Early detection and determinants of esophageal cancer

Abstract

Barrett’s esophagus (BE) is a premalignant condition of the esophagus and characterized by the metaplastic replacement of esophageal squamous epithelium by specialized intestinal-type columnar epithelium. A BE diagnosis is based on endoscopy and histological examination of biopsies taken during endoscopy. Patients with BE have an increased risk of developing esophageal adenocarcinoma (EAC), they are therefore advised to participate in a surveillance program, in order to detect progression towards EAC at an early and hopefully curable stage. In this thesis we determined the effect of patient and tumor characteristics on diagnosis, treatment and survival of esophageal cancer (EC) and performed an exploratory study to find a non-invasive test to diagnose BE and EAC. In the first part of this thesis, we found that EC incidence increased between 1993 and 2009, with a higher increase in EAC compared to esophageal squamous cell carcinoma (ESCC). In addition, we found that patients with a low socio-economic status (SES) were diagnosed with EAC or ESCC at an older age, with a more advanced tumor stage and they had more comorbidities compared to high SES patients. After adjustment for comorbidities, tumor stage and age, patients with a high SES were more likely to undergo a curative treatment. It can be concluded that SES is an important factor in the treatment choice of EC. This is a remarkable finding since healthcare is equally accessible to the Dutch population. Furthermore, we determined that short-term survival was inversely associated with an unknown T-stage, a positive lymph node status, chemoradiation therapy and presence of one or more comorbidities. In contrast the histological subtype EAC was associated with positive effect on short-term survival. Medium- and long-term survival were inversely affected by positive lymph nodes and chemoradiation therapy, while female gender and neoadjuvant therapy were positive prognostic factors. Acid and bile salts are suggested to play a predominant role during BE development. An in vitro model in which this process can be studied would therefore be useful. In the second part of this thesis, we summarized the available studies on this topic and we concluded that due to the high variability in reported methods (cell lines, types and concentrations of bile salts, pH, incubation periods and outcome parameters), it is difficult to find the most effective in vitro set-up. Several miRNAs, for example miRNA-143, -145, -192 and -194, have been reported to be highly expressed in BE tissue, however how this is regulated is largely unknown. We showed that, in addition to factors known to be highly expressed in BE tissue, miRNA-143, -145, -192 and -194 are upregulated in a squamous epithelium cell line upon incubation with an acidic bile mixture. In addition, inhibition of the NF-κB pathway resulted in significantly decreased miRNA-143, -192, -194 expression. Taken together, these results suggest that upregulation of BE-specific miRNAs by acidic bile may be an early event in the transition of SQ epithelium to BE and that their expression is partly regulated by the NF-κB pathway.

In the last part of this thesis, we determined the expression of circulating miRNAs in healthy controls, BE patients and EAC patients. Six miRNAs were selected for further validation in a larger group of patients and healthy controls. Our results suggest that the analysis of circulating miRNAs may be useful for the diagnosis of BE and EAC. Therefore, miRNA-95, -133a, -136, -194, -382 and -451 can potentially function as non-invasive molecular markers for BE and EAC screening.