Diabetes and Colorectal Cancer
Source: Shutterstock.
Nothing says “it’s complicated” like having diabetes.
The chronic, metabolic disorder occurs when the body is unable to regulate the levels of sugar in the bloodstream. This can result from insufficient insulin production, or the body not responding well even when insulin is produced.
Retina damage (left) — identifiable by the irregular yellow spots — and foot ulcer (right) resulting from diabetes.
Source: Kateryna Kon/Science Photo Library, Ism/Science Photo Library.
Among the complications that can arise from diabetes are blindness, foot problems that may require eventual amputation, and cardiovascular diseases like heart attack and stroke, to name a few. That’s not the end of it, though. Diabetes is associated with an increased risk of colorectal cancer, the third-leading cause of cancer-related death in both men and women.
Diabetes and colorectal cancer
Through multiple studies, the association between increased colorectal cancer risk and diabetes is well-established, though the risk varies with different factors.
In one particular study, almost 2,800 out of about 300,000 diabetic patients were found to develop colorectal cancer. Those diagnosed with type 2 diabetes were observed to have a 1.3-fold increased risk of colorectal cancer, while another study showed that diabetes increases the colorectal cancer risk in adults up to age 65, though there was no association in those older than 65.
A blood glucose test measures the level of glucose (sugar) in the blood.
Source: Shutterstock.
Other studies have also found that the incidence of colorectal cancer is higher among diabetic men compared to women, and that diabetic colorectal cancer patients have a lower 5-year survival rate compared to non-diabetic patients.
These studies focus primarily on patients diagnosed with type 2 diabetes, also referred to as adult-onset diabetes and is characterized by insulin resistance, where cells do not properly respond to the insulin produced. This typically occurs in older adults, and is often combined with a sedentary lifestyle and obesity. Type 1 diabetes, on the other hand, typically manifests in childhood due to the pancreas being unable to produce insulin as a result of an autoimmune response.
The role of insulin and insulin-like growth factor 1 (IGF-1)
Despite the epidemiological data linking diabetes with colorectal cancer, research on the actual pathophysiological mechanisms is still ongoing. Among the hypothesized causes is hyperinsulinemia, in which high levels of insulin and insulin-like growth factor 1 (IGF-1) are thought to promote the proliferation of cancerous cells in the colon.
While insulin and IGF-1 are not mutagenic and are essential hormones in both growth and homeostasis, insulin has been found to also stimulate growth of colon lining and cancer cells in vitro. Additionally, these cells express IGF-1 receptors; colon cancer cells in particular express higher levels of insulin-binding receptors compared to normal epithelial cells.
Collectively, it’s hypothesized that this confers the cells a “survival advantage”, thanks to the anti-apoptotic and pro-proliferative action. Not only does this have implications on the use of insulin as part of diabetes mellitus therapy but also on concurrent colorectal cancer treatment in diabetic patients.
Why it matters
Globally, different nations have an agreed target to halt the rise in diabetes by 2025, and it’s not difficult to see why.
In the US, the prevalence of diabetes in adults above age 18 is on the rise, with about 11.3% of the US population (37.3 million) diagnosed with diabetes, of which 90-95% of diabetes cases are classified as type 2 diabetes.
The incidence of diabetes in 2004 and 2021.
Source: CDC
Even more worryingly, the incidence of prediabetes is also high, with 38% of the US population aged 18, and almost 50% of the population aged 65 and above having prediabetes. In prediabetes, levels of insulin could be even higher than in diabetes.
With a growing population of individuals at risk of colorectal cancer, addressing prediabetes and diabetes not only as a health risk in and of itself but also as a cancer risk factor is key in not just treatment and survival, but also early diagnosis of colorectal cancer.
Colorectal cancer is largely considered an age-related disease, with the risks of developing it increasing from one’s 40s onwards. However, given that age is not a decisive factor for increased cancer risk in diabetic patients, this may present a case for earlier cancer screening for these at-risk individuals, and go a long way in successful treatment and recovery.
