量研学術機関リポジトリ「QST-Repository」は、国立研究開発法人 量子科学技術研究開発機構に所属する職員等が生み出した学術成果（学会誌発表論文、学会発表、研究開発報告書、特許等）を集積しインターネット上で広く公開するサービスです。 Welcome to QST-Repository where we accumulates and discloses the academic research results(Journal Publications, Conference presentation, Research and Development Report, Patent, etc.) of the members of National Institutes for Quantum and Radiological Science and Technology.
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[Purpose] QST hospital treats patients using carbon-ion radiotherapy (CIRT) with head and neck cancer. For the head and neck cancer, normal tissues such as brain and optic nerve are close to the irradiation field such that those may receive radiation damage due to the CIRT. Although a dose-volume histogram (DVH) is conventionally used for the clinical analysis, we have developed a dose-averaged LET (LETd) calculation tool. We clinically analyzed head and neck cancer patients using this tool.
[Methods] We used the Heavy Ion Plan (HIPLAN) treatment planning system in the CIRT. The clinical analysis tool developed and implemented in the HIPLAN can calculate the LETd and its standard deviation. For this study, we will select head and neck cancer patients, who were treated by the CIRT from October 2006 to December 2013. Those patients had follow-up more than 3 years and did not receive other radiotherapy. In this study, the12 patients were clinically analyzed using the analysis tool for local control, brain injury, and optic neuropathy.
[Results] By implementing the clinical analysis tool in HIPLAN, it is possible to easily calculate and analyze LETd for each patient. The LETds for 12 patients were calculated, and analyzed for local control, brain injury, and optic neuropathy. Out of 12 patients, 2, 12 and 8 patients developed local recurrence, brain injury and optic neuropathy. In this study, there was no new finding for the relation between the LETd and those clinical parameters.
[Conclusion] We developed the LETd calculation tool. The12 patients with head and neck cancer were clinically analyzed using this system for local control, brain injury, and optic neuropathy. Although we could not confirm the usefulness of the LETd analysis because of the small number of patients, we will continue to analyze more patients in the future.
Clinical Analysis of Dose-averaged LET Calculation in Carbon-Ion Radiotherapy for Head and Neck Cancer
