Diabetes diagnosis linked to cancer development?

Interview conducted by April Cashin-Garbutt, MA (Editor)Oct 6 2016

An interview with Professor Iliana Lega,MD, MSc, FRCPC conducted by April Cashin-Garbutt, MA (Cantab).

Professor Iliana LegaTHOUGHT LEADERS SERIES...insight from the world’s leading experts

How much evidence is there that people with type 2 diabetes are at an increased risk of developing cancer?

There are many studies that support a link between type 2 diabetes and risk of cancer. The relationship is complex and multifactorial.

There are shared risk factors (i.e. obesity, low physical activity, poor diet) that predispose individuals to both conditions, however the metabolic changes seen in early diabetes (i.e. hyperinsulinemia) also act as a growth promoters for cancer cells.

What were the main findings of your recent study and how do they fit with what was previously known?

Our study examined differences in cancer diagnosis between people with and without diabetes at different time points around the time of diabetes diagnosis.

We found two interesting trends. First, people with diabetes have a higher risk of cancer, however the risk is highest in the first 3 months following a diagnosis of diabetes.

Second, we found that people with diabetes are more likely to have had cancer prior to even being diagnosed with diabetes. This supports existing hypotheses that shared risk factors may be contributing to both cancer and diabetes diagnoses.

Why do you think the highest risk appears shortly after a diabetes diagnosis?

We observed an increased risk for cancer immediately following a diagnosis of diabetes which did not persist long term after the diagnosis of diabetes. This may in part be explained by increased health care visits and investigations following a diagnosis of diabetes that also lead to screening tests that reveal a cancer diagnosis.

However, we also found that cancer risk was increased even prior to diabetes suggesting that the cancers diagnosed immediately following a diagnosis of diabetes likely predate the diabetes diagnosis. This may therefore indicate an opportunity for cancer screening in this population.

Is it likely that shared risk factors may be contributing to both diabetes and cancer diagnoses?

Shared risk factors definitely contribute to both conditions. Of the modifiable risk factors, obesity is likely the most important shared factor that has been associated with both cancer and diabetes. However low physical activity, poor diet are also important modifiable risk factors for both conditions.

Could lifestyle changes for diabetes also help to reduce cancer risk?

There is robust evidence from randomized control trials that diabetes can be reversed and prevented with exercise and weight loss interventions.

There is also evidence from observational studies that higher levels of physical activity are associated with a reduction in certain cancers.

What further research is needed to examine the impact of exercise and healthy diet on cancer risk for patients with diabetes?

This is an important question that needs to be answered: do individuals at risk for diabetes have a reduction in cancer risk with exercise and diet interventions.

No studies to date have looked at the impact of a healthy lifestyle on reducing cancer risk in diabetic or pre-diabetic patients.

What do you think the future holds for patients with diabetes and cancer?

There are currently no cancer screening guidelines specifically for patients with diabetes. Our findings suggest that people with diabetes, and especially those at risk for diabetes, may have a higher risk of cancer and therefore they may benefit from enhanced cancer screening and prevention programs.

With more research and evidence in this area, I suspect that there will be specific cancer screening programs developed targeting this population.

Where can readers find more information?

http://onlinelibrary.wiley.com/doi/10.1002/cncr.30095/abstract

About Professor Lega

Dr Iliana Lega MD, MSc, FRCPC is an Associate Professor in the department of Medicine at the University of Toronto, and a clinician scientist at Women’s College Research Institute in Toronto, Canada. She works as a staff endocrinologist at Women’s College Hospital.

Dr. Lega’s research focuses on the complex relationship between diabetes and cancer. Her work has examined the impact of diabetes and diabetes-related treatments on breast cancer outcomes and she is a co-investigator on a study examining disparities in cancer treatments among patients with diabetes. Other research interests include cancer survivorship and endocrine complications following cancer treatments.