The study found that 5.6% of all incident cancers from 5 years ago were attributable to the combined effects of diabetes and high BMI.
A comparative risk assessment has found an association between diabetes, body mass index (BMI), and an increased risk in several forms of cancer.
The study, which estimated population attributable factors for a dozen cancers for residents of 175 countries in 2012, found that 792,600 (5.6%) of all incident cancers that year were attributable to the combined effects of diabetes and high BMI. Among the cancer cases most likely to correlate with the conditions were endometrial cancer (121,700; 38.4%) and liver cancer (766,000; 24.5%).
High BMI, as defined by observed patient’s BMI equating to 25kg/m2 or more, was individually responsible for 544,300 cases of cancer — nearly twice as many as diabetes (280,100). Researchers noted that 77,000 (26.1%) diabetes-related cancers and 174,040 (31.9%) high BMI-related cancers were attributable to the increased prevalence of these conditions in the years between 1980 and 2002.
Noting various studies that have drawn estimated associations between the 2 conditions and cancers, researchers wrote that this study is the first documented estimate of global cancer burden attributable to diabetes alone, or diabetes and high BMI combined.
“Diabetes is increasingly recognized as a risk factor for colorectal, pancreatic, liver, gallbladder, breast, and endometrial cancer, but the global cancer burden attributable to diabetes has not been quantified,” researchers wrote. “Furthermore, since high BMI is an important risk factor for diabetes, priority setting for public health and clinical interventions requires information on the cancer burden attributable to both high BMI and diabetes.”
Using GLOBOCAN cancer incidence data to estimate cancer incidences attributable to the conditions, researchers analyzed rates for each individual country observed, and grouped by region for reporting.
Due to lag between the conditions and cancer being about a decade, researchers calculated the 2012 cancer incidences with attribute to 2002 diabetes and high BMI diagnoses. They were also forced to estimate cancer incidence through data, due high BMI and diabetes having increased “substantially over the past 4 decades in most countries.”
The researchers also found a stronger correlation rate in women with cancer, with diabetes and high BMI attributing to nearly twice as many cases in women (496,700) than in men (295,900).
Biological mechanisms such as hyperinsulinemia, hypergylcemia, chronic inflammation, and the dysregulation of sex hormone activity may be the conditions’ underlying link, researchers wrote.
“Insulin itself could be oncogenic, and results from several analyses showed that people with hyperinsulinemia were at increased risk of breast and colorectal cancer irrespective of their BMI,” researchers wrote.
Unfortunately, the study’s results were more confirmation of well-known information than they were revelatory to the mechanisms of the diseases, Kevin Pantalone, DO, told MD Magazine.
“This confirms what we already suspected,” Pantalone, of the Twinsburg Family Health and Care Center, said. “It really has not been clear what the underlying mechanism of how obesity and diabetes cause cancer risk.”
Pantalone noted that insulin resistance, a commonality in patients with diabetes and obesity, could be an increased risk for cancers — as well as inflammation caused by increased fat tissue.
“The exact mechanism is not clear, but there’s a definite association,” Pantalone said.
Unfortunately, due to the various conditions that also increase cancer risks, the association would have to be proven through a perspective uncontrolled trial of patients with obesity or diabetes. Pantalone said this would call for “huge data sets from an epidemiological look.”
The study, "Worldwide burden of cancer attributable to diabetes and high body-mass index: a comparative risk assessment," was published online in The Lancet last month.