Cancer incidence remains higher in people with type 2 diabetes, with the gap widening in recent years

A nationwide study being presented at the Annual Meeting of The European Association for the Study of Diabetes (EASD) in Milan, Italy (Sept 28 – Oct 2) has found that people with type 2 diabetes have a higher risk of developing cancer, with cancer incidence rising more than those without diabetes over the past 25 years, largely driven by obesity-related cancers.

Based on data from the entire adult population of Denmark, the study found that overall cancer incidence was 12% higher among men with type 2 diabetes and 22% higher among women with type 2 diabetes compared with those without diabetes in the most recent period (2010–2022)— the corresponding differences in 1996–2009 were 9% and 15%.

Dr Tinne Lauberg from Steno Diabetes Center Arhus, Aarhus University Hospital in Denmark, who led the research, commented: “Our findings underline the growing cancer burden among people with type 2 diabetes and highlight the need to prioritise cancer prevention and early detection as part of long-term diabetes care.

“This is especially important for common obesity-related cancers, such as colorectal and postmenopausal breast cancer, for which screening programmes already exist in many countries. We must ensure that people with type 2 diabetes benefit fully from these established programmes by encouraging greater participation.”

Cancer is a major health condition associated with type 2 diabetes with prolonged exposure to high blood sugar and insulin levels, as well as insulin resistance and ongoing inflammation, potentially contributing to cancer development.

Over the past decade, cancer has become the leading cause of death among people with type 2 diabetes in Denmark and other high-income countries [1]. This makes it important to understand how the incidence of different types of cancer has changed over time. However, population-level data on long-term cancer incidence trends in individuals with and without type 2 diabetes are scarce.

For the study, researchers used data from nationwide health registries to compare the occurrence of new obesity-related and non-obesity-related cancers among adults (aged 18 and over) with and without type 2 diabetes living in Denmark between 1996 and 2022.

Participants were considered to have no diabetes until they were diagnosed with type 2, after which they were classified as having type 2 diabetes. Follow-up began when participants turned 18, immigrated to Denmark or on 1 January 1996 (whichever occurred later), and continued until they were diagnosed with cancer, emigrated, died, or reached 31 December 2022.

Higher incidence particularly evident for obesity-related cancers

During 27 years of follow-up, 75,540 first cancers were identified among individuals with T2D, and 635,323 among individuals without diabetes.

The higher cancer incidence among people with T2D is particularly evident for obesity-related cancers, which were 45% higher in men and 30% higher in women compared to those without diabetes in 2010-2022—the corresponding differences in 1996–2009 were 34% and 23%, respectively.

However, patterns differ substantially by sex and cancer type.

Among the most common obesity-related cancers, postmenopausal breast cancer—the most common cancer among women—had an 8% higher incidence in women with T2D in 2010–2022. Similarly, colorectal cancer, the third most common cancer in both sexes, had a 17% higher incidence in men and a 14% higher incidence in women with type 2 diabetes.

Patterns also differed for common cancers not classified as obesity-related. For example, prostate cancer, the most common cancer among men, had a 19% lower incidence among men with type 2 diabetes compared with those without diabetes in 2010–2022.

In contrast, lung cancer, the second most common cancer in both sexes, was 23% higher in men and 25% higher in women with type 2 diabetes during this period. The difference was particularly notable in women, with incidence 12% lower among those with T2D than those without diabetes in 1996–2009, compared with 25% higher in 2010–2022.

According to Dr Laurberg, “These findings support greater recognition of cancer as a major long-term complication of type 2 diabetes. Cardiovascular and kidney disease prevention remains a key priority in diabetes care. However, as outcomes for these complications improve, cancer may require greater attention as part of the long-term care of people with type 2 diabetes. Our results underline the importance of considering cancer prevention and early detection alongside other established aspects of diabetes care, particularly for common cancers such as colorectal, lung, and breast cancer.”

The researchers emphasise that the study was designed to describe differences in cancer incidence between people with and without type 2 diabetes, rather than to determine whether type 2 diabetes itself causes these differences. Assessing factors that may contribute to the observed differences and changes over time, such as body weight, smoking, alcohol consumption and physical activity, was beyond the scope of the study. They also note that classifying a cancer as obesity-related reflects an established association with obesity at the population level and does not mean that obesity itself explains the differences in cancer incidence observed between people with and without type 2 diabetes.