A new test that looks at immune cells in the lymph nodes may be the best way to predict whether Breast cancer has spread and will be likely to recur, doctors said on Monday.

Currently, the best way to predict whether Breast cancer is likely to come back is to search for tumor cells in the lymph nodes near the breast.

But Dr. Peter Lee and colleagues at the Stanford University School of Medicine say that perhaps examining the immune cells in those lymph nodes might be a better way to predict the cancer’s spread.

Patients whose tests suggest an aggressive cancer could receive extra treatment to try to kill any stray tumor cells.

“Immune changes in the lymph node almost perfectly predict clinical outcome, much better than any other prognostic factor that is available today,” Lee said in a statement.

Writing in the journal Public Library of Science-Medicine, Lee and colleagues said they tested lymph node tissue samples from 77 Breast cancer patients taken more than five years ago. All of these patients had had cancer that had spread out of the breast.

Within five years, 33 of the 77 patients had their cancer return.

Immune cells are known to sometimes destroy cancer cells - they keep cancer constantly under control in most normal healthy people. But Lee was tying to find out what goes wrong when the immune system fails to control cancer.

Lee’s team looked for tumor cells and for three major types of immune cells: cytotoxic T cells, helper T cells and dendritic cells.

Lymph nodes that had been invaded by tumor cells showed dramatic decreases in helper T cells and dendritic cells. They also had fewer cytotoxic T cells, Lee found.

“Then we found something more interesting and puzzling,” Lee said. Even in some lymph nodes that had only a few tumor cells, or no tumor cells, the immune cell balance was off.

For the most part, this imbalance in immune cells was seen in the 33 women whose Breast cancer came back before five years, Lee’s team found.

“It was a surprise to find immune changes in lymph nodes with no detectable tumor cells,” said Lee.

Perhaps tumor cells secrete some substance that prepares the lymph node for invasion, he said. “Even before it actually invades the node, it actually causes the node to change,” he added.

The women whose lymph nodes had a normal immune cell balance had an 85 to 90 percent chance of being disease-free after five years. The group with an “unfavorable” immune profile had less than a 15 percent chance, Lee’s team reported.

Lee hopes to develop a simple test that could help determine which women could benefit from more aggressive therapy, and which could be spared undergoing costly and toxic treatments unnecessarily.