CT ventilation image-guided helical Tomotherapy at sparing functional lungs for locally advanced lung cancer: analysis of dose-function metrics and the impact on pulmonary toxicity

Table 2 Summary of ROI-based lung DVH metrics, functional map-based DFH metrics and DFH metrics-based Normal tissue complication probabilities (NTCP) for grade 2 + radiation pneumonitis (RP) among RP-risk benefit patients (Group 1)

Variable	Planning strategy
Variable	Anatomical plan	Func_ plan _Top10	Func_ plan _Top20	Func_ plan _Top30	Func_ plan _Top40	Func_ plan _Top50
DFH metric-based NTCP model (toxicity probability of the mean)
NTCP_fV10(%)	38.37 ± 17.14	44.63 ± 21.83	40.84 ± 22.01	33.82 ± 17.35	30.98 ± 15.76^*	29.77 ± 15.46^**
Ventilation map-based lung DFH metrics (mean values)
fV5 (%)	63.94 ± 16.45	68.19 ± 16.29	64.21 ± 15.86	57.66 ± 15.70^*	54.70 ± 18.36^*	52.97 ± 17.18^**
fV10(%)	44.69 ± 13.77	49.77 ± 17.22	46.45 ± 18.00	40.26 ± 15.74	37.77 ± 15.40^*	36.86 ± 14.96^*
fV20 (%)	26.41 ± 12.48	24.84 ± 12.24	25.21 ± 12.41	24.05 ± 11.70^*	23.20 ± 11.55^*	23.06 ± 11.57^*
fMLD (Gy)	8.12 ± 2.96	8.17 ± 2.91	8.06 ± 3.04	7.64 ± 3.04^*	7.55 ± 3.23^*	7.44 ± 3.20^*
Structure-based lung DVH metrics (mean values)
V5 (%)	62.32 ± 12.34	66.09 ± 12.53	63.11 ± 11.60	57.76 ± 11.02^*	55.15 ± 12.94^**	53.51 ± 11.85^**
V10(%)	43.24 ± 9.77	49.87 ± 12.88	47.60 ± 12.94	41.45 ± 11.04	38.62 ± 10.82	37.38 ± 10.36^*
V20 (%)	24.47 ± 8.92	24.00 ± 9.41	24.92 ± 9.63	23.70 ± 9.05	22.88 ± 8.78	22.52 ± 8.69
MLD (Gy)	13.13 ± 3.16	13.47 ± 3.21	13.46 ± 3.42	13.18 ± 3.37	11.97 ± 4.26	12.40 ± 3.63

^*p < 0.05 and **p < 0.01, indicate significantly decreased when compared with anatomical plan; Func_plan _{Top10/20/30/40/50}, means top 10%/20%/30%/40%/50% percentile functional volume were defined as the high-functional lung in planning optimization

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