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Cancer risk increased before, after diabetes diagnosis
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Individuals with type 2 diabetes appeared to have an increased risk for cancer 3 months following and 10 years preceding their diabetes diagnosis, according to the results of a retrospective population-based study.
“Our findings are important because they underscore the need for further research that examines the impact of exercise and healthy diet on cancer risk specifically in patients with or at risk for diabetes,” Iliana Lega, MD, MSc, associate professor in the department of medicine at Women’s College Research Institute of University of Toronto in Toronto, Ontario, said in a press release. “This supports existing hypotheses that shared risk factors may be contributing to both cancer and diabetes diagnoses.”
Previous research has demonstrated a relationship between type 2 diabetes and liver, pancreatic and endometrial cancers, with a modest association observed for breast, colorectal and bladder cancers.
Lega and colleagues examined the temporal relationship between type 2 diabetes and cancer. They evaluated three time periods: 10 years preceding diabetes diagnosis, 3 months immediately following diabetes diagnosis, and 3 months to 10 years following diabetes diagnosis.
Researchers used the Ontario Diabetes Database to evaluate data from 516,219 adults (46.3% women; mean age, 58 years) who received a diagnosis of diabetes between 1997 and 2007. These participants were compared 1:1 to an age and sex-matched control cohort of participants without diabetes; control participants who developed diabetes during follow-up were censored.
Median follow-up was 5.38 years. Researchers used The Ontario Cancer Registry to identify 36,140 cancers diagnosed among participants in the diabetes cohort and 33,156 cancers in the control cohort.
Within the 10-year period preceding diabetes diagnosis, cancer occurred at a great rate among individuals who would develop diabetes (4.88% vs. 4%; OR = 1.23; 95% CI, 1.19-1.27).
Results of a cancer-specific analysis showed the most common cancers among patients who would develop diabetes included pancreatic (OR = 3.34; 95% CI, 1.94-5.76), liver (OR = 3.12; 95% CI, 1.52-6.39) and endometrial (OR = 1.41; 95% CI, 1.22-1.63) cancers. Those who would develop diabetes also appeared more likely to be diagnosed with the following cancers:
- thyroid (OR = 1.29; 95 % CI, 1.07-1.55);
- colorectal (OR = 1.26; 95% CI, 1.15-1.38);
- lung (OR = 1.26; 95% CI, 1.07-1.49);
- bladder (OR = 1.25; 95% CI, 1.07-1.45);
- breast (OR = 1.24; 95% CI, 1.16-1.34); and
- prostate (OR = 1.13; 95% CI, 1.06-1.2).
In the 3-month period following diabetes diagnosis, the rate of cancers per 1,000 patient-years was greater among those with diabetes than controls (19.3 vs. 10.6; HR = 1.62; 95% CI, 1.52-1.74). The risk appeared highest for pancreatic (HR = 8.13; 95% CI, 5.42-12.2), endometrial (HR = 3.86; 95% CI, 2.46-6.06), thyroid (HR = 2.52; 95% CI, 1.44-4.39) and liver (HR = 2.1; 95% CI, 1.12-3.93) cancers. Increased risks within 3 months following diabetes diagnoses also occurred for cancers of the:
- colon/rectum (HR = 1.29; 95% CI, 1.06-1.56);
- lung (HR = 1.29; 95% CI, 1.08-1.54);
- prostate (HR = 1.44; 95% CI, 1.23-1.68); and
- bladder (HR = 1.85; 95% CI, 1.28-2.67).
Researchers observed no difference in overall cancer risk in the period 3 months to 10 years following diabetes diagnosis (rate per 1,000 person-years, 12.1 vs. 11.1; HR = 0.97; 95% CI, 0.95-0.98). However, those with diabetes appeared to be at increased risk during this period for pancreatic (HR = 1.74; 95% CI, 1.56-1.91), liver (HR = 1.63; 95% CI, 1.42-1.86), endometrial (HR = 1.58; 95% CI, 1.44-1.74) and thyroid (HR = 1.22; 95% CI, 1.08-1.37) cancers.
Researchers acknowledge that a lack of clinical data on hemoglobin A1c, risk factors, comorbidities and medications may have limited findings.
“The findings of the current study have significant potential public health implications given the growing prevalence of diabetes in many countries,” Lega and colleagues wrote. “[Diabetes incidence] projections have implications not only for the future burden of diabetes, but also may mean higher rates of cancer.” – by Nick Andrews
Disclosure: Lega reports a fellowship from the Canadian Breast Cancer Research Foundation. Please see the full study for a list of all other researchers' relevant financial disclosures.
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