Background There is currently no consensus on optimal management of patients with primary or recurrent non-resectable/residual retroperitoneal sarcomas (RPS). The objective of this study was to document the outcomes of patients with primary or recurrent non-resectable/residual RPS treated in our center with definitive radiotherapy (RT), and to perform systematic review on that topic. Methods A retrospective analysis of consecutive RPS patients treated in our center between 2000 and 2019 was performed. All consecutive patients who underwent definitive conformal RT with image guidance for primary or recurrent non-resectable or macroscopically residual RPS were included. Additionally, the systematic review compliant with the recommendations of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses was performed.Results 14 patients who met aforementioned criteria were found. Data on clinicopathological characteristics, RT and response to treatment were presented. RT allowed achieving prolonged local control of the disease i.e. no local progression of the disease for more than six months after RT in 12 patients. Achieved local control lasted more than 24 months in six cases, with none or minimal toxicity. 11 studies were included in the systematic review. Our results are in concordance to reports included in the review.Conclusions RT provided satisfactory local disease control with acceptable treatment tolerance in patients with primary or recurrent non-resectable/residual RPS. RT represents valuable treatment modality in this selected group of patients. Additional RT modalities i.e. particle therapy, MRI-guided RT or GRID/Lattice RT may be introduced to improve local control and minimize toxicity.