Comparative Outcomes of Central and Ultracentral Lung Tumors Managed With Five-Fraction Stereotactic Body Radiation Therapy

Central (CLT) and ultracentral (UCLT) lung tumors can be at higher risk for treatment related mortality following stereotactic body radiation therapy (SBRT) and the preferred dose and fractionation is unclear. We assessed the toxicity and outcomes of patients with CLT and UCLT who underwent definitive five-fraction SBRT.We reviewed the charts of patients with either CLT or UCLT managed with SBRT from June 2010-April 2019. CLT were defined as gross tumor volume within 2 cm of either the proximal bronchial tree, trachea, mediastinum, aorta, or spinal cord. UCLT were defined as GTV abutting any of these structures. Toxicity was graded by the Common Terminology Criteria for Adverse Events version 5.0. Propensity score matching was performed for gender, performance status, and history of prior lung cancer. Survival outcomes evaluated by Cox regression and Kaplan-Meier estimation.Within this cohort of 83 patients, the median age was 73.1 years with a median follow up of 29.9 months. All patients underwent 5 fraction SBRT, with dose range of 50-60 Gy. Most patients had T1 tumors (68.7%) and 43 (51.8%) were considered UCLT. In 20 (50%) patients with CLT, the proximal bronchial tree was the closest central structure while the aorta was the closest structure in 16 (37.2%) of UCLT patients. Grade 2+ toxicity was similar between the two groups, 11 (27.5%) for CLT and 13 (30.2%) (P = 0.78) for UCLT patients. Furthermore, there was no difference in grade 3 toxicity with 3 (7.5%) CLT and 4 (9.3%) UCLT patients (P = 0.77) and no observed grade 4+ events. There was no difference in crude local failure (5% vs 7.0%) (P = 0.34) or recurrence rates (22.5% vs 9.3) (P = 0.09). Multivariate analysis adjusting for gender, performance status, prior lung cancer, history of diabetes, history of heart disease, and prescription volume revealed UCLT to be associated with worse overall survival (OS) (P = 0.02) but not freedom from progression (FFP). Using propensity score match pairing, 29 match pairs were generated finding UCLT to correlate with reduced non-cancer related survival (NC-OS) and OS, but not FFP.Definitive 5 fraction SBRT yielded similar toxicity profiles for CLT and UCLT. Despite no difference in FFP, UCLT were associated with worse (NC-OS) and OS.