Doctors currently rely on MRI scans and other imaging techniques to diagnose brain tumors ― tests that aren’t typically part of a regular check up with your general practitioner.

A combination of headaches, memory loss, personality changes, blurred vision or slurred speech typically lead doctors to suspect, test for and eventually diagnose brain cancer, but by then it is often too late. By the time cancerous tumors cause those symptoms, they tend to be too aggressive to treat with drug therapies ― and treatments like surgery, radiation and chemotherapy are less effective than they would be in earlier stage cancers.

For some of the most common types of adult brain cancer, patients are only expected to live 14 months after being diagnosed.

Historically researchers have struggled to find better ways to diagnose brain cancer early because they don’t know what other signs to look for that suggest a cancer is growing.

But that may be shifting thanks to new research published earlier this month from a team at Ohio State University. They have identified a specific change in the body’s immune system that may be a predictor of the most common cancerous brain tumors ― gliomas ― five years before an individual develops symptoms.

“It was previously thought that glioblastoma (the most common type of adult glioma) appears more or less suddenly, without a precursor state,” said Judith Schwartzbaum, associate professor of epidemiology and lead researcher. Instead, there may be activity in the immune system that could signal a person is at a higher risk of developing brain cancer, she said.

The new data is significant because it’s one of the first known studies to look specifically at what’s happening to the immune system before a patient develops a glioma, Schwartzbaum explained. “Clinicians don’t see this period because patients don’t [typically get diagnosed] until they have symptoms.“

This type of blood test, along with other indicators (such as those from imaging or genetic tests), could help inform doctors which patients are at higher risk of developing cancerous brain tumors than others. This line of research could lead scientists to design treatments to block further tumor growth, Schwartzbaum added.

A big limitation of this new research is that it’s still not clear if this type of immune system activity is specific to gliomas, Schwartzbaum said. The immune system might, for example, show the same type of activity as a precursor to other cancers or diseases, too, she explained. And that means that the type of blood test the researchers used for this study is not likely to be specific enough to be used alone to diagnose brain cancer. But in the future it might help let your doctor know that you’re more likely to develop brain cancer than someone else ― and should be screened more often.

Blood tests for brain cancer may be possible, but more studies are needed

This research is still early in terms for being clinically useful, but it’s an important step on the path to finding ways to diagnose brain cancers earlier, Joe Wiemels, professor of epidemiology and biostatistics at the University of California San Francisco School of Medicine, told HuffPost.

“Brain cancer is usually diagnosed after significant neurological events and deficits,” said Wiemels, who was not involved in the new study. “This research suggests that a blood test may herald events occurring in the brain years prior to the clinical diagnosis of brain tumors.”

He suspects that one day a blood test alone may be able to diagnose brain cancer ― but a lot more research is needed before that happens. First studies are needed to verify these findings and also find more blood biomarkers for brain cancer, Wiemels said. He agreed with Schwatzbaum that cytokines ― proteins in the blood responsible for sending signals to each other and immune cells about when to attack potentially harmful cells ― alone are not specific enough by themselves to predict brain cancer, but along with specific DNA or other genetic signals (that have yet to be identified), such diagnostic tools could be designed.

It’s an exciting prospect as existing cancer treatments ― from immunotherapies to surgery to radiation to chemotherapy ― will all work better on tumors diagnosed when they are less advanced, he said.

“It may be possible to reverse such defects by manipulating immune function (immunotherapy) before the tumor grows too large,” Wiemels added.