Blood Type, Pancreatic Cancer Risk Linked

March 10, 2009 -- People with blood types A, B, or AB are at higher risk of pancreatic cancer than those with type O, according to a new study.

Using data from two large groups of people, Brian Wolpin, MD, of the Dana-Farber Cancer Institute in Boston, and colleagues report finding what seems to be an association between blood types and risk of pancreatic cancer.

The study is published in the Journal of the National Cancer Institute.

The researchers examined data from 107,503 people who participated in either the Nurses' Health Study or the Health Professionals Follow-Up Study. The study started in 1996, and after an average follow-up period of nearly nine years, 316 study participants developed pancreatic cancer.

The researchers found that the age-adjusted incidence rate of pancreatic cancer for people with blood type O was significantly less than for individuals with A, AB, or B blood types.

Compared to participants with type O blood, those with type A blood were 32% more likely to develop pancreatic cancer. Those with type AB blood were 51% more likely, and those with type B were 72% more likely. These findings took into account known risk factors for pancreatic cancer such as age, obesity, smoking status, and family history of pancreatic cancer in a first-degree relative.

"The highest risk was observed for participants with blood group B, and intermediate risks were observed for those with blood groups A and AB," the researchers write.

There was no association seen between Rh type and risk for pancreatic cancer. Rh type refers to the "positive" or "negative" that helps characterize your blood type. For example, a person may be A positive or A negative.

"In two large, independent prospective cohorts, we observed a statistically elevated risk for incident pancreatic cancer among participants with blood group antigens A or B compared with those with blood group O," the researchers write. "Additional investigation is necessary to further confirm these findings and to determine the potential mechanisms" that might be responsible for the elevated risk.

An association between blood types and pancreatic cancer has been suspected, the researchers say, and their study adds fuel to this notion, but more research is needed.