Extracranial stereotactic radiation therapy: Set-up accuracy of patients treated for liver metastases

Purpose: Patients with liver metastases might benefit from high-dose confor mal radiation therapy. A high accuracy of repositioning and a reduction of target movement are necessary for such an approach. The set-up accuracy of patients with liver metastases treated with stereotactic single dose radiat ion was evaluated. Methods and Materials: Twenty-four patients with liver metastases were trea ted with single dose radiation therapy on 26 occasions using a self-develop ed stereotactic frame. Liver movement was reduced by abdominal pressure, Th e effectiveness was evaluated under fluoroscopy, CT scans were performed on the planning day and directly before treatment. Representative reference m arks were chosen and the coordinates were calculated. In addition, the targ et displacement was quantitatively evaluated after treatment. Results: Diaphragmal movement was reduced to median 7 mm (range: 3-13 mm). The final set-up accuracy of the body was limited to all of median 1.8 mm i n latero-lateral direction (range: 0.3-5.0 mm) and 2.0 mm in anterior-poste rior direction (0.8-3.8 mm), Deviations of the body in cranio-caudal direct ion were always less than the thickness of one CT slice (<5 mm). However, a repositioning was necessary in 16 occasions. The final target shift was me dian 1.6 mm (0.2-7.0 mm) in latero-lateral and 2.3 mm in anterior-posterior direction (0.0-6.3 mm), The median shift in cranio-caudal direction was 4. 4 mm (0.0-10.0 mm), Conclusions: In patients with liver metastases, a high set-up accuracy of t he body and the target can be achieved. This allows a high-dose focal radio therapy of these lesions. However, a control CT scan should be performed di rectly before therapy to confirm set-up accuracy and possibly prompt necess ary corrections. (C) 2000 Elsevier Science Inc.