A younger man without a shirt with his hands on his hipsShare on Pinterest
Experts say the risk of colorectal cancer is higher in people with type 2 diabetes. Moy Ortega/Stocksy
  • Researchers are reporting that type 2 diabetes is associated with elevated risk of colorectal cancer.
  • They say a study that included predominantly low-income and African-American individuals showed the increased risk to be 47%.
  • Experts say obesity and a lack of access to healthcare and preventive services may be factors.

A new study of predominantly low-income and African-American individuals reports that people who have type 2 diabetes face a 47% increased risk of developing colorectal cancer.

Researchers said the association between diabetes and colorectal cancer was even more pronounced among people who lacked recent colonoscopy screenings and those who had a more recent diabetes diagnoses.

“These findings suggest that given the emerging association between diabetes and elevated risk for colorectal cancer, screening via colonoscopy for individuals with diabetes may help to mitigate risk,” the researchers from the University of Wisconsin wrote.

“Type 2 diabetes is the most common form of diabetes and we know that those who have this form are at a higher risk of developing certain types of cancer including colon, bladder, breast, liver and pancreatic cancer,” said Dr. Sudarsan Kollimuttathuillam, a medical oncologist at City of Hope Huntington Beach and City of Hope Irvine Sand Canyon in Southern California who was not involved in the study.

“While this is a growing area of research, the data is quite clear that the association between diabetes and colon cancer is not coincidental and that the two are closely related from biology to risk factors,” he told Medical News Today.

The study, published in the journal JAMA Network Open, included a cohort of more than 54,000 adults, 66 percent of whom were African American and 53 percent of whom had incomes of less than $15,000 per year.

Researchers led by Thomas Lawler, a lead study author as well as a graduate student and research assistant at the University of Wisconsin-Madison, noted that while past studies have demonstrated an association between type 2 diabetes and elevated colorectal cancer risk, the new study focuses on populations where both conditions are more prevalent but are less commonly studied.

Dr. Quyen Ngo-Metzger, a professor of health systems science at the Kaiser Permanente Bernard J. Tyson School of Medicine who was not involved in the study, told Medical News Today that race and income can lead to decreased access to adequate healthcare and preventive services.

“Having received a diagnosis of diabetes may have increased the opportunity for screening for colorectal cancer and increased the likelihood of finding cancer,” Ngo-Metzger said. “When research studies use ‘race,’ it is important to remember that racial classifications are social construct and have no biological basis. Increasing access to preventive care for African Americans is the most important take-away from this study.”

Kollimuttathuillam noted that obesity is among the main risk factors for both diabetes and cancer. Past studies have shown that younger adults who have obesity or overweight have a higher risk of colorectal cancer.

“Excess fat and inflammation are triggers for both diseases and fat deposits can lead to the start of tumor growth while forming insulin resistance, leading to both cancer and type 2 diabetes,” he said.

The first thing that people with type 2 diabetes can do to lower their risk of colorectal cancer is to get their diabetes under control, said Kollimuttathuillam.

“Some risk factors for colorectal cancer are things you’re born with or other things, like age, that you cannot control,” he said. “Yet, many lifestyle choices can also raise or lower your risk of developing the disease. Factors such as diet, weight, and exercise, for instance, are strongly linked to colorectal cancer.”

“More than most other cancers, colorectal cancer is affected by things you can control, such as what you eat and how much you exercise,” Kollimuttathuillam added. “A healthy lifestyle doesn’t just lower the risk of certain cancers, it has a beneficial impact on the risk of type 2 diabetes, heart disease, and more.”

Diabetes can also affect survivability among people with this form of cancer. In a study published in an October 2023 issue of the journal Cancer, researchers reported that people with diabetes — and especially those with significant complications of the disease — were at higher risk of dying from colorectal cancer than people who did not have diabetes.

In that study, Dr. Kuo‐Liong Chien, a researcher with the National University Taiwan, and his colleagues reported that while people with uncomplicated diabetes had a minimal or only slightly elevated risk of all‐cause or cancer‐specific death during the study period, those with complicated diabetes had an 85% higher risk of death from any cause and a 41% higher risk of death from colorectal cancer.

People with diabetes also were at a higher risk of having their colorectal cancer recur after surgery to remove tumors.

“While a higher diabetes prevalence was noted in patients with colorectal cancer, the study suggests that coordinated medical care involving multiple specialists can help prevent diabetes complications, potentially improving long-term colorectal cancer oncological outcomes, particularly in women and patients with early-stage cancer,” said Chien in a press statement.