Pulmonary injury and tumor response after stereotactic body radiotherapy (SBRT): Results of a serial follow-up CT study

Purpose: To evaluate the CT morphological pattern of tumor response and pulmonary injury after stereotactic body radiotherapy (SBRT) for early stage non-small lung cancer (NSCLC) and pulmonary metastases. Materials and methods: Seventy patients (lesions n = 86) with pulmonary metastases (n = 48) or primary early stage NSCLC (n = 38) were analyzed. Patients were treated with hypofractionated SBRT (three to eight fractions with a single dose between 6 and 12.5 Gy; n = 56) or with radiosurgery (26 Gy; n = 30). The pattern and sequence of pulmonary injury and of tumor response was evaluated in 346 follow-up CT studies, 4.9 on average. Results: Symptomatic pneumonitis was observed in 10% after a median interval of 5 months. No pulmonary reaction was observed in most patients 6 weeks after treatment; spotted-streaky condensations were characteristic between 3 months and 6 months. Dense consolidation and retraction started after 9 months and the fibrotic remodelling process continued for years. Ten targets relapsed after a median of 7 months. At 12 months complete response was seen in 43% and the differentiation of residual tumor from pulmonary reaction was not possible in 33%. Conclusions: A typical sequence of pulmonary reactions was observed without differences between hypofractionated treatment and radiosurgery. Onset of pneumonitis was later compared to conventionally fractionated radiotherapy. (c) 2007 Elsevier Ireland Ltd. All rights reserved.