biopsy samples from the upper gastrointestinal tract are discussed, as nitrite and nitrate have not been analysed from this region previously. Thereafter, upper gastrointestinal biopsy samples from healthy human subjects were analysed after a control drink and a drink rich in nitrate. The studies presented show that biopsy nitrate and nitrite was higher in samples taken from the proximal stomach as compared to the oesophagus and distal stomach. This suggests that there is more nitrosative stress in the biopsies from the same area as where NO is generated after a nitrate meal. Together the data presented supports a novel mechanism for N-nitrosation in the upper gastrointestinal tract of a healthy subject. The N-nitrosation is maximal where swallowed salivary nitrite from dietary nitrate meets acidic gastric juice containing the aqueous antioxidant ascorbic acid.

Le développement du traitement endoscopique des états précancéreux et cancers superficiels de l’œsophage, qui constitue une option alternative à faible risque opératoire au traitement chirurgical, se heurte à la problématique de la cicatrisation œsophagienne. En effet, les résections étendues de la muqueuse œsophagienne se compliquent de sténoses cicatricielles réfractaires. Les voies de prévention de la sténose œsophagienne impliquent la protection de la plaie, l’opposition aux mécanismes de l’inflammation et de la fibrose, la promotion de la réparation épithéliale, ou encore l’application d’une contrainte mécanique sur la paroi de l’œsophage au cours de la cicatrisation. Au cours d’un premier travail, nous avons évalué, sur un modèle porcin de sténose œsophagienne post-endoscopique que nous avons développé, l’apport de la membrane amniotique humaine (MAH) en tant qu’agent protecteur, mais aussi anti-fibrosant, régénératif, appliqué au moyen de prothèses œsophagiennes. Nous avons mis en évidence un effet de la MAH à J14 en termes de taux de sténose, cependant transitoire en raison du manque de stabilité des prothèses œsophagiennes et de la dégradation de la MAH dans l’œsophage. Au cours d’un second travail, nous avons évalué sur le même modèle l’apport d’une poudre hémostatique minérale appliquée de façon itérative sur la zone de résection au cours de la première semaine. Ce traitement a permis d’améliorer significativement les paramètres histologiques (épaisseur du tissu de granulation, de la fibrose, longueur du néoépithélium) et biologiques (taux sérique de TGF-β) de la cicatrisation œsophagienne, cependant sans traduction sur le taux de sténose œsophagienne à J14. Au cours d’un troisième travail, nous avons évalué une matrice protéique formée d’un peptide autoassemblé (SAP) pour la couverture de la plaie œsophagienne, toujours dans le même modèle. Ce traitement a permis de diviser par deux le taux de sténose à J14, sans cependant que les résultats soient durables, 100% des animaux ayant développé des sténoses à J28. Au cours d’un quatrième travail, nous avons évalué chez 40 patients la faisabilité et les performances de la réalisation en un seul temps endoscopique d’une résection endoscopique par mucosectomie d’une lésion suspecte d’adénocarcinome, et de l’ablation par radiofréquence de l’œsophage de Barrett résiduel. Nous avons observé une bonne efficacité de cette approche, permettant une procédure en un seul temps endoscopique chez près de la moitié des patients, et des taux d’éradication de la néoplasie et de la métaplasie intestinale de 95% après 19 mois de suivi. Cependant, cette approche était limitée par un taux de sténose de 33%. Au cours d’un cinquième travail, nous avons étudié rétrospectivement chez 35 patients les résultats de la dissection sous-muqueuse œsophagienne (ESD) dans le traitement de l’adénocarcinome œsophagien. Les résultats, avec un taux de résection R0 de 72% se réduisant à 66% de résection curative en tenant compte des facteurs histopronostiques défavorables, suggèrent qu’une amélioration de l’endoscopie diagnostique était nécessaire afin de mieux sélectionner les patients pouvant bénéficier de ce traitement. Le taux de sténoses cicatricielles de 6% était en revanche modéré dans cette série d’exérèses généralement non circulaires laissant souvent en place une muqueuse dysplasique. L’ensemble de ces résultats suggère que la problématique de la sténose cicatricielle reste majeure dans la résection endoscopique des cancers superficiels de l’œsophage. Les approches protectrices de prévention de la sténose sont limitées par le manque de stabilité des produits employés sur la plaie œsophagienne. Des travaux mécanistiques sont nécessaires, afin de développer des inhibiteurs pharmacologiques spécifiques de la fibrose œsophagienne. / No abstract