Gated Volumetric-Modulated Arc Therapy vs. Tumor-Tracking CyberKnife Radiotherapy as Stereotactic Body Radiotherapy for Hepatocellular Carcinoma: A Dosimetric Comparison Study Focused on the Impact of Respiratory Motion Managements

PLOS ONE, Dec 2019

Purpose To assess the potential dosimetric benefits associated with the CyberKnife (CK) tumor tracking capability, wherein an extra margin for respiratory tumor motion is not required, when compared to respiratory-gated volumetric-modulated arc therapy (VMAT) for hepatocellular carcinoma (HCC). Methods Twenty-nine HCC patients previously treated with double-arc VMAT were enrolled. In each VMAT plan, the individual internal target volume (ITV) margin around the tumor was determined by measuring its motion over 30–70% of respiratory phases using four-dimensional computed tomography, followed by a 5-mm isotropic margin for the planning target volume (PTV). For each VMAT plan, two CK plans were generated using the original (CKoriginal, ITV included) and modified PTVs (CKmodified, ITV excluded) for comparison. In each case, the CKoriginal and CKmodified plans were compared to the original VMAT plan in terms of the dosimetric parameters including the conformity index (CI), PTV coverage (CO), organs at risk (OAR) doses, and normal liver tissue sparing. Results The original PTVs with median 24 cc (range, 9–65 cc) were significantly reduced to median 12 cc (range, 5–41 cc) in the CKmodified plans. Statistically significant differences in plan qualities were observed between the VMAT and the CK plans: mean CI, 1.05 in VMAT vs. 1.17 in both CK plans (p < 0.001); and mean CO, 93.0% in VMAT vs. 96.6% in CKoriginal and 96.9% in CKmodified (p < 0.001). The average volume of normal liver tissue receiving > 15 Gy was significantly decreased in the CKmodified plan, as compared to that in the VMAT and CKoriginal plans, by 1.75- and 1.61-fold, respectively. Conclusions The tumor tracking capability of the CK system can significantly decrease the volume of normal liver tissue receiving > 15 Gy, while maintaining high precision in target localization, conformity, tumor coverage, and dose sparing of the OAR. Therefore, it can be a valuable SBRT option, particularly for HCC patients with poor liver function.

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Gated Volumetric-Modulated Arc Therapy vs. Tumor-Tracking CyberKnife Radiotherapy as Stereotactic Body Radiotherapy for Hepatocellular Carcinoma: A Dosimetric Comparison Study Focused on the Impact of Respiratory Motion Managements

November Gated Volumetric-Modulated Arc Therapy vs. Tumor-Tracking CyberKnife Radiotherapy as Stereotactic Body Radiotherapy for Hepatocellular Carcinoma: A Dosimetric Comparison Study Focused on the Impact of Respiratory Motion Managements KyoungJun Yoon 0 1 Jungwon Kwak 0 1 Byungchul Cho 0 1 Jin-hong Park 0 1 Sang Min Yoon 0 1 Sang-wook Lee 0 1 Jong Hoon Kim 0 1 0 Department of Radiation Oncology, Asan Medical Center, University of Ulsan College of Medicine , Seoul , Republic of Korea 1 Editor: Do Young Kim, Yonsei University College of Medicine , REPUBLIC OF KOREA Twenty-nine HCC patients previously treated with double-arc VMAT were enrolled. In each VMAT plan, the individual internal target volume (ITV) margin around the tumor was determined by measuring its motion over 30±70% of respiratory phases using four-dimensional computed tomography, followed by a 5-mm isotropic margin for the planning target volume (PTV). For each VMAT plan, two CK plans were generated using the original (CKoriginal, ITV included) and modified PTVs (CKmodified, ITV excluded) for comparison. In each case, the CKoriginal and CKmodified plans were compared to the original VMAT plan in terms of the dosimetric parameters including the conformity index (CI), PTV coverage (CO), organs at risk (OAR) doses, and normal liver tissue sparing. The original PTVs with median 24 cc (range, 9±65 cc) were significantly reduced to median 12 cc (range, 5±41 cc) in the CKmodified plans. Statistically significant differences in plan qualities were observed between the VMAT and the CK plans: mean CI, 1.05 in VMAT vs. 1.17 in both CK plans (p < 0.001); and mean CO, 93.0% in VMAT vs. 96.6% in CKoriginal and 96.9% in CKmodified (p < 0.001). The average volume of normal liver tissue receiving > 15 Gy - Data Availability Statement: All relevant data are within the paper and its Supporting Information files. Funding: This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2014R1A1A2058154), and by the Radiation Technology R&D program (2013M2A2A7043506) Purpose Methods To assess the potential dosimetric benefits associated with the CyberKnife (CK) tumor tracking capability, wherein an extra margin for respiratory tumor motion is not required, when compared to respiratory-gated volumetric-modulated arc therapy (VMAT) for hepatocellular carcinoma (HCC). Results through the National Research Foundation of Korea funded by the Ministry of Science, ICT & Future Planning, Republic of Korea. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors declare that no competing interests exist. was significantly decreased in the CKmodified plan, as compared to that in the VMAT and CKoriginal plans, by 1.75- and 1.61-fold, respectively. Conclusions The tumor tracking capability of the CK system can significantly decrease the volume of normal liver tissue receiving > 15 Gy, while maintaining high precision in target localization, conformity, tumor coverage, and dose sparing of the OAR. Therefore, it can be a valuable SBRT option, particularly for HCC patients with poor liver function. Introduction Hepatocellular carcinoma (HCC) is one of the most common malignancies and the third most common cause of cancer-related deaths worldwide [ 1 ]. Surgery is the standard treatment for HCC, with 5-year survival rates of 50±70%; however, surgery is only suitable for < 30% of HCC patients at diagnosis [2±5]. Other modalities such as radiofrequency ablation or percutaneous ethanol injection have also been used as curative treatment options [ 6, 7 ]; however, these options are limited in cases where the HCC lesions are positioned at the top of the dome, at deep locations, and/or close to the main blood vessels (or bile duct). Therefore, non-invasive local therapeutic modalities such as radiotherapy (RT) are the choices of treatment in these clinical settings. Recent advances in RT technology not only enable highly focused dose delivery using intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT), but also facilitate precise tumor localization with image guidance during treatment. With these techniques, stereotactic body radiotherapy (SBRT) can deliver a highly focused ablative dose to the tumor, and accordingly achieve effective tumor control while minimizing the radiationinduced toxicity to normal tissue. Several studies have reported that an SBRT dose of 24±60 Gy administrated in 3±6 fractions is safe and efficacious for the treatment of HCC [8±12]. Considering the radiobiologically parallel architecture of liver tissue, preserving the `critical volume' of normal liver tissue is essential for preventing radiation-induced liver injury by SBRT [ 10, 13, 14 ]. Schefter et al. suggested 700 cc of the normal liv (...truncated)


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KyoungJun Yoon, Jungwon Kwak, Byungchul Cho, Jin-hong Park, Sang Min Yoon, Sang-wook Lee, Jong Hoon Kim. Gated Volumetric-Modulated Arc Therapy vs. Tumor-Tracking CyberKnife Radiotherapy as Stereotactic Body Radiotherapy for Hepatocellular Carcinoma: A Dosimetric Comparison Study Focused on the Impact of Respiratory Motion Managements, PLOS ONE, 2016, Volume 11, Issue 11, DOI: 10.1371/journal.pone.0166927