Stereotactic radiotherapy of primary liver cancer and hepatic metastases.

The purpose was to evaluate the clinical results of stereotactic radiotherapy in primary liver tumors and hepatic metastases. Five patients with primary liver cancer and 39 patients with 51 hepatic metastases were treated by stereotactic radiotherapy since 1997. Twenty-eight targets were treated in a "low-dose"-group with 3 x 10 Gy (n = 27) or 4 x 7 Gy (n = 1) prescribed to the PTV-encl. 65%-isodose. In a "high-dose"-group patients were treated with 3 x 12 - 12.5 Gy (n = 19; same dose prescription) or 1 x 26 Gy/PTV-enclosing 80%-isodose (n = 9). Median follow-up was 15 months (2-48 months) for primary liver cancer and 15 months (2-85 months) for hepatic metastases. While all primary liver cancers were controlled, nine local failures (3-19 months) of 51 metastases were observed resulting in an actuarial local control rate of 92% after 12 months and 66% after 24 months and later. A borderline significant correlation between dose and local control was observed (p = 0.077): the actuarial local control rate after 12 and 24 months was 86% and 58% in the low-dose-group versus 100% and 82% in the high-dose-group. In multivariate analysis high versus low-dose was the only significant factor predicting local control (p = 0.0089). Overall survival after 1 and 2 years was 72% and 32% for all patients and was impaired due to systemic progression of disease. No severe acute or late toxicity exceeding RTOG/EORTC-score 2 were observed. Stereotactic irradiation of primary liver cancer and hepatic metastases offers a locally effective treatment without significant complications in patients, who are not amenable for surgery. Patient selection is important, because those with low risk for systemic progression are more likely to benefit from this approach.

Influence of calculation model on dose distribution in stereotactic radiotherapy for pulmonary targets.

PURPOSE: To compare the pencil beam (PB) and collapsed cone (CC)-based three-dimensional dose calculation used for stereotactic irradiation of pulmonary targets. METHODS AND MATERIALS: Three-dimensional conformal dose distributions (using 6-MV and 18-MV photon beams) were generated for 33 pulmonary targets using the PB algorithm implemented in the Helax-TMS treatment planning system and then recalculated with the CC algorithm of TMS using an identical beam setup and parameters. The differences were analyzed by evaluating the dose-volume histograms for the planning target volume (PTV) and clinical target volume (CTV) and evaluating the computed absolute monitor units (MUs). The influence of the photon energy was also studied. For three cases, the results were compared with Monte-Carlo calculations. RESULTS: Use of the CC model typically showed increased dose inhomogeneity. Owing to a more accurate modeling of secondary charged particle disequilibrium at the tumor-lung interface, the beam penumbra is broadened. The median and mean target dose decreased by 13.9% and 11.2% for the PTV and 9.2% and 9.4% for the CTV, respectively, using the CC algorithm. Consequently, the average PTV dose coverage decreased by 7.1% (SD, 6.5%). On average, the MUs calculated to achieve the prescribed dose were 5.4% (SD, 5.8%) greater for the CC algorithm. The difference in MUs between the PB and CC increased with decreasing PTV size and high photon energy (18 MV; r = -0.68), reaching 26% at the maximum. CONCLUSION: The absorbed dose at the lung-tumor interface calculated by the PB algorithm was considerably greater than the dose calculated using the CC algorithm. In small targets (PTV < or = 100 cm(3)) and for 18-MV photons, the MUs calculated with PB may lead to an insufficient dose to the target volume.

Influence of calculation algorithm on dose distribution in irradiation of non-small cell lung cancer (NSCLC) collapsed cone versus pencil beam.

PURPOSE: . The influence of two different calculation algorithms ("pencil beam" [PB] versus "collapsed cone" [CC]) on dose distribution, as well as the dose-volume histograms (DVHs) of the planning target volume (PTV) and the organs at risk was analyzed for irradiation of lung cancer. MATERIAL AND METHODS: . Between 10/2001 and 02/2002 three-dimensional treatment planning was done in ten patients with lung cancer (Helax, TMS((R)), V.6.01). The PTV, the ipsilateral lung (IL) and the contralateral lung (CL) were defined in each axial CT slice (slice thickness 1 cm). Dose distributions for three-dimensional multiple-field technique were calculated using a PB and a CC algorithm, respectively. Normalization was in accordance with ICRU 50. The DVHs were analyzed relating the minimum, maximum, median and mean dose to the volumes of interest (VOI). RESULTS: . Median PTV amounted to 774 cm(3). Minimum dose within the PTV was 67.4% for CC and 75.6% for PB algorithm (p = 0.04). Using the CC algorithm, only 76.5% of the PTV was included by the 95% isodose, whereas 90.1% was included when the PB algorithm (p = 0.01) was used. Median volume of IL amounted to 1 953 cm(3). Mean dose to IL was 43.0% for CC and 44.0% for PB algorithm (p = 0.02). Median volume of IL within the 80% isodose was 19.6% for CC and 24.1% for PB algorithm (p < 0.01). Median volume of CL amounted to 1 847 cm(3). Mean dose to CL was 17.4% for CC and 18.1% for PB algorithm (p < 0.01). Volume of CL within the 80% isodose was 3.3% for CC and 4.1% for PB algorithm (p = 0.03). CONCLUSION: . The CC and PB calculation algorithms result in different dose distributions in case of lung tumors. Particularly the minimum dose to the PTV, which may be relevant for tumor control, is significantly lower for CC. Since it is generally accepted that the CC algorithm describes secondary particle transport more exactly than PB models, the use of the latter should be critically evaluated in the treatment planning of lung cancer.

Stereotactic radiotherapy for primary lung cancer and pulmonary metastases: a noninvasive treatment approach in medically inoperable patients.

PURPOSE: The clinical results of dose escalation using stereotactic radiotherapy to increase local tumor control in medically inoperable patients with Stage I-II non-small-cell lung cancer or pulmonary metastases were evaluated. METHODS AND MATERIALS: Twenty patients with Stage I-II non-small-cell lung cancer and 41 patients with 51 pulmonary metastases not amenable to surgery were treated with stereotactic radiotherapy at 3 x 10 Gy (n = 19), 3 x 12-12.5 Gy to the planning target volume enclosing 100%-isodose, with normalization to 150% at the isocenter; n = 26) or 1 x 26 Gy to the planning target volume enclosing 80%-isodose (n = 26). The median follow-up was 11 months (range, 2-61 months) for primary lung cancer patients and 9 months (range, 2-37 months) for patients with metastases. RESULTS: The actuarial local control rate was 92% for lung cancer patients and 80% for metastasis patients > or =1 year after treatment and was significantly improved by increasing the dose from 3 x 10 Gy to 3 x 12-12.5 Gy or 1 x 26 Gy (p = 0.038). The overall survival rate after 1 and 2 years was 52% and 32%, respectively, for lung cancer patients and 85% and 33%, respectively, for metastasis patients, impaired because of systemic disease progression. After 12 months, 60% of patients with primary lung cancer and 35% of patients with pulmonary metastases were without systemic progression. No severe acute or late toxicity was observed, and only 2 patients (3%) developed symptomatic Grade 2 pneumonitis, which was successfully treated with oral steroids. CONCLUSION: Stereotactic radiotherapy for lung tumors offers a very effective treatment option locally without significant complications in medically impaired patients who are not amenable to surgery. Patient selection is important, because those with a low risk of systemic progression are more likely to benefit from this approach.