Mortality From Non-Obesity-Related Cancer Higher in T2D Patients

Becky McCall

October 03, 2018

BERLIN - Both men and women with type 2 diabetes are at greater risk of dying from non-obesity-related cancers, as well as being more likely to die from obesity-related cancers than those without type 2 diabetes, finds a UK population-based study investigating associations between type 2 diabetes, body mass index (BMI), and cancer mortality. 

Presenting at the European Association for the Study of Diabetes (EASD) 2018, Miss Nasra Alam, a colorectal surgeon in the North West of England currently undertaking a PhD at the University of Manchester, also looked at the relationship between increasing BMI and cancer mortality. "No consistent relationship was found between increasing weight and risk of cancer death in people with type 2 diabetes," she told Medscape News UK.

But she expressed her surprise at the finding of unexpectedly high mortality from non-obesity-related cancers in patients with type 2 diabetes, which was higher in women than men. "These results suggest that there are mechanisms at play other than obesity causing these non-obesity-related cancer deaths. We need to look at this more."
 

Role of Obesity and Non-Obesity Related Cancers in T2D

Patients with type 2 diabetes are known to have a higher risk of dying from cancer. "I wanted to look specifically at the role of BMI in this," remarked Alam. "Thirteen cancers are documented as being obesity-related cancers, and given the links between weight increase and type 2 diabetes, it makes sense to ask whether these people are also at increased risk of these cancers."

Essentially, Alam wanted to compare people with and without type 2 diabetes in terms of total cancer mortality, and to stratify these findings by obesity-related and non-obesity-related cancers. She also aimed to look at the relationship between increasing BMI and cancer mortality in patients with type 2 diabetes.

Data were sourced on almost 176,886 patients with type 2 diabetes drawn from the Clinical Practice Research Datalink (CPRD), which derives data from 8% of GP practices across the UK.  Patients were matched with 852,946 controls without type 2 diabetes.

Obesity-related cancers included in the analysis were post-menopausal breast, endometrial, ovarian, colorectal, kidney, pancreatic and liver, gallbladder, gastric cardia, oesophageal adenocarcinoma, meningioma, multiple myeloma, and thyroid cancers.

The analysis found that a total of 9606 people with type 2 diabetes died of cancer between 1998-2015. In men, it was found that the total risk of death from any cancer was 22%; with obesity-related cancers, risk of death was 84%; and with non-obesity-related cancers, risk of death was 6%. "The 84% risk of death with obesity-related cancers makes sense and ties in with what we thought. But we didn’t expect to see the increase in non-obesity-related cancer deaths. Essentially, this highlights that if a man or woman has type 2 diabetes they are also more likely to die of non-obesity-related cancer than someone without type 2 diabetes."

In women, mortality figures from any cancer, obesity-related cancers, and non-obesity-related cancers, were 31%, 47%, and 18% respectively. "The non-obesity-related cancer risk was a lot higher in women than in men," Alam pointed out.

With respect to BMI and cancer mortality risk in patients with type 2 diabetes, Alam found that of the 145,769 patients with BMI recorded prior to diagnosis of type 2 diabetes, no relationship was found with either obesity-related or non-obesity-related cancer deaths. "However, when we broke down the results by individual cancer type, there were some patterns. For example, endometrial cancer showed that if your BMI was between 35 and 40 kg/m2, you are four times as likely to die from endometrial cancer if you have type 2 diabetes compared to patients with type 2 diabetes of normal weight."

Commenting on the results, Dr Soffia Gudbjornsdottir, from the University of Gothenburg, Sweden, said that: "It was a large and well-conducted study. The increased risk of obesity-related cancer in those with type 2 diabetes did not come as a surprise but it is a confirmation. But most importantly an increase was seen in non-obesity-related cancers, even at 5% it is important because type 2 diabetes is so prevalent. We have found similar results from a study from Sweden. This is interesting with respect to the potential causal mechanisms here, and we need to study this more."

COI: Miss Alam and Dr Gudbjornsdottir have declared no relevant conflicts of interest.

Presented at EASD 2018. Abstract 1117. Wednesday 2 October, 2018.

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