Diabetes and cancer — obvers and reverse

Diabetes mellitus and cancer are common diseases that affect 425 million and 33 million people worldwide, respectively. Possible biological links include hyperinsulinemia, hyperglycemia and chronic inflammation caused by obesity, as well as insulin-like growth factor-1, excessive cytokine production. The risks of cancer associated with diabetes mellitus type 2 are more than 2 times higher for liver, pancreatic and endometrial cancers, 1,2 and 1,5 times higher for colon, breast and bladder cancers. The prevalence of pre-existing diabetes in cancer patients with cancer of any localization was estimated at 20,7% and appears to be high in patients with liver and pancreatic cancer, regardless of gender. Different types of diabetes mellitus are associated with different localization of cancer: diabetes mellitus type 2 is associated with an increased risk of breast, colon, and pancreatic cancer, while diabetes mellitus type 1 is closely correlated with cancer of the stomach, pancreas, endometrium, and cervix. Obesity, coupled with diabetes, is also associated with an increased risk of endometrial malignancies, colorectal cancer and postmenopausal breast cancer. The increased risk of pancreatic cancer in patients with newly diagnosed diabetes compared to long-term diabetes indicates a complex and bidirectional relationship. Long-term diabetes mellitus is a predisposing factor for pancreatic cancer, increasing the risk of malignancy by 1,5-2 times, and first-time diabetes may be an early manifestation of a tumor. Antidiabetic drugs also have an impact on cancer risk, and drugs used to treat cancer can either cause diabetes themselves or worsen existing ones. There is a relationship between cancer and both type 1 and type 2 diabetes. Metformin may reduce the risk of cancer. Clinical studies performed on insulin glargine give contradictory results, and it is impossible to confirm or exclude the carcinogenic risk of long-acting insulin analogues. When managing patients with diabetes mellitus, especially during its primary diagnosis, it is advisable to undergo cancer screenings recommended according to age and gender.