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.

Radiofrequency ablation (RFA) and ablative external beam radiotherapy (ablative RT) are commonly used to treat small intrahepatic malignancies. We meta-analysed oncologic outcomes and systematically reviewed the clinical consideration of tumour location and size. PubMed, Medline, Embase, and Cochrane Library databases were searched on February 24, 2022. Studies comparing RFA and ablative RT, providing one of the endpoints (local control or survival), and encompassing ≥5 patients in each arm were included. Twenty-one studies involving 4,638 patients were included. Regarding survival, the odds ratio (OR) was 1.204 (p = 0.194, favouring RFA, not statistically significant) among all studies, 1.253 (p = 0.153) among hepatocellular carcinoma (HCC) studies, and 1.002 (p = 0.996) among colorectal cancer metastasis studies. Regarding local control, the OR was 0.458 (p <0.001, favouring ablative RT) among all studies, 0.452 (p <0.001) among HCC studies, favouring the ablative RT arm, and 0.649 (p = 0.484) among colorectal cancer metastasis studies. Pooled 1- and 2-year survival rates for HCC studies were 91.8% and 77.7% after RFA, and 89.0% and 76.0% after ablative RT, respectively; and for metastasis studies were 88.2% and 66.4% after RFA and 82.7% and 60.6% after RT, respectively. Literature analysis suggests that ablative RT can be more effective than RFA for tumours larger than 2–3 cm or for specific sublocations in the liver (e.g. subphrenic or perivascular sites), with moderate quality of evidence (reference to the grading system of the American Society for Radiation Oncology Primary Liver Cancer Clinical Guidelines). The pooled grade ≥3 complication rates were 2.9% and 2.8% in the RFA and ablative RT arms, respectively (p = 0.952). Our study shows that ablative RT can yield oncologic outcomes similar to RFA, and suggests that it can be more effective for the treatment of tumours in locations where RFA is difficult to perform or for large-sized tumours. This study was registered with PROSPERO (Protocol No: CRD42022332997). Radiofrequency ablation (RFA) and ablative radiotherapy (RT) are non-surgical modalities for the treatment of small intrahepatic malignancies. Ablative RT showed oncologic outcomes at least similar to those of RFA, and was more effective at specific locations (e.g. perivascular or subphrenic locations).