Endoscopic Characteristics of Colonic Tumours

The purpose is to investigate whether polyps that look different at colonoscopy, have formed via different mutations and have different risks of turning into cancer.

Laterally spreading tumours (LSTs), are polyps that have a lateral extension along the colon wall with minimal vertical growth. It has become evident over the last few years that rather than being a single entity requiring an accumulation of mutations, colon cancer is in fact a heterogenous disease forming via multiple distinct genetic pathways. Additionally, with improved endoscopic characterization, it has been noted from experience at Westmead hospital that two macroscopically distinct types of LSTs, "granular" and "non granular", have different natural histories and risks of invasive cancer. It is therefore hypothesised that different polyp types have different genetic abnormalities, and potentially form via distinct genetic pathways, although this theory has not been widely examined. This knowledge would be important in furthering our understanding of the development of cancer. There is accumulating evidence that genetic abnormalities may be a better predictor of cancer behaviour than histological grade. Additionally, guidelines for colonoscopy surveillance are currently a one size fits all approach that do not reflect the genetic heterogeneity of the disease and the knowledge that only 5% of polyps progress to cancer. Genetic studies may assess future cancer risk to a person in polyps once removed and plan surveillance colonoscopy frequency. This is an area with interest currently due to the national bowel cancer screening programme, with obvious cost implications for decision makers.