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Table 3 Univariate analysis of associations between dosimetric factors and grade ≥ 3 RP (n = 67)

From: The risk and predictors for severe radiation pneumonitis in lung cancer patients treated with thoracic reirradiation

Variable Grade 0–2 (n = 49) Grade ≥ 3 (n = 18) P value
Initial-V5    0.047
  ≥ 53.15% 22 (44.9%) 13 (72.2%)  
  < 53.15% 27 (55.1%) 5 (27.8%)  
Initial-V20    0.152
  ≥ 18.04% 23 (46.9%) 12 (66.7%)  
  < 18.04% 26 (53.1%) 6 (33.3%)  
Initial-V50    0.633
  ≥ 2.04% 24 (49.0%) 10 (55.6%)  
  < 2.04% 25 (51.0%) 8 (44.4%)  
Initial-MLD    0.002
  ≥ 10.87 20 (40.8%) 15 (83.3%)  
  < 10.87 29 (59.2%) 3 (16.7%)  
Re-V5    0.001
  ≥ 32.7% 19 (38.8%) 15 (83.3%)  
  < 32.7% 30 (61.1%) 3 (16.9%)  
Re-V20    0.114
  ≥ 9.94% 22 (44.9%) 12 (66.7%)  
  < 9.94% 27 (55.1%) 6 (33.3%)  
Re-V50    0.532
  ≥ 1.25% 26 (53.1%) 8 (44.4%)  
  < 1.25% 23 (46.9%) 10 (55.6%)  
Re-MLD    0.001
  ≥ 6.63 19 (38.8%) 15 (83.3%)  
  < 6.63 30 (61.2%) 13 (16.7%)  
Composite-V5    < 0.001
  ≥ 68.13% 18 (36.7%) 16 (88.9%)  
  < 68.13% 31 (63.3%) 2 (11.1%)  
Composite-V20    0.033
  ≥ 28.04% 21 (42.9%) 13 (72.2%)  
  < 28.04% 28 (57.1%) 5 (27.8%)  
Composite-V50    0.304
  ≥ 7.23% 23 (46.9%) 11 (61.1%)  
  < 7.23% 26 (53.1%) 7 (38.9%)  
Composite-MLD    0.114
  ≥ 17.31 22 (44.9%) 12 (66.7%)  
  < 17.31 27 (55.1%) 6 (33.3%)  
Overlap-V5/Re-V5    0.035
 0–0.4 12 (24.5%) 2 (11.1%) 1.000*
 0.4–0.8 10 (20.4%) 10 (55.6%) 0.014*
 0.8–1 27 (55.1%) 6 (33.3%)  
  1. Abbreviations: RP radiation pneumonitis, Initial initial radiation plan, MLD mean lung dose, Re reirradiation plan, Composite composite plan, Overlap-V5/Re-V5 the overlap between V5 of initial RT and V5 of re-RT plans/V5 of re-RT plans, Vx percent volume of lung exposed to at least x Gy, * compared with overlap-V5/Re-V5 of 0.8–1