Long-term clinical experience of high-dose ablative lung radiotherapy: High pre-treatment [18F]Fluorodeoxyglucose-positron emission tomography maximal standardized uptake value of the primary tumor adversely affects treatment outcome

Purpose: The aim of this study was to report the long-term clinical experience with lung stereotactic ablative radiotherapy (SABR). Methods: Between April 2004 and December 2011, 58 of 92 consecutive lung SABR cases were treated with a curative purpose and were eligible for inclusion. Forty patients were treated for primary lung cancer, and eighteen were treated for locally confined recurrent tumors. The majority of the cases were medically inoperable (65.5%). A median five fractions with a total dose of 30-60. Gy were prescribed to the planned target volume. We routinely performed an image-guided respiratory gating technique or four-dimensional computed tomography to minimize set-up errors and accurately determine target volumes. Results: The median follow-up was 23.8 (range, 1.5-77.2) months. The median age of the entire cohort was 73 (range, 48-90) years. The median gross tumor volume and maximal tumor diameter were 20 (range, 0.5-189.7) ml and 2.2 (range, 0.7-5.9) cm, respectively. The two-year local control (LC) rate was 92.1%, and the major pattern of failure was distant metastasis (25.9%). A high pre-treatment maximal standardized uptake value (mSUV) of the primary tumor significantly and adversely affected LC, local relapse-free survival, distant metastasis-free survival, cause-specific survival and overall survival. The toxicity rates (≥grade 2) were 34.5% and 35% for the central and peripheral tumors, respectively, and one grade 5 toxic event (death due to massive hemoptysis) occurred in a centrally located tumor at 16.7 months post-SABR. Conclusions: Lung SABR remains an effective and safe local treatment modality. Pre-treatment mSUV may be a helpful parameter to select patients requiring higher radiation doses and adjuvant systemic therapy for lung SABR.