Oral Diabetes Medication Adherence Linked to Survival in Patients With Colorectal Cancer

A recent study reports that high adherence to oral diabetes medication was associated with improved survival for patients with colorectal cancer. 

The diabetes epidemic in the United States has left more than 34 million people with this disease, with an additional 88 million adults at risk of developing diabetes due to prediabetes, which often has no symptoms. 

Diabetes increases the risk of developing a host of other health problems, including kidney disease, high blood pressure, and nerve damage. Diabetes has also been associated with an increased risk of several types of cancer, including colorectal cancer.

A study recently published in Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association for Cancer Research (AACR), evaluated whether adhering to oral antidiabetic medications was associated with survival among patients with colorectal cancer and diabetes.

Sunho Choe, MD

While previous studies have found that taking the antidiabetic medication metformin is associated with improved survival in patients with both diabetes and colorectal cancer, many diabetics take additional medications along with metformin to control their disease. Whether the combination of multiple antidiabetic medications affects the prognosis of colorectal cancer remains underexplored, noted lead study author Sunho Choe, MD, a resident physician in the Department of Preventive Medicine at Seoul National University College of Medicine in Korea.

Using the National Health Information Database in Korea, the authors included patients who had diabetes and were diagnosed with colorectal cancer between 2002 and 2016, resulting in a total study population of 33,841 participants. 

The researchers compared survival outcomes among colorectal cancer patients who had different levels of adherence to their prescribed oral antidiabetic medications. To do this, they used prescription data to estimate the patients’ proportion of days covered (PDC), which is defined as the number of days with medication on hand divided by the number of days in a specified time interval. If patients had a PDC of at least 80 percent, they were classified as having high adherence. If patients had a PDC less than 80 percent, they were classified as having low adherence.

The researchers found that over 80 percent of patients were taking more than one oral antidiabetic medication, and less than 23 percent of patients had high adherence to these medications. Compared with patients with high adherence, those with low adherence to their oral antidiabetic medication had a nearly 20 percent increase in their risk of death.

“Based on our data, less than 25 percent of patients were taking their diabetes medications as prescribed, suggesting that over 75 percent of diabetic patients with colorectal cancer could benefit by adhering to these prescriptions,” said senior study author Aesun Shin, MD, PhD, a professor in the Department of Preventive Medicine at Seoul National University College of Medicine.

“Overall, our findings suggest that maintaining a high adherence to oral antidiabetic medications could improve the survival of patients with colorectal cancer,” Dr. Choe said.