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Diabetes and cancer are often treated as two separate health concerns. However, growing scientific evidence suggests that the two diseases may be more closely connected than previously understood. A new review published in Diabetes Therapy has highlighted this relationship, reporting that people with diabetes had higher incidence rates of 21 out of 24 common cancers in a nationwide analysis involving nearly five million individuals.
The association was particularly pronounced for liver and pancreatic cancers, while higher rates were also observed for colorectal, breast, endometrial and several other malignancies. Importantly, the relationship works both ways. Cancer itself, as well as certain treatments used to manage the disease, can interfere with blood sugar regulation and increase the risk of developing diabetes.
The findings are particularly relevant for India, which has an estimated 101 million adults living with diabetes and another 136 million with prediabetes. The review also highlights emerging evidence from South India linking type 2 diabetes with oral cancer. Researchers say these findings underline the need to consider metabolic health as an integral part of cancer prevention, treatment and survivorship care.
Diabetes Associated With 21 Of 24 Common Cancers: What The Study Found
The review, titled The Bidirectional Relationship Between Diabetes and Cancer: Mechanistic Insights, Epigenetic Intermediaries, and Therapeutic Approaches, was published in Diabetes Therapy in 2026.
The authors examined epidemiological studies, clinical research and laboratory evidence to understand how diabetes and cancer may influence each other.
One of the findings highlighted was from a nationwide analysis of nearly five million individuals, which reported higher cancer incidence among people with diabetes for 21 of the 24 most common cancers. The relative increase ranged from 11% for non-Hodgkin lymphoma to more than 200% for liver cancer.
The review identified pancreatic, liver, colorectal, breast, endometrial, bladder, kidney, gallbladder, thyroid, stomach and ovarian cancers among those associated with higher incidence in people with type 2 diabetes.
However, the association was not uniform across all cancers. Prostate cancer, for instance, has been associated with a lower incidence among men with type 2 diabetes. Researchers suggest that differences in testosterone and prostate-specific antigen levels, as well as screening patterns, could partly explain this observation.
The authors caution that these findings do not establish that diabetes directly causes every cancer associated with the condition. Shared risk factors and other biological mechanisms may also contribute.
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How Can Diabetes Increase The Risk Of Cancer?
The review identifies several biological mechanisms that may explain the relationship between diabetes and cancer.
1. Insulin resistance and elevated insulin levels
In type 2 diabetes, the body becomes less responsive to insulin, a hormone that helps regulate blood glucose. The pancreas may compensate by producing more insulin, resulting in persistently elevated insulin levels.
High insulin levels can activate insulin-like growth factor 1 (IGF-1) signalling pathways, which influence cell growth, multiplication and survival. Excessive activation of these pathways may encourage tumour development and progression.
2. Persistently high blood sugar
Chronic hyperglycaemia, or elevated blood glucose, can increase oxidative stress and the production of advanced glycation end-products. These processes may damage DNA and contribute to genetic instability, potentially creating conditions favourable to cancer development.
3. Chronic inflammation
Diabetes, particularly when accompanied by obesity, is associated with persistent low-grade inflammation. Inflammatory molecules such as interleukin-6 (IL-6) and tumour necrosis factor-alpha (TNF-alpha) can influence cellular pathways involved in tumour growth and progression.
4. Epigenetic changes
The review also examines epigenetic mechanisms, which influence how genes are switched on or off without changing the underlying DNA sequence. Changes in DNA methylation, histone modifications and non-coding RNA activity may affect genes involved in insulin signalling, inflammation and tumour suppression.
These mechanisms are interconnected and may collectively contribute to the increased cancer risk observed in some people with diabetes.
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Diabetes And Oral Cancer: What Indian Research Reveals
An important aspect of the review is its examination of evidence from South India, where researchers have reported a higher prevalence of diabetes among people with oral cancer. Studies conducted at tertiary diabetes and cancer care centres have also identified an increased frequency of self-reported oral cancer among people with type 2 diabetes.
The review highlights the role of insulin and IGF-1 signalling, including changes in the IGF-1/IGFBP pathway and activation of the WNT pathway, as possible contributors to oral cancer development.
Poor blood sugar control has also been associated with worse clinical outcomes among people living with both diabetes and oral cancer.
Given India's substantial burden of both diabetes and oral cancer, the findings highlight the importance of addressing metabolic health alongside established cancer risk factors such as tobacco use and alcohol consumption.
Cancer Treatments Can Also Trigger Diabetes
The relationship between the two diseases is not one-sided. The review estimates that diabetes affects approximately 8% to 18% of cancer patients worldwide. It also cites a pooled analysis of 13 cohort studies which found that cancer survivors had a 39% higher risk of developing diabetes compared with people without a history of cancer.
Certain cancers and their treatments can disrupt the body's ability to regulate blood glucose.
- Pancreatic cancer: Damage to the pancreas can affect insulin-producing cells. Surgery or radiation involving the organ may also contribute to secondary diabetes.
- Steroids: Glucocorticoids such as dexamethasone, commonly used alongside cancer treatment, can increase insulin resistance and stimulate glucose production in the liver.
- Targeted therapies: Certain mTOR and PI3K/AKT inhibitors can interfere with insulin signalling and glucose regulation.
- Immunotherapy: Immune checkpoint inhibitors, including PD-1 and PD-L1 inhibitors, can trigger autoimmune diabetes resembling type 1 diabetes in some patients.
- Hormone therapy: Androgen deprivation therapy used in prostate cancer has been associated with insulin resistance and a higher risk of diabetes.
These treatment-related effects make blood glucose monitoring particularly important during and after cancer treatment.
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Why Integrated Diabetes And Cancer Care Matters
The researchers call for closer coordination between diabetes and cancer care services. People with diabetes should continue to follow age- and risk-appropriate cancer screening recommendations rather than assume that routine screening alone needs to be intensified because of diabetes.
The review also identifies unexplained weight loss, anaemia, jaundice and persistently elevated inflammatory markers as findings that warrant appropriate medical evaluation, particularly when they occur alongside changes in metabolic health.
Similarly, cancer patients receiving treatments known to affect glucose regulation may benefit from periodic blood sugar assessments, even if they did not previously have diabetes.
Lifestyle measures such as regular physical activity, maintaining a healthy weight and a balanced diet can help improve insulin sensitivity and reduce metabolic risk. Metformin has also been studied for its potential effects on cancer-related pathways, but current evidence does not establish it as a cancer-prevention treatment.
The relationship between diabetes and cancer is complex, involving shared risk factors, metabolic disturbances and, in some cases, the effects of cancer treatment itself. While the association with 21 of 24 common cancers is significant, it should not be interpreted as proof that diabetes directly causes all these malignancies. The findings reinforce the importance of better blood sugar management, appropriate cancer screening and metabolic monitoring during cancer treatment. For India, integrating diabetes management with cancer care could become an important part of improving long-term health outcomes.
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