Tomohisa Furuya1, Jun H Phua2, Mark Ruschin3, Hiroshi Tanaka4, Keiji Nihei5, Dilini Pinnaduwage6, Yu Kumazaki7, Masao Nakayama8, Hideki Nishimura9, Jason St-Hilaire10, Isabelle Thibault10, Daniel T Yat Harn2, Lijun Ma6, Naoto Shikama11, Arjun Sahgal3, Katsuyuki Karasawa5. 1. Department of Radiology, Tokyo Metropolitan Cancer and Infectious Diseases Center Komagome Hospital, Tokyo, Japan. Electronic address: tfuruya@cick.jp. 2. Department of Radiation Oncology, National Cancer Center Singapore, Singapore, Singapore. 3. Department of Radiation Oncology, Sunnybrook Odette Cancer Center, University of Toronto, Toronto, Ontario, Canada. 4. Department of Radiation Oncology, Aichi Cancer Center Hospital, Aichi, Japan. 5. Department of Radiology, Tokyo Metropolitan Cancer and Infectious Diseases Center Komagome Hospital, Tokyo, Japan. 6. Department of Radiation Oncology, University of California San Francisco, San Francisco, California. 7. Department of Radiation Oncology, Saitama Medical University, International Medical Center, Saitama, Japan. 8. Division of Radiation Oncology, Kobe University Graduate School of Medicine, Hyogo, Japan. 9. Department of Radiation Oncology, Kobe Minimally Invasive Cancer Center, Hyogo, Japan. 10. Department of Radiation Oncology, Centre Hospitalier Universitaire de Québec, Quebec City, Quebec, Canada. 11. Graduate School of Medicine Department of Radiation Oncology, Juntendo University, Tokyo, Japan.
Abstract
PURPOSE: This study aimed to assess the effectiveness of multiple dose-volume specifications in minimizing interinstitutional, target-prescribed, dose variations for spine stereotactic body radiation therapy (SBRT). METHODS AND MATERIALS: Seven institutions with a total of 10 treatment apparatuses participated in this study. SBRT plans for 3 representative spinal metastases were generated using 2 different protocols (Protocols 1 and 2) for target dose. While using just 2 target dose objectives (doses delivered to 95% and maximum point dose) in Protocol 1, 3 target dose constraints (doses delivered to 95% and 50% and maximum point dose) were defined in Protocol 2 with the intent to decrease target dose variation. A dose-volume histogram analysis was performed for the evaluated planning target volume (PTVevl) and critical neural structures such as the spinal cord and cauda equina. RESULTS: Doses to the organs at risk were all maintained at the maximal tolerance in both protocols; however, the interinstitutional variation of the PTVevl dose-volume histograms was significantly decreased with Protocol 2. Furthermore, the mean PTVevl covered by the prescription dose was increased from 73.0% in Protocol 1 to 85.8% in Protocol 2. There were no differences in the mean values of the nearly maximum dose of the critical neural structures between 2 protocols. CONCLUSIONS: In spine SBRT with the emphasis on preservation of critical neural structures, the target prescribed dose should be defined by using multiple dose-volume objectives to minimize user and apparatus-dependent dose variabilities for the spinal metastases that are adjacent to the critical neural structures.
PURPOSE: This study aimed to assess the effectiveness of multiple dose-volume specifications in minimizing interinstitutional, target-prescribed, dose variations for spine stereotactic body radiation therapy (SBRT). METHODS AND MATERIALS: Seven institutions with a total of 10 treatment apparatuses participated in this study. SBRT plans for 3 representative spinal metastases were generated using 2 different protocols (Protocols 1 and 2) for target dose. While using just 2 target dose objectives (doses delivered to 95% and maximum point dose) in Protocol 1, 3 target dose constraints (doses delivered to 95% and 50% and maximum point dose) were defined in Protocol 2 with the intent to decrease target dose variation. A dose-volume histogram analysis was performed for the evaluated planning target volume (PTVevl) and critical neural structures such as the spinal cord and cauda equina. RESULTS: Doses to the organs at risk were all maintained at the maximal tolerance in both protocols; however, the interinstitutional variation of the PTVevl dose-volume histograms was significantly decreased with Protocol 2. Furthermore, the mean PTVevl covered by the prescription dose was increased from 73.0% in Protocol 1 to 85.8% in Protocol 2. There were no differences in the mean values of the nearly maximum dose of the critical neural structures between 2 protocols. CONCLUSIONS: In spine SBRT with the emphasis on preservation of critical neural structures, the target prescribed dose should be defined by using multiple dose-volume objectives to minimize user and apparatus-dependent dose variabilities for the spinal metastases that are adjacent to the critical neural structures.