The Link Between Diabetes and Cancer: Converging Mechanistic and Epidemiologic Evidence

Accumulating evidence indicates that diabetes is associated with increased risk of several cancers. The strongest evidence has been reported for cancers of the breast, colorectum, endometrium, liver, pancreas, and gallbladder. However, distinguishing causal relationships from associations driven by shared risk factors such as obesity, aging, and lifestyle behaviors remains challenging. Several biological mechanisms have been proposed to explain these associations. Key pathways include the effects of insulin resistance and compensatory hyperinsulinemia on mitogenic signaling pathways, including PI3K/AKT/mTOR and MAPK, as well as the influence of adiposity, chronic inflammation, and altered metabolic substrates on tumor initiation and progression. Hyperglycemia may also contribute by promoting tumor metabolism and cellular proliferation, although its independent contribution remains debated. These mechanisms likely interact to create a protumorigenic metabolic environment in individuals with diabetes. Obesity, which frequently co-occurs with diabetes, further amplifies these risks through altered adipokine secretion and increased estrogen production, highlighting the interrelated contributions of metabolic and hormonal factors. The relationship between diabetes and cancer has important clinical implications. Diabetes has been associated with worse cancer prognosis and higher cancer-related mortality, highlighting the importance of integrated management strategies. The impact of antihyperglycemic therapy on cancer risk and progression has been extensively studied, and ongoing research continues to evaluate potential protective or tumor-modifying effects. In this article, we summarize the epidemiologic and pathophysiologic evidence describing the relationship between diabetes and cancer and discuss strategies for risk mitigation, screening, and management.