RefleXion is a privately-held company developing the first biology-guided radiotherapy system, a significant change in strategy from single tumor therapy to the ability to one day treat multiple tumors in the same treatment session in cancers that have metastasized. Currently, the RefleXion X1 machine is cleared for the delivery of stereotactic body radiotherapy (SBRT), stereotactic radiosurgery (SRS) and intensity modulated radiotherapy (IMRT). The company is also developing BgRT, which incorporates positron-emission tomography (PET) imaging data to enable tumors to continuously signal their location. The BgRT technology will synchronize these data with the linear accelerator to direct radiotherapy to tumors with subsecond latency.