Chapter 1 - Epidemiology, risk factors and pathogenesis
Summary: Epidemiology, risk factors and pathogenesis
- Taken together, the cancers of the intestinal tract are the most frequent tumours in humans, accounting for around one quarter of all cancer cases and almost one third of all cancer-related deaths. ~50% of these tumours are CRCs
- Except for CRC, with a 5-year survival of 60%, the remainder of GI tumours have a poor prognosis, the worst of which is pancreatic cancer, with 5-year survival <10%
- There are extreme geographical differences in the incidence of OC (more than for any other tumour). Incidence rates vary globally by more than 15-fold in men and almost 20-fold in women
- Smoking, alcohol, low fruit and vegetable intake and low income explain almost 99% of the attributable risk for OSCC in the USA and are strong risk factors in European countries, but tobacco and alcohol are weak risk factors in the highest risk areas of the world (Asian OC belt), where the aetiology of OSCC remains speculative
- H. pylori is the most common cause of non-cardia GC, though why H. pylori causes GC in only a minority of those infected remains unknown
- Given that GC is a multi-step process, the identification of patients with preneoplastic lesions with a high risk of progression and their periodic endoscopic surveillance represents the most effective method of early GC diagnosis
- There has been a substantial increase in the incidence of CRC in people <50 years old in several high-income countries. However, further studies are needed to establish the causes of this rising incidence and identify potential preventive and early-detection strategies
- CRC may be considered as a lifestyle disease: its risk is higher in countries with a diet high in calories and animal fat and a largely sedentary population with increased levels of overweight and obesity. However, there is still a lack of precise knowledge as to how multiple factors interact and contribute to risk
- Pancreatic cancer has one of the poorest prognoses among the major types of GI tumours. The most clearly established modifiable risk factors for pancreatic cancer are tobacco smoking and body fatness
- The carcinogenesis of pancreatic cancer remains largely unknown. However, some potentially curable precursor lesions and a set of significantly mutated oncogenes or tumour suppressor genes have been identified
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