C Katharina Spindeldreier1,2,3, Sebastian Klüter1,2,3, Philipp Hoegen1,2,3, Carolin Buchele1,2,3, Carolin Rippke1,2,3, Eric Tonndorf-Martini1,2,3, Jürgen Debus1,2,3,4,5, Juliane Hörner-Rieber6,7,8,9. 1. Department of Radiation Oncology, Heidelberg University Hospital, Im Neuenheimer Feld 400, 69120, Heidelberg, Germany. 2. Heidelberg Institute of Radiation Oncology (HIRO), Heidelberg, Germany. 3. National Center for Tumor diseases (NCT), Heidelberg, Germany. 4. Heidelberg Ion-Beam Therapy Center (HIT), Department of Radiation Oncology, Heidelberg University Hospital, Heidelberg, Germany. 5. Clinical Cooperation Unit Radiation Oncology, German Cancer Research Center (DKFZ), Heidelberg, Germany. 6. Department of Radiation Oncology, Heidelberg University Hospital, Im Neuenheimer Feld 400, 69120, Heidelberg, Germany. juliane.hoerner-rieber@med.uni-heidelberg.de. 7. Heidelberg Institute of Radiation Oncology (HIRO), Heidelberg, Germany. juliane.hoerner-rieber@med.uni-heidelberg.de. 8. National Center for Tumor diseases (NCT), Heidelberg, Germany. juliane.hoerner-rieber@med.uni-heidelberg.de. 9. Clinical Cooperation Unit Radiation Oncology, German Cancer Research Center (DKFZ), Heidelberg, Germany. juliane.hoerner-rieber@med.uni-heidelberg.de.
Abstract
INTRODUCTION: Hybrid magnetic resonance (MR) linear accelerators (MR-Linacs) for radiotherapy allow for the visualization and tracking of moving target volumes during the entire treatment. This makes gated treatments possible, decreasing the irradiated volumes and thus sparing healthy tissue from unnecessary radiation dose. Conventionally, tumors that are subject to respiration motion are treated by irradiating the entire area of potential target presence (internal target volume, ITV). This study presents three patient cases (lung, adrenal gland, and liver tumors) treated with gated MR-guided radiotherapy and compares the treatment plans retrospectively with conventional ITV plans. MATERIALS AND METHODS: The gross tumor volume was delineated on MR and computed tomography (CT) images of the patients, and MR-Linac treatment plans were generated using additional clinical and planning target volume margins. The motion of the gross tumor volume was evaluated on two-dimensional cine-MRI images during the entire MR-Linac treatment. Based on the motion analysis, standard ITV-based plans were retrospectively created and compared by means of irradiated target volumes and dose-volume parameters. RESULTS: For the MR-Linac plans, the irradiated treatment volumes were reduced by an average of 62% across the three cases, and for one case the ITV-based target volume would have overlapped with a critical organ. Target volume coverage was much better and the lung and adrenal MR-Linac plans revealed superior sparing of the organs at risks thanks to gated treatments. CONCLUSION: Dosimetrically beneficial treatment plans with promising clinical outcomes can be applied when using gated MR-guided radiotherapy. Future studies will reveal which patients will benefit most from this technique. To utilize the full potential of online adaptive, individualized MR-guided therapy, the close collaboration of radio-oncology and radiology is needed.
INTRODUCTION: Hybrid magnetic resonance (MR) linear accelerators (MR-Linacs) for radiotherapy allow for the visualization and tracking of moving target volumes during the entire treatment. This makes gated treatments possible, decreasing the irradiated volumes and thus sparing healthy tissue from unnecessary radiation dose. Conventionally, tumors that are subject to respiration motion are treated by irradiating the entire area of potential target presence (internal target volume, ITV). This study presents three patient cases (lung, adrenal gland, and liver tumors) treated with gated MR-guided radiotherapy and compares the treatment plans retrospectively with conventional ITV plans. MATERIALS AND METHODS: The gross tumor volume was delineated on MR and computed tomography (CT) images of the patients, and MR-Linac treatment plans were generated using additional clinical and planning target volume margins. The motion of the gross tumor volume was evaluated on two-dimensional cine-MRI images during the entire MR-Linac treatment. Based on the motion analysis, standard ITV-based plans were retrospectively created and compared by means of irradiated target volumes and dose-volume parameters. RESULTS: For the MR-Linac plans, the irradiated treatment volumes were reduced by an average of 62% across the three cases, and for one case the ITV-based target volume would have overlapped with a critical organ. Target volume coverage was much better and the lung and adrenal MR-Linac plans revealed superior sparing of the organs at risks thanks to gated treatments. CONCLUSION: Dosimetrically beneficial treatment plans with promising clinical outcomes can be applied when using gated MR-guided radiotherapy. Future studies will reveal which patients will benefit most from this technique. To utilize the full potential of online adaptive, individualized MR-guided therapy, the close collaboration of radio-oncology and radiology is needed.
Authors: Kathryn Mittauer; Bhudatt Paliwal; Patrick Hill; John E Bayouth; Mark W Geurts; Andrew M Baschnagel; Kristin A Bradley; Paul M Harari; Stephen Rosenberg; Jeffrey V Brower; Andrzej P Wojcieszynski; Craig Hullett; R A Bayliss; Zacariah E Labby; Michael F Bassetti Journal: Cureus Date: 2018-04-04