Dosimetric predictors of radiation-induced lung injury in stereotactic body radiation therapy

Figures & data

Table I.  Patients and tumours characteristics

Gender
Male	50 (83.3%)
Female	10 (17.7%)
Age
Median (range)	71.7 (53-85)
Primary NSCLC Histology
Squamous Cell Carcinoma	5 (12.1%)
Adenocarcinoma	8 (19.5%)
Anaplastic Large Cell Carcinoma	3 (7.5%)
NOS	8 (19.5%)
Bronchiolo-alveolar Cracinoma	1 (2.4%)
Unknown	16 (39%)
Metastases Histology
Lung	11 (58%)
Colo-rectal	3 (15.5%)
Pancreas	1 (5.3%)
Breast	1 (5.3%)
Kidney	1 (5.3%)
Liver	1 (5.3%)
Head&Neck	1 (5.3%)
Central Location	35 (55.6%)
Peripheral Location	28 (44.4%)
Upper Lobe	39 (61.9%)
Median Lobe	4 (6.3%)
Lower Lobe	20 (31.8%)

Table II.  RTOG lung toxicity scoring system

RTOG scoring system for ACUTE toxicity
0	1	2	3	4
No change	Mild symptoms of dry cough or dyspnea on exertion	Persistent cough requiring narcotic, antitussive agents/ dyspnea with minimal effort but not at rest	Severe cough unresponsive to narcotic antitussive agent or dyspnea at rest/ clinical evidence of acute pneumonitis/ intermittent oxygen or steroids may be required	Severe respiratory insufficiency/ continuous oxygen or assisted ventilation
RTOG scoring system for LATE toxicity
0	1	2	3	4
None	Asymptomatic or mild symptoms (dry cough)	Moderate symptomatic fibrosis or pneumonitis (severe cough) Low grade fever	Severe symptomatic fibrosis or pneumonitis	Severe respiratory insufficiency/ Continuous O2/ Assisted ventilation

Table III.  MLD₂ and NTCP mean values according to RTOG lung toxicity score

	Grade 0-1	Grade 2-3
MLD2	11.2 Gy (95% CI 10.1-12.3 Gy)	20.3 Gy (95% CI 16.6-23.9 Gy)
NTCP	4% (95% CI 2-5.9%)	37% (95% CI 11.6-62.3%)

Table IV.  Logistic regression analysis (correlation with RTOG grade 2-3 pulmonary toxicity)

	Odds Ratio	Std. Err.	z	p	95% Confidence Interval
MLD2	1.52	0.24	2.66	0.008	1.12	2.08
Primary/ Metastatic	3.03	3.98	0.84	0.399	0.23	39.79
Central/Peripheral	0.54	0.70	-0.48	0.634	0.04	6.75
Superior/Median/Inferior Lobe	1.53	0.89	0.73	0.464	0.49	4.79
PTV	1.03	0.03	1.05	0.293	0.98	1.08

Figure 1.  MLD2, NTCP and observed lung toxicity for ipsilateral lung. The histogram shows the percentage of RTOG grade 2–3 toxicity (the values in the bars indicate the number of patients with grade 2–3 toxicity over the total number of patients at risk within the same MLD range), while the dotted line the binary logistic fitting of observed data; the continuous line represents the gaussian fit between NTCP and MLD2.