By linking high water movement in tumors to positive drug response, the UCLA team predicted with 70 percent accuracy which patients' tumors were the least likely to grow six months after therapy.
The powerful drug Avastin shrinks tumors by choking off their blood supply. Half of patients don't respond to the therapy, though, exposing them to unnecessary side effects and medication costing up to $10,000 per month.
Now UCLA scientists have uncovered a new way to image tumors and forecast which patients are most likely to benefit from Avastin before starting a single dose of treatment.
The UCLA team studied 82 patients who had undergone surgery and radiation therapy to remove glioblastoma, the most common and deadly form of adult brain tumor. Half of the patients received infusions of Avastin every two weeks. All underwent monthly brain scans by magnetic resonance imaging (MRI) to monitor change.
Cancer cells secrete a growth factor called VEGF that spurs the growth of new blood vessels to supply the tumor with oxygen and nutrients. Avastin blocks VEGF, essentially starving the tumor to death.
This process launches a chain of events that is detectable by MRI. Oxygen-starved cells produce more VEGF, which causes blood vessels to leak fluids into the tumor and surrounding tissue. This results in swelling, which boosts water's ability to move freely in the tumor and brain tissue. As cells disintegrate, they no longer pose a physical barrier to water movement.
"We theorized that tumors with more water motion would also have higher VEGF levels," explained Whitney Pope, assistant professor of radiological sciences. "Because Avastin targets VEGF, it made sense that the drug would work better in tumors with high levels of the growth factor."
By measuring the amount of water motion within the tumor, the researchers were able to predict with 70 percent accuracy which patients' tumors would progress within six months and which would not. They detected greater water movement in the tumors of those persons who later responded best to Avastin.
MEDICA.de; Source: University of California, Los Angeles