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Background and Purpose: Previous analyses of target reproducibility in extracranial stereotactic radiotherapy have revealed standard security margins for planning target volume (PTV) definition of 5mm in axial and 5-10mm in longitudinal direction. In this study the reproducibility of the clinical target volume (CTV) of lung and liver tumors within the PTV over the complete course of hypofractionated treatment is evaluated. The impact of target mobility on dose to the CTV is assessed by dose-volume histograms (DVH)., Materials and Methods: Twenty-two pulmonary and 21 hepatic targets were treated with three stereotactic fractions of 10 Gy to the PTV-enclosing 100%-isodose with normalization to 150% at the isocenter. A conformal dose distribution was related to the PTV, which was defined by margins of 5-10mm added to the CTV. Prior to each fraction a computed tomography (CT)-simulation over the complete target volume was performed resulting in a total of 60 CT-simulations for lung and 58 CT-simulations for hepatic targets. The CTV from each CT-simulation was segmented and matched with the CT-study used for treatment planning. A DVH of the simulated CTV was calculated for each fraction. The target coverage (TC) of dose to the simulated CTV was defined as the proportion of the CTV receiving at least the reference dose (100%)., Results: A decrease of TC to <95% was found in 3/60 simulations (5%) of pulmonary and 7/58 simulations (12%) of hepatic targets. In two of 22 pulmonary targets (9%) and in four of 21 hepatic targets (19%) a TC of <95% occurred in at least one fraction. At risk for a decreased TC <95% were pulmonary targets with increased breathing mobility and hepatic targets with a CTV exceeding 100 cm(3)., Conclusions: Target reproducibility was precise within the reference isodose in 91% of lung and 81% of liver tumors with a TC of the complete CTV >or=95% at each fraction of treatment. Pulmonary targets with increased breathing mobility and liver tumors >100 cm(3) are at risk for target deviation exceeding the standard security margins for PTV-definition at least for one fraction and require individual evaluation of sufficient margins.

Background: Stereotactic irradiation of extracranial targets offers a non-invasive treatment modality for patients with localized tumors, which are not amenable for surgery or other invasive approaches because of age or impaired medical condition. The purpose of the study was the evaluation of the method to achieve local control of irradiated targets in relation to treatment toxicity., Patients and Methods: Irradiation was performed as hypofractionated treatment in three fractions of 10 Gy each, normalized to the PTV enclosing 65% isodose with patient fixation in a stereotactic body frame. The isocenter was localized by stereotactic coordinates. Targets were circumscribed tumors in the lung (n = 27) and liver (n = 24) not amenable for other treatment modalities: primary lung cancer (n = 12), local recurrences of lung cancer (n = 4), lung metastases (n = 11), liver metastases (n = 23) and one cholangiocellular carcinoma. Median CTV/PTV for targets in the lung was 57/113 cm3 (min/max 5-277 cm3/17-343 cm3) and for targets in the liver 50/102 cm3 (min/max 9-516 cm3/42-772 cm3). Median follow-up for targets in the lung was 8 months (2-33) and 9 months (2-28) for liver targets. Local control was defined as complete or partial remission and stable disease, measured by repeated CT scans after 6 weeks and in 3 months intervals. Treatment toxicity was evaluated according to the WHO score., Results: Crude local control was 85% for pulmonary targets and 83% for hepatic targets. Actuarial local control after 1 and 2 years was 76% and 76% for lung tumors and 76% and 61% for liver tumors. Actuarial overall patient survival was 48% after 1 year and 21% after 2 years for targets in the lung and 71% and 43% for targets in the liver. No acute grade 3-5 side effects were observed. Serious late toxicity occurred in two patients: a chronic ulceration of the esophagus at a target close to the mediastinum after 3 months (grade 3) and fatal bleeding from the pulmonary artery after 9 months (grade 5) in a previously irradiated patient. It remained unclear, whether the bleeding was a side effect of irradiation or due to tumor infiltration., Conclusion: Hypofractionated stereotactic irradiation of targets in the lung and liver is a locally effective treatment with actuarial local control rates of 76% after 1 year and 61-76% after 2 years without relevant acute toxicity. Severe late toxicity did not occur, if targets close to the mediastinum were avoided.