RT Journal Article SR Electronic T1 Relationship Between Radiation Pneumonitis Following Definitive Radiotherapy for Non-small Cell Lung Cancer and Isodose Line JF In Vivo JO In Vivo FD International Institute of Anticancer Research SP 3441 OP 3448 DO 10.21873/invivo.12644 VO 35 IS 6 A1 SHIGENOBU WATANABE A1 ICHIRO OGINO A1 DAISUKE SHIGENAGA A1 MASAHARU HATA YR 2021 UL http://iv.iiarjournals.org/content/35/6/3441.abstract AB Background/Aim: It is important to identify radiation pneumonitis above Common Terminology Criteria for Adverse Events Grade 2 (G2) in order to safely continue durvalumab maintenance after chemoradiotherapy for advanced lung cancer. The aim of this study was to discover factors that predict pneumonitis above G2. Patients and Methods: A follow-up computed tomography (CT) image was superimposed on the planning CT image using deformable image registration (DIR). The pneumonitis area was contoured on follow-up CT after DIR and the dose-volume histogram parameters of the contoured pneumonitis area were calculated. Results: V5 (Percentage of total volume receiving ≥5 Gy) to V50 of pneumonitis were significantly lower in patients with G2 pneumonitis than in those with G1 pneumonitis. The pneumonitis V15 was the most significant. The group with pneumonitis V15 <87.10% had significantly more G2 pneumonitis than the group with pneumonitis V15 ≥87.10%. Conclusion: Pneumonitis V15 <87.10% was a risk factor for G2 pneumonitis.