A promising new test based on genetic analysis may soon help doctors tell which prostate cancer patients have the best, and worst, chances of survival, scientists reported Monday.

By looking at cancer tissue to see if a gene called thymosin B15 is activated, it may be possible to determine which patients are in danger from their cancer spreading, or metastasizing. The patients in most danger might then be treated more aggressively.

The early experiments indicate the gene is involved in a phenomenon called cell motility, a cell’s ability to wiggle out of a tumor, enter the bloodstream and migrate to a distant site. Less motile cells tend to stay put, reducing the risk of spreading.

“If you knew this, you’d know which patients to treat aggressively with surgery and radiation, and which patients to monitor most closely,” said cell biologist Bruce Zetter. “So we’re continuing to test to see if our molecule can be predictive for the course of prostate cancer.”

Zetter and his colleagues work at Children’s Hospital in Boston, and the Harvard Medical School. Their results were reported Monday in the journal Nature Medicine.