ABSTRACT
Introduction Gastric cancers are a common sequel to a peptic ulcer, and thus show a similar range of risk factors. Nearly a million cases of gastric cancer are diagnosed world-wide each year. Moreover, gastric neoplasms are the second most common cause of cancer deaths1 and once a gastric tumour has been diagnosed, the prognosis is poor.2 Squamous and adenomatous oesophageal cancers have a lower annual incidence, varying from 1-5 per 100,000 people in different countries.3,4 Often, tumours of the oesophagus are preceded by a history of oesophageal reflux (see Chapter 2). Again, once an oesophageal cancer has been diagnosed, the prognosis is very poor. Malignant tumours of the duodenum account for only 0.3% of all gastro-intestinal tumours,5 and there does not seem to be any information as to how their prevalence may be affected by physical activity. Thus, they will not be discussed further in the present chapter. Until around 2013, physical activity was commonly regarded as having little impact upon the risk of developing either gastric or oesophageal cancers. An article published in 2014 suggested that only 5 of the 12 available reports had found an inverse relationship between physical activity and oesophageal cancer, and the same was true for only 8 of 21 studies of gastric cancer.6 However, in the last four years, five systematic reviews and meta-analyses have dramatically changed this negative viewpoint. All 5 of the recent reports have presented evidence that regular physical activity is associated with a 20-30% decrease in the risk of gastro-oesophageal adenocarcinomas in humans that is statistically and clinically significant (see Table 5.1).
