A small proportion of gastrointestinal cancers occur in well-described Mendelian inheritance patterns, with many of these being caused by clearly identified genetic mutations. The most studied syndromes causing colon cancer are familial adenomatous polyposis (FAP) and Lynch syndrome, whilst in the stomach, mutations of E-cadherin are responsible for hereditary diffuse gastric cancer syndrome. Collectively, these cases make up less than 10% of gastrointestinal cancers.
Identification of specific genetic mutations has led to an appreciation of the complex mechanisms of cancer pathogenesis, including phenotypic heterogeneity in penetrance, age of onset, organs affected and other associated benign features such as retinal and connective tissue involvement.
Surveillance for such cases aims to detect precursor abnormalities that dictate further management such as surgery, to prevent development of frank cancer. Thus, surveillance decisions include the organs to be examined (e.g., colon, stomach, small intestine, uterus, urinary tract), the age to begin surveillance, surveillance intervals (e.g., Lynch syndrome is biologically characterised by rapid progression through premalignant phases and requires intensive, frequent surveillance) and where necessary, the timing of surgery. Even within a specific syndrome, there is phenotypic heterogeneity between different families and different individuals which require further refinement in surveillance decisions.
While there are surveillance guidelines for numerous inherited cancer syndromes, a further element of tailoring involves informed discussions of risk and choices for each individual. These discussions are best undertaken with multidisciplinary expertise including organ specialists, surgeons and clinical geneticists.