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

Table 5 Conformity and Intermediate dose spillage for singular and synchronously treated lesions

All patients	No Radiation Pneumonitis (n = 85)	Symptomatic Radiation Pneumonitis (n = 8)	P value
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%)
Singular lesions	No Radiation Pneumonitis (n = 77)	Symptomatic Radiation Pneumonitis (n = 6)	P value
Conformity Index (RxV / PTV)
Median	1.05	0.99	0.01
Range	0.89–1.44	0.98–1.03	0.01
Intermediate Dose Spillage^a (R50V /PTV)
No deviation (%)	32 (41.6%)	2 (40.0%)	1.00^†
Minor deviation (%)	42 (54.5%)	3 (60.0%)
Major deviation (%)	3 (3.9%)	0 (0.0%)
Synchronously treated lesions	No Radiation Pneumonitis (n = 8)	Symptomatic Radiation Pneumonitis (n = 2)	P value
Conformity Index (RxV / PTV)
Median	1.07	1.06	NR
Range	0.96–1.17	1.04–1.09	NR
Intermediate Dose Spillage (R50V /PTV)
No deviation (%)	4 (50.0%)	0 (0.0%)	0.56
Minor deviation (%)	3 (37.5%)	2 (100.0%)
Major deviation (%)	1 (12.5%)	0 (0.0%)

Abbreviations: RxV Volume receiving prescription dose, PTV Planned Target Volume, R50V Volume receiving 50% of the prescription dose. NR Not reportable given small patient number size. Symptomatic Radiation Pneumonitis = RTOG G3+ or CTCAE G2–3+ 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

ISSN: 1748-717X