CHAPTER 6 MALIGNANT CONDITIONS INVOLVING THE OESOPHAGUS, STOMACH, SMALL INTESTINE, GALL BLADDER AND BILE DUCT
OESOPHAGOGASTRIC CANCERS
Despite a marked decline in fundal and distal tumours, there is a rising incidence of adenocarcinomas of the gastro-oesophageal junction and gastric cardia, particularly in Western nations, and predominantly in males. Comparatively high rates of this tumour are evident for the United Kingdom/Ireland, northern Europe, Australia and New Zealand, China and North America. The increase in incidence of cardia lesions has been associated with parallel increases for adenocarcinomas of the lower oesophagus, where hyperacidity, reflux oesophagitis, Barrett’s oesophagus and obesity have been proposed as likely risk factors. This may imply that there are, in fact, two diseases differing from each other in epidemiology, aetiology, pathology and clinical expression. It is important to distinguish cardia and lower-third oesophageal adenocarcinoma from gastric cancer invading the lower third of the oesophagus, as treatment options may vary.
Risk factors
Gastric
Precursors of gastric cancer include chronic gastritis (autoimmune and acquired), intestinal metaplasia/dysplasia, gastric polyps (adenomatous polyps, rare in hyperplastic polyps) previous gastrectomy (>15 y post resection), pernicious anaemia and, most importantly, Helicobacter pylori infection. Infection with H. pylori induces chronic gastritis. Whether treatment of H. pylori infection will diminish the risk of gastric cancer is currently under investigation.
Investigations
Computed tomography (CT) scanning
Of value in oesophageal cancer for the detection of distant metastases, particularly liver and pulmonary metastases. It can detect tracheal or bronchial invasion in up to 90% of cases, and the identification of pleural and pericardial involvement is similar. It is less accurate in the detection of nodal metastases (70% accuracy) and assessment of the cardio-oesophageal area, and the presence of diaphragmatic involvement is less secure with CT scanning. In gastric cancer, overall detection rates of the primary tumour approach 90%, but requires a high-resolution scanner, and distension of the stomach with water and contrast. CT has an accuracy of 70% in detection of nodal metastases, and the detection of distant metastases is similar to oesophageal cancer.
Endoscopic ultrasound (EUS)
A useful tool in the preoperative staging of both oesophageal and gastric cancers, and its use provides superior results to CT in the local staging of these tumours. EUS can identify involved lymph nodes in up to 90% of cases, but is less accurate in early stage disease. EUS has a central role in the initial anatomic staging of oesophageal cancer because of its high accuracy in determining the extent of locoregional disease. EUS is inaccurate for staging after radiation therapy and chemotherapy, but can be useful in assessing treatment response. For initial anatomic staging, EUS results have consistently shown more than 80% accuracy compared with surgical pathology for depth of tumour invasion. Accuracy increases with higher stage, and is >90% for T3 cancer. EUS results have shown accuracy in the range of 75% for initial staging of regional lymph nodes. EUS has been invariably more accurate than computed tomography for tumour (T) and lymph node (N) staging. EUS is limited for staging distant metastases (M), and therefore EUS is usually performed after assessment for distant metastases by CT scanning or positron emission tomography. Pathologic staging can be achieved at EUS using fine-needle aspiration (FNA) to obtain cytology from suspect lymph nodes. FNA has had greatest efficacy in confirming coeliac axis lymph node metastases with more than 90% accuracy. EUS is inaccurate for staging after radiation and chemotherapy because of its inability to distinguish inflammation and fibrosis from residual cancer, but a decrease in tumour cross-sectional area or diameter of more than 50% has been found to correlate with treatment response. Stricture due to tumour precludes full assessment of tumour size and nodal status, and dilatation to allow passage of the probe results in a high perforation rate. EUS offers the best preoperative local gastric cancer staging, with accuracies in T and N staging of approximately 78% and 70%, respectively. Although EUS is not suitable for diagnosing distant metastases, it may be more useful in detecting ascites due to the close proximity to the peritoneum.