Assessment of an experimental re-irradiation model

2019 Fiscal Year Final Research Report

• Project/Area Number: 17K16493
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Radiation science
• Research Institution: Kindai University
• Principal Investigator: DOI Hiroshi 近畿大学, 医学部, 講師 (50529047)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 再照射 / 強度変調放射線治療 / 定位放射線治療 / 動物実験モデル / 放射線治療 / 放射線照射 / マウスモデル / 低酸素

Outline of Final Research Achievements

We aimed to elucidate the pathological findings following acute and late re-irradiation in a preclinical model. Mice were divided into five treatment groups: sham-irradiation (Sham-IR), 10-12 Gy (Single IR Acute), 15 Gy (Single IR Late), 15 Gy followed by 10-12 Gy re-irradiation 7 days later (Re-IR Acute), or 15 Gy followed by 10-12 Gy re-irradiation 12 weeks later (Re-IR Late). Mice were sacrificed after either single irradiation or re-irradiation for pathological assessment. The Re-IR Late group had significantly lower numbers of crypts with apoptotic cells than those observed in mice in the Single IR Acute group. There were no significant differences between the Single IR Acute and re-IR Acute groups in cell proliferation or in a crypt survival assay. Re-irradiation with a long interval after the first irradiation may cause similar acute biological effects in normal intestine as observed following irradiation without re-irradiation.

Free Research Field

放射線腫瘍学

Academic Significance and Societal Importance of the Research Achievements

近年の放射線治療技術により、腫瘍に限局した放射線治療が可能となり、照射野内再発に対する再照射が試みられている。再照射後の有害事象が臨床研究から報告されているものの、組織学的に解析した報告は臨床・基礎実験ともに乏しい。本研究では、前臨床試験で使用可能な再照射の動物実験モデルを確立できた。長期経過観察後の腹部への再照射における急性期反応は細胞死、放射線障害後の細胞増殖能ともに初回照射と同等であることを示した。一方で待機期間が短い場合には障害が増強されることが明らかになった。これらの知見は将来の臨床研究の礎にすることができ、意義深い。