Dose-response relationship for radiation-induced pneumonitis after pulmonary stereotactic body radiotherapy.
OBJECTIVE
To evaluate dosimetric factors predictive for radiation-induced pneumonitis (RP) after pulmonary stereotactic body radiotherapy (SBRT).


METHODS
A retrospective analysis was performed based on 59 consecutive patients treated with cone-beam CT-based image-guided SBRT for primary NSCLC (n=21) or pulmonary metastases (n=54). The majority of patients were treated with radiosurgery of 26 Gy to 80% (n=29) or three fractions of 12.5 Gy to 65% (n=40). To correct for different single fraction doses, local doses were converted to 2 Gy equivalent normalized total doses (NTDs) using α/β ratio of 3 Gy for RP. Dose-volume parameters and incidences of RP ≥ grade II SWOG were fitted using NTCP models.


RESULTS
Eleven patients developed RP grade II. With an average MLD of 10.3±5.6 Gy to the ipsilateral lung, a significant dose-response relationship was observed: the MLD was 12.5±4.3 Gy and 9.9±5.8 Gy for patients with and without development of RP, respectively. Additionally, volumes of the lung exposed to minimum doses between 2.5 and 50 Gy (V(2.5)-V(50)) were correlated with incidences of RP with a continuous decrease of the goodness of fit for higher doses.


CONCLUSIONS
The MLD and V(2.5)-V(50) of the ipsilateral lung were correlated with incidences of RP after pulmonary SBRT.
Guckenberger
Matthias
M
Department of Radiation Oncology, University of Würzburg, Würzburg, Germany. guckenberger_m@klinik.uni-wuerzburg.de
Baier
Kurt
K
Polat
Buelent
B
Richter
Anne
A
Krieger
Thomas
T
Wilbert
Juergen
J
Mueller
Gerd
G
Flentje
Michael
M
D000230:Adenocarcinoma / Q000532:radiotherapy*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002294:Carcinoma, Squamous Cell / Q000532:radiotherapy*; D016009:Chi-Square Distribution; D054893:Cone-Beam Computed Tomography; D019583:Dose Fractionation, Radiation; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000532:radiotherapy* / Q000556:secondary; D008297:Male; D008875:Middle Aged; D009010:Monte Carlo Method; D017564:Radiation Pneumonitis / Q000209:etiology*; D015641:Radiography, Interventional; D016634:Radiosurgery / Q000009:adverse effects*; D011879:Radiotherapy Dosage; D012189:Retrospective Studies; D012307:Risk Factors; D018709:Statistics, Nonparametric