AMSTERDAM—A meta-analysis of 20 individual studies published after 2007 has confirmed a link between diabetes and the risk of developing and dying from breast and colon cancers, according to findings presented here at the European Cancer Congress (Abstract 1402, accessed via http://eccamsterdam2013.ecco-org.eu/Scientific-Programme/Abstract-search.aspx#).
Kirstin De Bruijn, a doctoral student in the surgery department at Erasmus University Medical Center in Rotterdam, the Netherlands, explained that a growing body of data has suggested a link between diabetes and cancer, prompting the analysis, which was conducted from the records of almost two million patients with breast or colon cancer with or without diabetes. The results exclude other causes of death and so give accurate assessments of the contributing influence diabetes had on these two diseases, she said.
The study showed that patients with diabetes had a 23 percent increased risk of developing breast cancer (hazard ratio: 1.23; 95% CI 1.12-1.34) and a 38 percent additional risk of dying from it (HR: 1.38; 95% CI 1.20-1.58). The incidence of colorectal cancer associated with diabetes was found to be 26 percent higher (HR: 1.26; 95%CI 1.14-1.40) with mortality raised by 30 percent (HR: 1.30; 95%CI 1.15-1.47). The studies had no, or only moderate, heterogeneity and there was no evidence of publication bias.
The researchers warned about a looming cancer threat in the future fueled by diabetes stemming from the global pandemic of obesity: “For the future it's worrisome, because the forecasts of obesity are only rising. And because obesity is linked to diabetes, and diabetes is linked to cancer, we think people need to be aware of this association,” they said.
Most of the patients with diabetes had type II disease, meaning that causative factors can usually be addressed to prevent the threat, De Bruijn said.
Asked if diabetes was an independent risk factor for cancer, she said that although most of the individual studies in the meta-analysis were uncorrected for the influence of body mass index, the team did make some different assessments—not fully comparable to the main meta-analysis—using hazard ratios adjusted for BMI, and those did indicate a positive answer. “It was a significant risk, so that indicates that diabetes is an independent risk factor,” she said.
She added that although the study was not able to look at whether anti-diabetic treatment influenced cancer risk, she did suspect that treatment would be beneficial, similar to the evidence from other studies about the positive and negative influences discovered about cancer risk associated with some types of insulin and with metformin.
In her presentation at the conference, De Bruijn said she was eager to get the message out to the public at large: “People should be aware that diabetics—already a more vulnerable population—are at increased risk of getting cancer—so people should be aware. And prevention campaigns should make the ‘normal’ population aware of the risk of diabetes and cancer. Now it's already known among researchers and among doctors, but the average population should know about this risk.”
European Cancer Organization 2012-2013 President Cornelis van de Velde MD, PhD, Professor of Surgery at Leiden University in the Netherlands, said the study was important in the context of the increasing incidence of both diabetes and breast cancer: “This is an important update of meta-analyses as the study excluded other causes of death.”
He said he looked forward to further research findings on the influence that competing risk factors have on mortality—especially in the elderly—and about the potential role of metformin on cancer recurrence and patient survival.
Professor Hans-Joerg Senn MD, Scientific Director of the Tumour and Breast Centre ZeTuP in St Gallen, Switzerland, called the results “disturbing and highly important for the medical community, as well as for the public and politicians.
“It is time for increased—and more effective—information and prevention campaigns, especially in the economically developed world where caloric abundance is prevalent,” he said.
Hear Kirstin De Bruijn discuss more about her findings about the links between diabetes and breast and colorectal cancers in a video interview at the Congress with Peter Goodwin.
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