Stomach and Oesophageal Cancer Study (SOCS)

OBJECTIVES:

• To set up a population-based gastric and esophageal cancer cohort with comprehensive epidemiological, clinical, and pathological data in order to identify novel genetic and environmental risk factors for these cancers using an association study design.
• To establish a blood-based epidemiological resource with parallel tumor samples on a population-based series of gastric and esophageal cancer cases.
• Compare any differences in genetic susceptibility genes according to the site of esophago-gastric cancer (e.g., distal gastric, proximal gastric, or junctional and esophageal tumors) and the histopathological sub-type.
• Test existing molecular hypotheses and determine whether common genetic variants in candidate genes predispose to gastric and esophageal cancer by comparing the frequency of variants in cancer patients with that in controls.
• Generate new hypotheses of genetic and certain environmental determinants, explore the potential impact on cancer disease risk of a range of environmental factors that can be measured in plasma (e.g., antibodies to various infective agents, markers of systemic inflammation, markers of oxidation), and examine gene-environment interactions.
• Refine our understanding of risk factors that are identified (e.g.,chronic Helicobacter pylori infection and smoking) and examine how these interact with genetic determinants of disease.
• Define the proportion of gastric cancer incidence attributable to mutations in known predisposing genes, such as E-cadherin.
• Obtain data on molecular profiles of tumors (mostly paraffin-embedded, rarely frozen) using dense array technologies, therefore enabling studies of the interaction between germline polymorphisms and tumor somatic genotype upon tumor behavior, response to treatment, and patient outcome.

OUTLINE: This is a multicenter study.

Patients and healthy controls complete an epidemiological questionnaire, provide a blood sample for plasma and genetic analyses, and may also provide a saliva sample. Tumor samples (in the form of paraffin block material or, in rare cases, frozen) may also be obtained from the hospital where the patient underwent surgery.

White blood cells are assayed for DNA/RNA isolation to look at genetic variants. DNA is extracted from saliva to look at genetic variants. Plasma/serum samples are analyzed to look at proteins and serological markers. Tumor samples are used to review the histology type. Nucleic acids are extracted from tumor sample sections; retrieval of a small (0.6 mm) core from each section is used to construct a tissue microarray which are be analyzed by immunohistochemistry and FISH.