Diabetics could be up to three times more likely to get bowel cancer

People with diabetes could be up to three times more likely to get bowel cancer – according to a report from Cancer Research UK and the Medical Research Council published*(1) today.

Scientists tested a marker of the sugar levels in blood samples*(2) taken from almost 10,000 men and women aged between 45-79 and then checked their medical condition six years later.

They found that people with diabetes – and those with abnormal glucose metabolism which could lead to diabetes – were more likely to develop colon cancer.

Professor Kay-Tee Khaw, who led the study which was jointly funded by Cancer Research UK and the Medical Research Council, says: "The study shows that high sugar levels, even when they are below those of diagnosed diabetes, could be linked to increased risk of bowel cancer.

"More research is needed but if the results of our study are confirmed they would be important in developing prevention strategies."

Earlier research suggested that those lifestyle factors known to reduce the risk of diabetes – such as increased exercise, maintaining a healthy weight and a diet high in fibre – also help to prevent bowel cancer.

The report, which comes from the Norfolk arm of the European Prospective Investigation into Cancer*(3) (EPIC – Norfolk), was undertaken to investigate the existing evidence that suggests abnormal glucose metabolism may be associated with increased risk of colorectal cancer.

Participants in the study first filled out health and lifestyle questionnaires and were then invited for a medical examination which included blood samples being taken.

Six years later when 9,600 participants were followed up 67 were found to have developed bowel cancer. Studies showed that the diabetics were three times more likely to develop bowel cancer than the rest of the participants. And the trend was stronger in men than women.

Previous research has offered possible reasons for an association between glucose metabolism and cancer risk. Prof Khaw says that both diabetes and bowel cancer may share common predisposing factors. It is already accepted that a high fibre diet and regular exercise can help protect against both diseases.

Alternatively, hormonal changes associated with diabetes could promote tumour risk.

"Instead of looking at insulin we measured glycated haemoglobin – a marker of blood glucose levels over the past few months – which is likely to be a good indicator of metabolic processes that influence insulin levels," she says.

"Understanding these metabolic changes, and the lifestyle factors responsible, may help us to prevent and treat cancer."

Prof Robert Souhami, Director of Clinical and External Affairs, says: "Colorectal cancer is one of most common cancers and is the second most common cause of cancer death. This puts it at the top of the research agenda and any information that helps formulate prevention strategies is welcome."

*(1) Cancer Epidemiology and Biomarkers: Vol 13; No. 6
*(2) glycated haemoglobin
*(3)The EPIC study began in 1992 and is looking prospectively at the diets of 400,000 men and women aged 45 – 74 years in nine European countries. Extensive social, medical and lifestyle information is being collected as well as biological samples.