Planning benchmark study for SBRT of early stage NSCLC : Results of the DEGRO Working Group Stereotactic Radiotherapy.

PURPOSE: The aim was to evaluate stereotactic body radiation therapy (SBRT) treatment planning variability for early stage nonsmall cell lung cancer (NSCLC) with respect to the published guidelines of the Stereotactic Radiotherapy Working Group of the German Society for Radiation Oncology (DEGRO). MATERIALS AND METHODS: Planning computed tomography (CT) scan and the structure sets (planning target volume, PTV; organs at risk, OARs) of 3 patients with early stage NSCLC were sent to 22 radiotherapy departments with SBRT experience: each department was asked to prepare a treatment plan according to the DEGRO guidelines. The prescription dose was 3 fractions of 15 Gy to the 65% isodose. RESULTS: In all, 87 plans were generated: 36 used intensity-modulated arc therapy (IMAT), 21 used three-dimensional conformal radiation therapy (3DCRT), 6 used static field intensity-modulated radiation therapy (SF-IMRT), 9 used helical radiotherapy and 15 used robotic radiosurgery. PTV dose coverage and simultaneously kept OARs doses were within the clinical limits published in the DEGRO guidelines. However, mean PTV dose (mean 58.0 Gy, range 52.8-66.4 Gy) and dose conformity indices (mean 0.75, range 0.60-1.00) varied between institutions and techniques (p ≤ 0.02). OARs doses varied substantially between institutions, but appeared to be technique independent (p = 0.21). CONCLUSION: All studied treatment techniques are well suited for SBRT of early stage NSCLC according to the DEGRO guidelines. Homogenization of SBRT practice in Germany is possible through the guidelines; however, detailed treatment plan characteristics varied between techniques and institutions and further homogenization is warranted in future studies and recommendations. Optimized treatment planning should always follow the ALARA (as low as reasonably achievable) principle.

[A quantitative study of MRI-based treatment planning for the percutaneous radiation therapy of brain tumors]. / Eine quantitative Studie zur MRT-basierten Bestrahlungsplanung der perkutanen Therapie von Hirntumoren.

This study examined to which extent treatment plans for brain tumors can be constructed with a commercial treatment planning system (TPS) based on MRI data only. CadPlan 6.4.7 was used as TPS. In particular, differences between MRT-based and conventional CT-based plans were examined systematically. The quantification of the retrospective evaluation was carried out by the point-wise dose difference and the gamma-distribution. In this study the gamma-distribution did not appear advantageous over the dose difference for the tolerance range (point-wise dose difference < 3%, distance criterion LLL 5 mm). The calculated dose distribution showed large differences (up to 103%) at the boundary of the treatment fields, in the regions of the head contour, and in areas with air inclusions and significant bone structures. The inner parts of the fields, and therefore the actual target volume, revealed only small deviations in the range of-2% in the homogeneous distribution.