The onset of diabetes after the age of 50 could be an early sign of pancreatic cancer, a new study suggests.
Pancreatic cancer is one of the deadliest cancers, with an overall five-year survival rate of about 8%.
Symptoms of pancreatic cancer include abdominal pain, weight loss and fatigue, according to the Mayo Clinic. Major risk factors include smoking, obesity, old age and family history. Smoking is estimated to cause approximately 30% of pancreatic cancer cases, according to the American Cancer Society.
The study, published Monday in the Journal of the National Cancer Institute, followed nearly 50,000 African-American and Hispanic men and women above the age of 50 for about 20 years. None of the participants had diabetes or pancreatic cancer at the beginning of the study.
Of the nearly 50,000 participants, the researchers identified about 16,000 who developed diabetes and about 400 who developed pancreatic cancer during the 20-year study period.
Those individuals who developed diabetes were more than twice as likely to develop pancreatic cancer compared with those who did not develop diabetes, according to Wendy Setiawan, associate professor of preventive medicine at the Keck School of Medicine of the University of Southern California and a lead author of the study.
"We need to have a better way to identify patients with early pancreatic cancer," Setiawan said. "So we wanted to understand what are the characteristics of people in our study and other populations that help narrow down who are the high-risk populations."
Over 50% of the diabetic individuals with pancreatic cancer were diagnosed with diabetes within three years of being diagnosed with pancreatic cancer, according to Setiawan.
"If you really look at the type of Type 2 diabetes that pancreatic cancer patients have, the majority of those diabetes are diagnosed very, very close to the time of the cancer diagnosis," Setiawan said. "So people with recent-onset diabetes -- which we defined as within 36 months from pancreatic cancer diagnosis -- are at much higher risk for pancreatic cancer."
This suggests that the development of diabetes, especially later in life, could be an early sign of pancreatic cancer for some people, said Dr. Zev Wainberg, associate professor in hematology/oncology and gastrointestinal oncology at UCLA's Jonsson Comprehensive Cancer Center, who was not involved in the new study.
"It suggests that patients with diabetes -- new-onset diabetes in particular -- and their clinicians should monitor and identify their risks for pancreatic cancer," Wainberg said.
But the chances of having pancreatic cancer are still slim, even for those who do develop diabetes after 50, said Dr. Robert Rushakoff, professor of medicine at the University of California, San Francisco and medical director of the UCSF Diabetes Center, who was not involved in the recent study.
"Patients develop Type 2 diabetes at a later age. It is a common disease. Pancreatic cancer is relatively rare. There is no indication for general screening for pancreatic cancer in patients with diabetes," Rushakoff wrote in an email. "These findings don't do anything to change how diabetes patients are diagnosed or treated."
The pancreas is an abdominal organ that has many functions, including the regulation of blood sugar. It regulates sugar by producing insulin, which reduces blood sugar levels, and glucagon, which increases blood sugar levels. Diabetes occurs when either the pancreas doesn't produce enough insulin or the body's tissues become resistant to insulin, resulting in increased blood sugar, according to the Mayo Clinic.
Rates of both diabetes and pancreatic cancer are increasing in the United States, according to Wainberg.
"Pancreatic cancer is on the rise in the United States, and there are multiple theories why. But this is one of them: that the increased group of patients that are developing diabetes increases the risk of pancreatic cancer," he said.
Pancreatic cancer affects over 55,000 people in the United States every year. About 80% are diagnosed at a late stage, after the cancer has spread to other parts of the body, according to a 2015 study.
"By the time pancreatic cancer is found, it's almost always spread or it's to the point where it can't be removed successfully," Wainberg said. "It also has a tendency to spread very early compared to other cancers."
There are no reliable screening tests for pancreatic cancer, so identification of high-risk individuals earlier on could help increase survival, according to Setiawan.
"Very little is known about what the risk factors are for this very fatal cancer," Setiawan said. "So we tried to see if recent-onset diabetes could be used as an early marker for people who eventually develop pancreatic cancer."
The researchers looked exclusively at African-American and Hispanic individuals due to the high prevalence of diabetes in both populations, according to Wainberg.
"What makes this study unique is both the size of it and the fact that it focused pretty exclusively on minority patient populations in the United States," Wainberg said. "And this population is at higher risk of illnesses like diabetes, especially poorly controlled diabetes."
Though previous studies have shown an association between diabetes and pancreatic cancer, the new study's focus on high-risk populations is unique, according to Rushakoff.
"It is interesting to see that the increased association of pancreatic cancer is seen in these groups," Rushakoff said. "The prevalence of diabetes is high in these groups so confirming the association of diabetes and pancreatic cancer in these groups would be important."
The precise mechanisms linking diabetes with pancreatic cancer are still unclear.
"It's very bidirectional," Wainberg said. "For example, are these patients who have pancreatic cancer developing diabetes as a result of their cancer, or vice versa? Nobody is entirely sure."
The study only looked at two specific groups, meaning the results may not be able to be generalized to the entire population, according to Wainberg
But they suggest that those individuals who develop diabetes later in life might want to have a conversation with their physician about their risk for pancreatic cancer, he said.
"Based on this data, if you're a minority and you develop recent-onset diabetes, you should talk to your doctor about the implications of that for developing cancer, especially if you have any symptoms of pancreatic cancer," Wainberg said.