What are the biggest risks of radiation surgery?

Depends. Varies on the organ system having surgery or radiation.
Injure normal tissue. Radiation surgery (rs) is refinement of radiation treatment (rt), which has existed for many years. Bottom-line:chemotherapy and rt is designed to destroy, hoping we would destroy cancer cells before the patient. This means that unfortunately, some innocent by-stander healthy tissue will be affected, including skin on the treatment site. Surgery allows how much disease we have removed;rs will not.