Evaluation of predictivity or Stochastic Linear Quadratic model (LQ model) to calculate tumor control probability of radiotherapy

• Project/Area Number: 17K10464
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Radiation science
• Research Institution: Hokkaido University
• Principal Investigator: Onimaru Rikiya 北海道大学, 医学研究院, 客員研究員 (80374461)
• Project Period (FY): 2017-04-01 – 2021-03-31
• Project Status: Completed (Fiscal Year 2020)
• Budget Amount: ¥4,680,000 (Direct Cost: ¥3,600,000、Indirect Cost: ¥1,080,000); Fiscal Year 2019: ¥1,040,000 (Direct Cost: ¥800,000、Indirect Cost: ¥240,000); Fiscal Year 2018: ¥910,000 (Direct Cost: ¥700,000、Indirect Cost: ¥210,000); Fiscal Year 2017: ¥2,730,000 (Direct Cost: ¥2,100,000、Indirect Cost: ¥630,000)
• Keywords: LQ model / 確率 / 放射線治療 / 不均一線量分布 / 局所制御率 / シミュレーション / 乱数 / 放射線腫瘍学 / Linear Quadratic model / 確率分布 / 確率論 / LQモデル / 効果予測

Outline of Final Research Achievements

We developed random variable (RV) approach to calculate Tumor Control Probability (TCP) of inhomogeneous radiation dose distribution, using computer simulation to count surviving cells after radiotherapy using random variables.
Considering the variance of surviving probability, TCP is worse with increasing the variance of surviving probability. The effect is less when the surviving probability is changed in each irradiation. We also confirmed that RV approach is able to calculate TCP adequately if dose distribution of tumor is inhomogeneous.

Academic Significance and Societal Importance of the Research Achievements

近年の放射線治療では強度変調放射線治療や定位放射線治療が普及している。従来の放射線治療では腫瘍内部の線量の違いは大きくなく、ほぼ均一に照射されていた。近年普及した強度変調放射線治療や定位放射線治療では腫瘍内部の線量は従来の放射線治療と比較して差が大きく、従来の放射線治療の効果予測法とは異なる効果予測法の開発が望まれていた。
本研究では放射線治療中の細胞生存率を変化させたり、線量分布が不均一であったりといった状況でも放射線治療後の腫瘍制御率を計算する手法を開発した。

Research Products

• [Journal Article] Preliminary Study of Cell Survival Modelling Considering Stochastic Fluctuations in Cell Survival Rates During Radiation Therapy (2018)
  • Author(s): Onimaru R.、Mori T.、Yasuda K.、Shirato H.
  • Journal Title: International Journal of Radiation Oncology*Biology*Physics Volume: 102 Issue: 3 Pages: e338-e339
  • DOI: 10.1016/j.ijrobp.2018.07.1035
• [Presentation] 不均一線量分布（不均一照射後生存確率）における局所制御率算出の試み (2019)
  • Author(s): 鬼丸力也、安田耕一、森崇、白土博樹
  • Organizer: 第32回日本放射線腫瘍学会学術大会
• [Presentation] Preliminary Study of Cell Survival Modelling Considering Stochastic Fluctuations in Cell Survival Rates During Radiation Therapy (2018)
  • Author(s): Onimaru R, Mori T, Yasuda K, Shirato H.
  • Organizer: American Society for Radiation Oncology (ASTRO) 60th Annual meeting
  • Int'l Joint Research