- Radio-opaque markers must be present within the tumor bed. In patients who have undergone surgical resection, radio-opaque surgical clips within the tumor bed can be used as fiducials. Patients without surgical clips in the tumor bed must be able to have fiducials placed endoscopically, laparoscopically, or through a CT- or ultrasound-guided technique. If not, the tumor must be posterior and adjacent to the aorta, and treatment will only be permitted at the discretion of the Principal Investigator.