A research team at the German Cancer Research Center (DKFZ ) has gained new insights into the link between diabetes and an increased risk of colorectal cancer. The study shows that tumors with low immune cell density, so-called immunocold tumors, are particularly susceptible to the harmful effects of diabetes. These findings could help to better target prevention and treatment strategies for colorectal cancer patients with diabetes.

In a large-scale study with 4,724 participants, including 2,321 colorectal cancer patients, the scientists investigated the tumor microenvironment, in particular the density of immune cells such as T lymphocytes, which fight cancer cells. Tumors with a high immune cell density can control cancer better, while immunocompromised tumors often grow more aggressively and respond less well to therapies. The researchers found that diabetes promotes the development of immune-cold tumors. Diabetes patients with such tumors had a significantly worse prognosis over a follow-up period of 9.5 years, with a higher risk of cancer recurrence and a lower chance of survival. Patients with immune-strong tumors, on the other hand, did not show an increased risk.

The scientists suspect that chronically elevated blood sugar and insulin levels promote tumor growth and weaken the energy of immune cells in the tumor microenvironment, which impairs immune control. These findings could improve future assessment of tumour immune status and help physicians develop individualized screening and treatment strategies. People with diabetes could benefit from earlier colorectal cancer screening. In addition, lifestyle changes and better blood sugar control could have a positive influence on immunodeficiency in colorectal cancer, which further studies should clarify.

Original Paper:

Wankhede D, Halama N, Kloor M, Brenner H, Hoffmeister M: Diabetes and Colorectal Cancer Risk and Survival According to Tumor Immunity Status. J Clin Oncol 2025, DOI: 10.1200/JCO-25-00148

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