Although cancer and diabetes are separate healthcare issues with different treatment plans, new research shows that they might be more connected than we think. Is it possible that diabetes causes cancer or that cancer could trigger diabetes in certain populations? Keep reading to learn if and how they’re connected.

Discovering The Link Between Cancer and Diabetes

Cancer is characterized by the uncontrollable growth of cells, and diabetes affects how your body produces energy. So how could they be similar in any way? Well, both conditions interrupt the body’s metabolism, which can create a series of risks to the body. In fact, some research, both new and old, suggests that these diseases can develop from one another.

The idea that there is a link between cancer and diabetes goes back to almost 1910. Back then, Dr. G.D. Maynard decided to compare the cancer death rate with other diseases, and diabetes stood out. In his research, he found that both conditions had the same age distributions, an increasing prevalence, and unknown etiologies.

Fast-forward to around 1920, German physiologist Otto Warburg stumbled upon something interesting about cancer cells. He realized that those cells were more inclined to convert glucose to lactate to produce energy even in the presence of oxygen.

Usually, human cells prefer the process of aerobic respiration, where oxygen is used to create energy in the mitochondria. However, the Warburg Effect suggests that cancer cells have defective mitochondria, which is why they rely on the breakdown of glucose for energy production instead.

Given that cancer cells primarily utilize glucose and diabetes is associated with elevated blood glucose levels, it’s not far-fetched to assume a connection exists. Here are some ways that these two diseases seem to overlap.

Does Diabetes Increase One’s Risk of Developing Cancer?

Many studies have shown that diabetes may increase one’s risk of cancer, but interestingly, it doesn’t present equally in both sexes. In 2018, a systemic review and meta-analysis were done to determine if women and men with diabetes have the same risk of developing cancer. They discovered that women with diabetes were 6% more likely to develop cancer than males with the condition. However, they also noted that risk factors differed depending on parts of the body.

For example, men with diabetes were more likely to be diagnosed with liver cancer. Yet women were more likely to develop leukemia (15%), stomach cancer (14%), oral cancer (13%), and kidney cancer (11%) when compared to men.

The increased risk of cancer among people with diabetes is even present when looking at sex-specific cancers. Women with diabetes have an increased risk of developing ovarian cancer, likely due to hyperglycemia. High blood glucose levels are common with diabetes, allowing glucose to feed cancerous cells amply. As a result, they end up growing larger much more quickly than in women without diabetes.

Men with diabetes also have a higher risk of developing prostate cancer, but not because of glucose. Hyperinsulinemia, or high insulin levels, could be the link between type 2 diabetes and prostate tumors. In addition, having pre-existing diabetes is tied to a 32% increase in mortality among prostate cancer patients.

While it is unknown why women with diabetes have a greater risk of developing cancer, there are some theories behind it. Some potential reasonings for this disparity include:

  • Diabetic women tend to be more obese than diabetic men.
  • On average, women are in a pre-diabetic state of impaired glucose tolerance for two years longer than men.
  • Women are often undertreated initially for their diabetic symptoms.

Can Cancer Increase One’s Risk of Diabetes?

It has not only been patients with diabetes who are at a greater risk of developing cancer. In fact, anywhere from 8%-18% of cancer patients have diabetes. Some studies suggest that diabetes may derive from certain cancers or be a side effect of cancer treatment. This is known as secondary diabetes.

A study by the University of Copenhagen’s Department of Nutrition, Exercise, and Sports evaluated over 112 million blood samples from 1.3 million Danes. Of that sample, 50,000 individuals had developed cancer. The study determined that a person affected by lung, pancreatic, breast, brain, urinary tract, or uterine cancers had a higher risk of developing diabetes.

The researchers believed that cancer might secrete substances into various organs that may increase the occurrence of diabetes. However, they indicated that cancer therapies play a significant role too.

Research Shows That Cancer Treatments May Cause Diabetes

While it is expected that some treatments can help ward off diseases, when it comes to diabetes and cancer, the effects of treatment can be negative.

Arthur Riggs, P.h.D., director of the Diabetes & Metabolism Institute at City of Hope, stated, “There are forms of chemotherapy that induce insulin resistance, bringing on symptoms of diabetes.”

Some studies have revealed that chemotherapy agents may result in cellular DNA damage, which can lead to disproportionate cell death in rapidly dividing cells. For instance, a 2015 study evaluated a 34-year-old man with rectal cancer who received the oral chemotherapy agent Tegafur-uracil. One day he presented to the hospital with nausea and abdominal pain and was found to have hyperglycemia and an HbA1c level of 6.8%. He was then diagnosed with type 1 diabetes. Because of this incident, clinicians have been urged to consider diabetes when evaluating chemotherapy patients with gastrointestinal symptoms.

Another chemotherapy agent, interferon alpha, may destroy insulin-producing pancreatic beta cells. Interestingly, with type 1 diabetes, the immune cells attack those same beta cells, and the pancreas stops creating insulin. Therefore, it’s easy to assume this chemotherapy drug could induce diabetes.

Immunotherapy is a revolutionary cancer treatment method involving cell therapy, cancer vaccines, and oncolytic viruses to manipulate the immune system. This manipulation causes the immune system to recognize and attack cancer cells. Unfortunately, even this form of cancer treatment has been shown to drive the development of type 1 diabetes.

Hormonal agents that could be used to block or increase hormones in the cases of prostate or breast cancers can also cause an increase in blood sugar levels. Even steroids for pain and cancer treatment have been shown to increase insulin resistance. Fortunately, it seems administering steroids on small levels can effectively help sugar levels stay within a normal range.

Diabetes Medications and Cancer

It’s possible that some diabetes medications may cause cancer too. In early 2023, Merck & Co. discovered that their medications, Januvia and Janumet, may lead to cancer development. Specifically esophageal, liver, stomach, and kidney cancers. Both medicines have high levels of nitrosamines, which are chemicals often found in toys. It has been found that almost 75% of nitrosamines are carcinogenic in mammals when exposed for long periods of time.

On the flip side, it’s possible that some diabetes medications could lower cancer risk. Metformin is associated with a lower risk of cancer development for diabetics. In addition,  if cancer is contracted, there is a lower mortality rate than people with diabetes who contract cancer and take a different medication.

Take Action To Prevent Both Conditions

For now, medical professionals recommend working to maintain a healthy lifestyle in order to avoid diabetes. Taking active measures to lower one’s risk of diabetes development can also go hand-in-hand with combating someone’s risk of developing cancer. Avoiding diabetes means preventing glucose levels from skyrocketing, which may also decrease the likelihood of glucose fueling cancer cells.

Though these diseases can develop due to other factors, it is evident both feed off each other in a way that has adverse effects on the body. Avoiding one disease can also actively help prevent the other one.

One active prevention factor is physical activity, which has been proven to lower diabetes and cancer risks.

Diabetes and Cancer: The Research Continues

While there has been a link between diabetes and cancer formed decades ago, the research to understand the connections between the diseases continues. Medical advancements and clearer communications in the field allow researchers to focus their studies on both disorders.

Since treatment for one disease can cause a higher risk of development of the other, clinicians should also focus on creating a bridge of communication with one another to share their findings.

What were thought to be two different diseases are very linked. When taking into consideration new treatments for diabetes and cancer, experts must be able to ensure effective symptom treatment while disabling development risks.

Much work is still needed to research and develop effective diabetes and cancer treatments. Hopefully, the near future involves medical professionals finding a solution that effectively fights one disease without increasing the risk of getting the other.