Evaluation of lung injury after three-dimensional conformal stereotactic radiation therapy for solitary lung tumors: CT appearance.
OBJECTIVE
To evaluate the computed tomographic (CT) appearance of tumors and lung injury in patients who have undergone stereotactic radiation therapy (SRT) for solitary lung tumors.


METHODS
Twenty-seven patients with primary lung cancer and four with metastatic lung cancer who underwent SRT for solitary lung tumors were enrolled for evaluation. SRT was delivered by using a three-dimensional conformal technique with a stereotactic body frame. A total dose of 48 Gy was administered in four fractions during a period of 2 weeks. After SRT, follow-up CT images were obtained every 2-3 months. Radiation-induced pulmonary injuries were classified into four patterns on CT images. The minimal lung dose to areas demonstrating pulmonary injury at CT was evaluated, and the correlation between the dose and the percentage volume of the whole lung irradiated by more than 20 Gy in total (V20) was assessed by using Spearman rank correlation.


RESULTS
Tumor shrinkage continued for 2-15 months after SRT. Asymptomatic changes in the irradiated lung were noted at CT in all patients within 2-6 months (median, 4 months) after SRT. As the pattern at pulmonary CT changed, patchy consolidation was more predominantly seen as an acute change than were slight homogeneous increase in opacity, discrete consolidation, or solid consolidation; solid consolidation was the more predominantly seen late change. The minimal lung dose to the area demonstrating pulmonary injury in each patient ranged between 16 and 36 Gy (median, 24 Gy). The dose was significantly (P <.001) inversely correlated with the V20 in each patient.


CONCLUSIONS
The reaction to SRT of the lungs seems similar to the reaction to conventional radiation therapy.
Aoki
Tetsuya
T
Department of Therapeutic Radiology and Oncology, Graduate School of Medicine, Kyoto University, 54 Shogoin Kawahara-cho, Sakyo, Kyoto 606-8507, Japan.
Nagata
Yasushi
Y
Negoro
Yoshiharu
Y
Takayama
Kenji
K
Mizowaki
Takashi
T
Kokubo
Masaki
M
Oya
Natsuo
N
Mitsumori
Michihide
M
Hiraoka
Masahiro
M
D005500:Follow-Up Studies; D006801:Humans; D008171:Lung Diseases / Q000000981:diagnostic imaging* / Q000209:etiology*; D008175:Lung Neoplasms / Q000532:radiotherapy*; D020266:Radiotherapy, Conformal / Q000009:adverse effects* / Q000379:methods; D013997:Time Factors; D014057:Tomography, X-Ray Computed