Stereotactic body radiotherapy for pulmonary metastases

Purpose

The aim of this retrospective study was to evaluate the feasibility, safety, and effectiveness of stereotactic body radiotherapy (SBRT) for pulmonary metastases.

Patients and methods

Between April 2007 and March 2011, 87 patients underwent SBRT for pulmonary metastases using the in-house Air-Bag System^TM to obtain the four-dimensional image for treatment planning and to reduce intrafractional intrathoracic organ motion with abdominal compression to reduce the risk of radiation pneumonitis. Survival and respiratory adverse events were analyzed.

Results

The 2- and 3-year overall survival (OS) rates were 47 and 32?%, and the corresponding cause-specific survivals were 52 and 36?%. The 2- and 3-year OS rates were 57 and 49?% for patients in group 1, respectively, while the corresponding OS rates were 48 and 21?%, and 40 and 32?% for patients in groups 2 and 3, respectively. The 2- and 3-year local control (LC) rates were 80 and 80?%, respectively. The corresponding intrathoracic progression-free survival rates were 40 and 32?%, respectively. Concerning adverse respiratory events after SBRT for pulmonary metastases, 14?% were grade 0 (G0), 66?% G1, 13?% G2, 6?% G3, and 1?% G4. Concerning the adverse respiratory events (NCI-CTC) by grade scale, 1- and 2-year cumulative probabilities of radiation pneumonitis were 12 and 20?% for G2 and 4 and 10?% for G3/4, respectively. The mean values for cumulative V20 were 11.6?±?8.5?%, 29.8?±?18.6?%, and 25.7?±?12.8?% in G0/1, G2, and G3/4, respectively. The number of pulmonary metastases that could be safely treated with SBRT was 6 PTVs (or seven gross tumor volumes) within a cumulative V20 of 30?% under the restricted intrafractional respiratory tumor motion using the Air-Bag System^TM.

Conclusion

We propose that the number of pulmonary metastases that can be safely treated with SBRT is 6 PTVs with a cumulative V20 of 30?% under the restricted respiratory tumor motion using the Air-Bag System^TM. SBRT for pulmonary metastases offers locally effective treatment for recurrent or residual lesions after first line chemotherapy.