Creating a model to predict the risk of bone damage after radiotherapy

2021 Fiscal Year Final Research Report

• Project/Area Number: 20K16401
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 50020:Tumor diagnostics and therapeutics-related
• Research Institution: National Institutes for Quantum Science and Technology
• Principal Investigator: Okonogi Noriyuki 国立研究開発法人量子科学技術研究開発機構, 量子医科学研究所 重粒子線治療研究部, 医長 (00750572)
• Project Period (FY): 2020-04-01 – 2022-03-31
• Keywords: 骨障害 / 不全骨折 / 放射線治療 / 重粒子線治療 / 有害事象 / DVH解析 / バイスタンダー効果

Outline of Final Research Achievements

The risk of pelvic bone damage after carbon-ion radiotherapy (C-ion RT) is still unclear. Hence, we assessed the risk of pelvic bone damage in uterine cancer patients who had received C-ion RT. The incidence of grade 1 or higher late bone damage (bone damage evident on only imaging modalities) was found in 22.3%, and the incidence of grade 2 or higher late bone damage (symptomatic bone damage) was found in 8.3% of patients. These incidences were similar to or slightly less than that of standard RT.
We further analyzed whether the quality of C-ion RT, i.e., linear energy transfer (LET), affected bone damage. We found that LET in C-ion RT was not associated with bone damage. Instead, patients over 50 years of age or current smokers had an increased fracture risk. We have also begun to analyze the effects of LET on bone cells. It seems that the bystander effect is not affected by LET (further studies are ongoing).

Free Research Field

放射線医学

Academic Significance and Societal Importance of the Research Achievements

重粒子線治療後の骨盤骨の骨障害のリスク評価は、世界で初めての報告となった。研究結果について、放射線治療分野における一流誌に投稿し、受理・掲載された（Radiother Oncol. 2021;156:56-61. doi:10.1016/j.radonc.2020.11.030.）。2022年度から進行子宮頸部腺癌に対する重粒子線治療が公的医療保険の適用となった。重粒子線治療後の骨障害の低減に繋がる研究成果であり、患者の治療後の生活の質の向上に資する可能性がある。