Radiosurgery: Becoming the Treatment of Choice for Spinal Metastases More than 90 percent of spine tumors are metastatic. They begin somewhere else. Then a small number of cells break loose from the original tumor, enter the blood stream and travel to the spine. “Spine mets require aggres- sive management,” said Sean P. Pitroda, MD, assistant pro- fessor of radiation and cellular oncology and a researcher in the University of Chicago’s Ludwig Center for Metastasis Research. “Radiosurgery is currently the best way to treat this, to deliver a very high dose to a really small area.” Radiosurgery uses high doses of radiation with the precision of microsurgery—but no incision. The process begins with an injection of dye into the thecal sac, a tube that encases the spinal cord. This enables the team to map out the precise location of the spinal cord as it passes through the affected vertebra and, thus, avoid exposing the sensitive, easily damaged cord to radiation. During therapy, the radiation beam is modulated by 120 tiny collimators, thin metal leaves that are programmed to guide the radiation beams, each a few mil- limeters wide. They move “like little fingers, in and out to shape the beam in a complex way that leads to maximum tumor-cell kill,” Pitroda said. “That, and lots of planning, is how we adminis- ter high doses to the tumor while preventing the beams from hitting healthy structures, such as the spinal cord.” Smaller doses target tumor cells, primarily damaging their DNA. The larger doses can have the same effect, but they are also thought to damage the blood vessels that feed the tumor and activate an immune response to fight off tumor cells. “Spine mets require aggressive management. Radiosurgery is currently the best way to treat this, to deliver a very high dose to a really small area.” — Sean P. Pitroda, MD 20 Powered by Innovation