Correlation of dosimetric factors with the development of symptomatic radiation pneumonitis in stereotactic body radiotherapy

Table 2 Volume, Conformity, Intermediate dose spillage and Mean Lung Dose characteristics

Characteristic	No Radiation Pneumonitis (n = 85)	Symptomatic Radiation Pneumonitis (n = 8)	P value
Gross Tumor Volume (GTV), cm³
Median	3.0	15.2	< 0.001
Range	0.3–24.3	3.4–41.7	< 0.001
Integrated Tumor Volume (ITV), cm³
Median	6.0	35.4	< 0.001
Range	0.8–39.9	9.0–151.8	< 0.001
Planning Tumor Volume (PTV), cm³
Median	24.9	77.9	< 0.001
Range	5.7–133.3	32.9–370.5	< 0.001
Prescription dose (RxV), cm³
Median	26.3	78.1	< 0.001
Range	6.2–135.1	34.3–361.9	< 0.001
ITV minus GTV, cm³
Median	3.2	10.2	0.002
Range	0–25.8	5.6–33.0	0.002
Conformity Index (RxV / PTV)
Median	1.05	1.00	0.04
Range	0.89–1.44	0.98–1.09	0.04
Intermediate Dose Spillage^a (R50V/PTV)
No deviation (%)	36 (42.4%)	2 (28.6%)	0.78^†
Minor deviation (%)	45 (52.9%)	5 (71.4%)
Major deviation (%)	4 (4.7%)	0 (0.0%)
Total Mean Lung Dose, Gy
Median	3.1	7.0	< 0.001^‡
Range	1.0–11.0	4.1–9.6	< 0.001^‡
Contralateral Mean Lung Dose, Gy
Median	1.1	2.0	0.001^‡
Range	0.2–3.6	1.6–6.4	0.001^‡
Ipsilateral Mean Lung Dose, Gy
Median	4.7	9.1	< 0.001^‡
Range	1.8–10.7	7.0–13.2	< 0.001^‡

RxV Volume receiving prescription dose, R50V Volume receiving 50% of the prescription dose. Symptomatic Radiation Pneumonitis = RTOG G3+ or CTCAE G2+ RP
^aOf the entire cohort, only one patient was not able to have Intermediate Dose Spillage calculated due to a large PTV size of 370 cm³. This patient developed symptomatic radiation pneumonitis
Bolded P-values indicate statistical significance
All P-values are from Wilcoxon Rank Sum test unless otherwise noted
^†P-value from Fischer exact test
^‡Bonferroni Adjusted P-value

ISSN: 1748-717X