Stereotactic ablative radiotherapy (SABR) for central lung tumors: Plan quality and long-term clinical outcomes

Background and purpose Central lung SABR is less established due to toxicity concerns. We describe plan quality and clinical outcomes for patients treated with VMAT SABR using 8 × 7.5 Gy. Materials and methods We studied 80 consecutive patients with primary NSCLC and PTV ≤2 cm from the proximal bronchial tree (PBT), treated between 2008 and 2013. Dosimetric data were compared with institutional guidelines and study protocols, and long-term clinical outcomes were analyzed. Results PTV V_95% was 60 Gy in 96% of patients. Dmax was ≥60 Gy in 40% of patients for PBT, 26.3% for aorta, 55% for heart, and 1.3% for trachea. Esophageal maximum Dmax was 58 Gy. Mean lung V_5Gy/V_20Gy was 21/8%. 54 patients (68%) exceeded RTOG0813 Dmax for ≥1 organ-at-risk (OAR), with 27 exceeding PBT Dmax. 5 of 78 patients (6.4%) with adequate follow-up information had grade 3 toxicity. Grade 4 toxicity was not observed. Treatment-related death was considered possible (n = 3) or likely (n = 3) in 6 patients (7.5%). With median follow-up of 47 months, 3-year survival was 53%, compared with 57% for 252 peripheral tumors treated with 3/5-fractions SABR in the same period (p = 0.369). Conclusions Although a substantial proportion of central SABR patients received ≥60 Gy to OARs, the 3-year survival was no different from peripheral SABR.