Cancer of the colon and rectum affects about 6% of western populations and carries a mortality approaching 50%. Colon cancers are commonly preceded by precancerous polyps that can be removed by a simple endoscopic procedure. Rectal bleeding, which is often not visible, is a common occurrence in early cancer.

Approximately 20% of colorectal cancer causation is due to genes and 80% due to environment – particularly diet. Colorectal cancers of individuals with a strong family history of colorectal cancer often occur at young age e.g.45-55 years and these individuals are likely to benefit substantially from regular colonoscopic screening. The case for screening the “normal risk” population is less straightforward.

Screening of stool samples for non-visible (“occult”) blood reduces mortality from colorectal cancer by about 15% and is cost-effective. Such screening is currently offered for all adults over 60 in England and Wales. The average increase in life expectancy achieved by occult blood screening over age 60 has been estimated at 3.8 days. Screening by direct endoscopic visualisation of the distal colon (flexible sigmoidoscopy) is substantially better but is still likely only to improve life expectancy on average by a few weeks (but with large variations around this) and complete abolition of all deaths from colorectal cancer would only increase average lifespan by about 4 months.

An alternative (or additional) approach is to get a better understanding of the dietary factors that affect risk for colorectal cancer. Professor Rhodes will discuss this in some detail and include the potential for soluble plant fibres found in leafy green vegetables (eg broccoli) and soft fruit (eg bananas) to block potentially harmful interactions between intestinal bacteria and the lining of the colon.

There is also a large body of data suggesting that a high calorie intake from any source and infrequent physical exercise are also powerful risk factors for colorectal cancer. Lifestyle alterations that took these risk factors into account would not only be likely to reduce the risk of colorectal cancer but also substantially to reduce the risk of death from other commoner causes of premature death e.g. heart disease, stroke and diabetes.

The 12th Annual De Pazzi Lecture, held in honour of Sr De Pazzi, retired Matron of Mercy University Hospital, is being hosted by the Alimentary Pharmabiotic Centre and the Department of Medicine at UCC in association with Mercy University Hospital, will take place on Tuesday 14th September at 6pm in Lecture theatre G10, Brookfield Health Sciences Complex, UCC, College Road, Cork. Admission is free and all are welcome.

Picture: Mercy University Hospital, Cork

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