Ohashi, Toshio



School of Medicine, Department of Radiology (Radiation Oncology) (Shinanomachi)


Associate Professor

External Links

Profile Summary 【 Display / hide

  • 日本医学放射線学会専門医、がん治療認定医、日本医学放射線学会研修指導者

Career 【 Display / hide

  • 1998.05


  • 2000.05


  • 2002.01


  • 2004.02


  • 2006.12


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Academic Background 【 Display / hide

  • 1998.03

    Keio University, Faculty of Medicine

    University, Graduated

Academic Degrees 【 Display / hide

  • 博士(医学), Keio University, Dissertation, 2009.02

Licenses and Qualifications 【 Display / hide

  • 日本医学放射線学会専門医, 2005.08

  • がん治療認定医, 2008.04

  • 日本医学放射線学会研修指導者, 2012.12


Research Areas 【 Display / hide

  • Radiation science (Radiation Science)


Books 【 Display / hide

  • 最先端医療機器の病院への普及展望と今後の製品開発

    大橋俊夫,大出健一,深田恭平,花田剛士, 技術情報協会, 2018.05

    Scope: 105-112

  • 密封小線源治療 診療・物理QAマニュアル

    大橋 俊夫, 金原出版, 2013.10

    Scope: 115-123

  • 放射線治療グリーンマニュアル

    OHASHI TOSHIO, ANDO YUTAKA, 金原出版, 2005.03

    Scope: 123-163

  • 放射線治療グリーンマニュアル


    Scope: 51-55

  • 放射線治療 専門医にきく最新の臨床

    茂松 直之、大橋 俊夫, 中外医学社, 2004.07

    Scope: 98-100

Papers 【 Display / hide

  • Comparison of prostate verification with implanted gold markers in tissue surrounding the prostate and pelvic bony anatomy for external beam radiation therapy following low-dose-rate brachytherapy: a prospective clinical trial

    Kaneda T, Ohashi T, Hanada T, Takenaka K, Nishimura S, Sakayori M, Sutani S, Momma T, Shigematsu N

    Journal of Radiation Research (Oxford University Press)  61 ( 5 ) 784 - 790 2020.09

    Research paper (scientific journal), Joint Work, Accepted,  ISSN  04493060

     View Summary

    © The Author(s) 2020. We aimed to investigate whether gold marker implantation in the tissue surrounding the prostate could accurately monitor setup errors during external beamradiation therapy (EBRT) following low-dose-rate (LDR) brachytherapy. Thirty-eight patients had confirmed intermediate- or high-risk prostate cancer and received EBRT following LDR brachytherapy. In>175 computed tomography imaging sessions, the average values of the weekly setup error during EBRT to the prostate centroid at the time of gold marker matching in the surrounding tissue of the prostate and pelvic bonematching were measured and then compared using theWilcoxon signed-rank test.Goldmarkermatching in the surrounding tissue of the prostate estimated setup errors better than those estimated by bone matching (3D displacement=2.7±2.0 vs 3.8±2.6 mm, P<0.01).Overall, the standard deviation of systematic (Σ) and random (σ) setup error was lower with goldmarkermatching than with bonematching (3D displacement=1.8 and 1.1mm vs 2.1 and 1.6 mm, respectively). With gold marker matching, the setup error of the position of the prostate centroid was smaller, and the optimal setup margin was lower than that with bone matching (2Σ + 0.7σ and 2.5_ + 0.7σ of 3D displacement = 4.3 and 5.2 mm vs 5.3 and 6.4 mm, respectively). This high-precision radiotherapy approach placing gold markers in the surrounding tissue of the prostate can allow more accurate setup during EBRT following LDR brachytherapy.

  • ”RapidPlan”の臨床活用 ~経験を活かし共有する~

    大橋 俊夫、深田恭平、池島健吾

    INNERVISION (金原出版)  34 ( 11 ) 90 - 91 2019.11

    Research paper (scientific journal), Joint Work, Except for reviews

  • Genitourinary toxicity after permanent iodine-125 seed implantation: The nationwide Japanese prostate cancer outcome study of permanent iodine-125 seed implantation (J-POPS)

    Tanaka N., Yorozu A., Kikuchi T., Higashide S., Kojima S., Ohashi T., Katayama N., Nakamura K., Saito S., Dokiya T., Fukushima M.

    Brachytherapy (Brachytherapy)  18 ( 4 ) 484 - 492 2019.07

    Research paper (scientific journal), Joint Work, Accepted,  ISSN  15384721

     View Summary

    © 2019 American Brachytherapy Society Purpose: The purpose of this study was to evaluate acute and late genitourinary (GU) toxicity and to elucidate factors associated with GU toxicity in patients with prostate cancer treated with permanent seed implantation (PI) enrolled in a nationwide prospective cohort study in Japan. Methods and Materials: Of 2,354 patients enrolled in this study, GU toxicity was evaluated in 2,339 patients at 3, 12, 24, and 36 months after PI. To elucidate independent factors predictive of acute and late Common Terminology Criteria for Adverse Events Grade 2 or higher (Grade ≥2) GU toxicity, multivariate logistic regression analyses were carried out. Regarding acute urinary retention (AUR), the incidence rate and the recovery rate for AUR were estimated using the Kaplan–Meier curve. Results: Approximately 53% of the patients treated with PI alone and 42% of those treated with combination therapy with PI therapy and external beam radiation therapy showed urinary frequency/urgency at 3 months. The multivariate analysis revealed that age, prostate volume, pretreatment international prostate symptom score, drinking status, and PI were independent predictors of acute GU toxicity Grade ≥2. Of all patients, 53 (2.3%) suffered from AUR, and 49 (92.5%) recovered from AUR with a median time of 4.3 months during the followup period. Conclusions: The results of GU toxicity in Japanese patients who underwent low-dose-rate brachytherapy were acceptable and comparable to those previously reported in U.S. patients. The patients treated with PI alone showed a significantly higher incidence rate of GU toxicity than did those undergoing combination therapy with PI and external beam radiation therapy in the acute phase.

  • Nationwide Japanese Prostate Cancer Outcome Study of Permanent Iodine-125 Seed Implantation (J-POPS): first analysis on survival

    Ito K, Saito S, Yorozu A, Kojima S, Kikuchi T, Higashide S, Aoki M, Koga H, Satoh T, Ohashi T, Nakamura K, Katayama N, Tanaka N, Nakano M, Shigematsu N, Dokiya T, Fukushima M; J-POPS Investigators

    Int J Clin Oncol (International Journal of Clinical Oncology)  23 ( 6 ) 1148 - 1159 2018.12

    Research paper (scientific journal), Joint Work, Accepted,  ISSN  13419625

     View Summary

    Investigating oncological outcomes in patients registered in the Japanese Prostate Cancer Outcome Study of Permanent Iodine-125 Seed Implantation (J-POPS) in terms of biochemical relapse-free survival (bRFS) by the Phoenix and the newly developed J-POPS definitions, exploration of predictive factors for bRFS, and preliminary verification of pitfalls of prostate-specific antigen (PSA) failure definitions.

    Between July 2005 and June 2007, 2316 clinically localized patients underwent permanent seed implantation. The primary endpoint was bRFS. One of the secondary endpoints was overall survival (OS).

    The median age was 69 and performance status was 0 in 99.1% of participants. The median biologically effective dose (BED) was about 180 Gy2. During a median follow-up of 60.0 months, 8.4 and 5.9% had PSA failure by the Phoenix and the J-POPS definitions, respectively. The 5-year bRFSs based on the Phoenix and the J-POPS definitions were 89.1 and 91.6%, respectively. The 5-year OS was 97.3%. According to multivariate analyses, only age affected bRFS based on the Phoenix definition, whereas the risk group and BED independently affected bRFS based on the J-POPS definition. A spontaneous PSA decrease was seen in 91.1% of participants after PSA failure based on the Phoenix definition alone, but in only 22.2% after PSA failure based on the J-POPS definition alone.

    The world's largest registration study, J-POPS, consisted of patients with longevity, and a highly quality-controlled BED resulted in excellent bRFS and OS. The high likelihood of PSA bounce by the Phoenix definition should be taken into account, especially in younger patients.

  • Plan reproducibility of intraoperatively custom-built linked seeds compared to loose seeds for prostate brachytherapy

    Kaneda T, Ohashi T, Sakayori M, Sutani S, Yamashita S, Momma T, Takahashi S, Hanada T, Shigematsu N

    J Contemp Brachytherapy (Journal of Contemporary Brachytherapy)  10 ( 4 ) 291 - 296 2018.10

    Research paper (scientific journal), Joint Work, Accepted,  ISSN  1689832X

     View Summary

    © 2018 American Public Health Association Inc. All Rights Reserved. Purpose: Few studies have compared the implant quality of linked and loose seeds for prostate brachytherapy. This study aimed to evaluate and compare plan reproducibility of intraoperatively built custom linked seeds and loose seeds for prostate brachytherapy. Material and methods: Between December 2010 and March 2014, 76 localized prostate cancer patients received Iodine-125 brachytherapy with external beam radiotherapy. Linked and loose seeds were implanted in 39 and 37 patients, respectively. The primary endpoint was the mean (± standard deviation) of the absolute change in the minimum dose received by 90% of the prostate volume between intraoperative and post-operative planning (ΔD 90 ) to confirm plan reproducibility. Comparisons between the groups were evaluated using 2-sample t tests. Results: The ΔD 90 values were 6.95 ± 11.6% and -0.41 ± 8.5% for the loose and linked seed groups, respectively (p < 0.01). The linked seed group showed decreased post-operative D 90 (118.8% vs. 127.2%), V 150 (51.7% vs. 66.7%), and RV 100 (0.44 ml vs. 0.61 ml) compared to the loose seed group (p < 0.01), whereas lung migration tended to be reduced (0% vs. 8%). Conclusions: The plan reproducibility of the linked seed group was better than that of the loose seed group. Moreover, the linked seed group showed less migration and lower rectal dose.

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Papers, etc., Registered in KOARA 【 Display / hide

Presentations 【 Display / hide

  • ハイドロゲルスペーサーが前立腺I-125小線源療法の線量パラメータに与える影響


    第32回日本放射線腫瘍学会学術大会 (名古屋) , 2019.11, Poster (general)

  • 正常組織有害事象発生率の推定したパラメータ及び患者データ群に関する頑健性


    第32回日本放射線腫瘍学会学術大会 (名古屋) , 2019.11, Poster (general)

  • 乳房照射におけるTPS上の表面線量分布と皮膚表面の色調変化について


    第32回日本放射線腫瘍学会学術大会 (名古屋) , 2019.11, Poster (general)

  • 前立腺癌シード治療においてスペーサー注入前プランで直腸線量評価は省略可能か?


    第32回日本放射線腫瘍学会学術大会 (名古屋) , 2019.11, Poster (general)

  • 機械学習を用いた前立腺癌シード治療後直腸出血予測モデル構築の試み


    第32回日本放射線腫瘍学会学術大会 (名古屋) , 2019.11, Oral Presentation(general)

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Research Projects of Competitive Funds, etc. 【 Display / hide

  • 前立腺癌の放射線治療における尿路有害事象予測モデルの構築


    Grant-in-Aid for Scientific Research, Research grant, Principal Investigator

  • シード線源を用いた化学小線源療法の開発


    Grant-in-Aid for Scientific Research, Research grant

  • 前立腺癌小線源治療における尿道線量リアルタイムモニタリングと有害事象の予測


    Grant-in-Aid for Scientific Research, Research grant

  • 融合画像作成による高精度前立腺癌小線源治療法の確立


    Grant-in-Aid for Scientific Research, Research grant

  • 頭頚部腫瘍放射線治療時の口腔内急性および慢性障害を防止するための装具の開発


    Grant-in-Aid for Scientific Research, Research grant

Awards 【 Display / hide

  • Good Poster Award (The 7th Japan-Taiwan Radiation Oncology Symposium)

    Takenaka K, Ohashi T, Nishimura S, Sakayori M, Kaneda T, Momma T, Shigematsu N, 2019.05, The 7th Japan-Taiwan Radiation Oncology Symposium

    Type of Award: Awards of International Conference, Council and Symposium

  • Outstanding Contribution in Reviewing

    OHASHI TOSHIO, 2017.02, Brachytherapy

    Type of Award: Celebration by Official journal of a scientific society or Academic Journal

  • 日本医学放射線学会電子ポスター(CyPos)賞(Bronze Medal)

    白石悠,深田淳一,茂松直之,北川雄光,大橋俊夫,沓木章二,久保敦司, 2008.04, 食道癌に対する化学放射線 / 放射線治療後の胸水、心嚢液貯留

    Type of Award: Awards of National Conference, Council and Symposium

  • 日本放射線腫瘍学会ポスター発表学会賞(金賞)

    金田和也,宮澤雷太,深田淳一,茂松直之,大橋俊夫,菅原章友,国枝悦夫,奥洋平,中島淳,久保敦司, 2007.12, 前立腺シード小線源治療におけるTRUS-CT融合画像を用いた恥骨弓干渉の予測

    Type of Award: Awards of National Conference, Council and Symposium

  • 第6回日本癌治療学会研究奨励賞

    OHASHI TOSHIO, 2006.10, Acute urinary morbidity following I-125 prostate branchytherapy

    Type of Award: Awards of National Conference, Council and Symposium


Courses Taught 【 Display / hide





Courses Previously Taught 【 Display / hide

  • 臨床実習担当「放射線治療計画実習」

    Keio University, 2015, Full academic year, Major subject, Laboratory work/practical work/exercise, Within own faculty

  • 放射線科系統講義「小線源治療」

    Keio University, 2015, Full academic year, Major subject, Lecture, Within own faculty

  • 臨床実習担当「放射線治療計画実習」

    Keio University, 2014, Full academic year, Major subject, Laboratory work/practical work/exercise, Within own faculty

  • 放射線科系統講義「小線源治療」

    Keio University, 2014, Full academic year, Major subject, Lecture, Within own faculty

  • 臨床実習担当「放射線治療計画実習」

    Keio University, 2013, Full academic year, Major subject, Laboratory work/practical work/exercise, Within own faculty

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Educational Activities and Special Notes 【 Display / hide

  • 第20回共用試験医学系OSCE認定評価者講習会


    , Special Affairs

  • 第15回慶應義塾大学病院臨床研修指導医養成ワークショップ


    , Special Affairs


Memberships in Academic Societies 【 Display / hide

  • 第10回前立腺癌密封小線源永久挿入治療研究会, 

  • 第15回 ヨウ素125シード線源永久挿入による前立腺癌密封小線源療法技術講習会, 

  • 日本放射線腫瘍学会小線源治療部会第14回研究会, 

  • 泌尿器腫瘍放射線研究会(GUTR), 

  • 日本放射線腫瘍学会小線源治療部会ガイドライン改訂作業委員会, 


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Committee Experiences 【 Display / hide

  • 2018.10

    座長, 第31回日本放射線腫瘍学会学術大会

  • 2018.06

    座長, 日本放射線腫瘍学会小線源治療部会第20回研究会

  • 2018.04

    座長, 第77回日本医学放射線学会総会・学術集会

  • 2016.04

    代議員, 日本医学放射線学会

  • 2016.01

    座長, 第11回J-POPS中間報告会

     View Remarks


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