Screening for cancer in high risk families

Genetic causes of cancer predisposition in children and adolescents

The acquisition of de novo somatic mutations accounts for approximately 90% of all new cancer diagnoses, while the remaining 10% is due to inherited genetic traits. In this latter category, individuals harbouring germline mutations show a higher likelihood of developing potentially life-threatening cancers, often at a very young age. The study of cancer genetics has profoundly helped our understanding of cancer biology, leading to better characterised malignancies, tailored targeted therapies and the identification of individuals at high risk of cancer diagnosis. This review will discuss examples of cancer syndromes in children, adolescents and young adults, the main underlying gene mutations, and the use of genetic testing to identify gene mutation carriers. Finally, we will describe how gene mutation detection is employed for the life-long management of patients with high susceptibility to cancer, including genetic counselling, increased surveillance, early intervention and use of targeted therapies.

Health economics and genetic service development: a familial cancer genetic example

Advances in genetics are allowing a greater number of clinical genetics services to be offered to individuals with family histories of particular diseases. It is important that such services are not allowed to proliferate before they have been properly evaluated in terms of both their clinical and cost-effectiveness. A randomised controlled study of a new clinical genetics service in Wales for women with a family history of breast cancer has been undertaken. The health service costs from initial consultation and counselling through to mutation testing within families were assessed, along with patient travel costs. The extra cost of specialist genetics assessment (intervention) was pound 16.36 higher per woman than assessment by a breast surgeon at a District General Hospital (control). A further cost of pound 46.42 per initially presenting woman was also generated as a result of further counselling within the families of 48, and testing within the families of 36 of the 412 original presenting women. An explanation is given here of the costing methodology as an illustration of what is involved in such an exercise.

Association between breast and colorectal cancers

BACKGROUND

The risk of breast and colorectal cancers in immigrants from non-industrialised countries is sharply increased when they adopt a Western lifestyle. In addition, epidemiological studies on Western populations show an association between the two tumours, both in the same individual and also in close relatives. Most studies agree that high energy intake, obesity and inadequate physical exercise are associated with an increased risk of both tumours.

METHODS

Risk markers for each cancer are examined in order to identify causative nutritional factors or metabolic-endocrine dysfunction. The role of steroid hormones and other possible carcinogenic mechanisms is discussed, concentrating on evidence of a role for insulin and insulin-like growth factors (IGFs) in the promotion of carcinogenesis in both organs.

RESULTS

Individuals with a genetic susceptibility to insulin resistance show triggering of hyperinsulinaemia following excessive weight gain or long-term diet high in saturated fat. Case-control studies show an association between hyperinsulinaemia and evidence of breast or colorectal carcinoma. Multiple laboratory studies show that increased activity of IGFs can stimulate the growth of human breast and colorectal cancer cells.

CONCLUSION

It is postulated that either insulin resistance and its concomitants promote the development of breast and colorectal cancers, or that they share common risk factors. Sex steroid metabolism and organ specificity may explain age and sex differences between the tumours in relation to the role of obesity. Recent research suggests that a diet high in n-3 polyunsaturated fatty acids may reduce the risk of developing insulin resistance. This observation may be applied to test the hypothesis that an effect on hyperinsulinaemia may modify the risk of developing breast or colorectal cancer.