Introduction: Ultra-central (UC) tumors, which are generally defined as tumors directly abutting the proximal bronchial tree, are difficult to treat with stereotactic body radiotherapy (SBRT) owing to possible serious complications. This systemic review and meta-analysis analyzed the early experiences and evaluated the efficacy and feasibility of SBRT for UC tumors.
Methods and materials: The present study adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Systemic searches of the EMBASE, PubMed, MEDLINE, and Cochrane library electronic databases were performed. The primary endpoints were two-year local control (LC), overall survival (OS), and grade ≥3 complication rates. A random-effects model was used to determine the pooled rates of the primary endpoints. Grade 5 complications were descriptively assessed.
Results: Nine studies involving 291 patients with UC tumors who underwent SBRT were included. The pooled two-year LC, two-year OS, and grade ≥3 complication rates were 96.7% (95% confidence interval [CI]: 91.0-98.9), 57.7% (95% CI: 32.0-79.8), and 23.2% (95% CI: 11.8-40.5), respectively. The incidence of grade 5 complication was 0-22% and was 0% in three of eight available studies. Hemorrhage (68.2%) was the commonest fatal complication. The risk factors for fatal hemoptysis included anticoagulant use, excessive maximum irradiation dose, endobronchial involvement, squamous histology, and bevacizumab exposure.
Conclusions: SBRT for UC tumors confers efficient LC, although the risk of complications was not negligible. Control of possible risk factors of hemorrhage and dose optimization through further studies are warranted.
Keywords: Stereotactic body radiotherapy; central tumor; feasibility; lung cancer; ultra-central tumor.