Abstract
We investigated the technique, early results and toxicity of curative stereotactic radiotherapy with the CyberKnife® (Accuray Incorporated, Sunnyvale, California, USA) in 15 extracranial, extrapulmonary, extrahepatic, and extraspinal tumors. Fourteen tumors were located close to the bowel or esophagus. The PTV = GTV + 2–5 mm. The dose to the tumors varied from 10 fractions of 4 Gy up to 3 fractions of 20 Gy (median dose/fraction: 7 Gy; median number of fractions: 6), and depended on the proximity of the bowel. A small volume of the bowel was allowed to receive a dose of 6 Gy/fraction. The dose to the PTV was prescribed to the 75–85% isodose line. With a median follow up of 18 months, the 2-year local control and overall survival was 100%. Due to our flexible fractionation schedules, we were able to prescribe the dose to at least 90% of the PTV (median 95%) without increasing the dose to the bowel > 6 Gy/fraction. Five acute side effects were seen in four patients: two patients had transient grade 1 lymph edema in the leg, one patient complained of grade 1 pain in the abdomen and diarrhea, and one patient complained of grade 1 radiation dermatitis. Late toxicity such as grade 1 rectal bleeding, grade 1 diarrhea, grade 2 painful subcutaneous fibrosis, grade 2 pain in a surgical scar on the abdominal wall and an asymptomatic occlusion of the ureter was observed. Curative stereotactic radiotherapy treatment with the CyberKnife for extracranial, extrapulmonary, extrahepatic, and extraspinal, locally recurrent or solitary metastatic tumors is feasible and results in excellent local control and survival with low acute and late toxicity. A small volume of the bowel is able to tolerate a dose of 6 Gy per fraction for a maximum of 6 fractions.