FRIDAY, Sept. 18, 2015 (HealthDay News) -- Brain tumors known as gliomas usually produce symptoms several months before they're diagnosed, but new research found changes in immune function may occur up to five years before these cancers are detected.
"Now, clinicians don't have any way to detect the tumors until patients have symptoms, which is typically three months before diagnosis. I see something five years before," study author Judith Schwartzbaum, an associate professor of epidemiology at Ohio State University, in Columbus.
Researchers analyzed blood samples collected over 40 years in Norway from people getting annual checkups or donating blood. Norway also has a cancer registry, enabling the researchers to identify blood samples of people who developed a brain tumor. The blood samples were collected an average of 15 years before tumors were detected.
Specifically, the researchers compared interactions between 12 allergy-related proteins, called cytokines, in the blood samples of 487 people diagnosed with glioma and 487 samples from people without cancer.
Cytokines are activated during an allergy-related immune response. Allergies, the study authors noted, have been linked to reduced risk for glioma.
At first, the study revealed no significant differences among the blood samples. But after limiting the analysis to 55 people who gave blood no more than five years before they were diagnosed with a brain tumor, the researchers found reduced interaction among cytokines compared to otherwise healthy people, they reported in the Sept. 9 issue of PLOS ONE.
Gliomas can suppress the immune system, which enables them to grow. Early on, these tumors can cause detectable changes in the immune system long before the disease is diagnosed, the researchers explained.
"The cytokines are not signaling as strongly to each other as the time of diagnosis approaches. Mathematicians who have modeled immune function changes in glioma patients suggest this means the tumor is starting to direct or suppress local immune activation. And that makes sense," Schwartzbaum said in a university news release.
"I can't say which are the most important cytokines because they're all related to each other and they don't act alone. But I see a weakening of all of their relationships in glioma patients within five years before diagnosis, and nothing like that among controls," she said.
The researchers pointed out that higher levels of the protein IL4, which is overproduced in people with allergies, is linked to a lower risk for glioma later in life. They suggested allergies could help protect against these brain tumors up to 20 years before they might develop.
However, the researchers said they're still not sure whether allergies reduce cancer risk or if these tumors interfere with the immune response to allergens.
Glioblastomas, the most serious form of glioma, account for 60 percent of adult brain tumors in the United States, affecting an estimated five in 100,000 people, the researchers said. On average, patients treated with surgery, radiation and chemotherapy survive for about one year after diagnosis. Less than 10 percent of patients survive up to five years, the researchers added.
The U.S. National Cancer Institute provides more on brain tumors.