The Emerging Role of Extracranial Stereotactic Ablative Radiotherapy for Metastatic Renal Cell Carcinoma: A Systematic Review

Context: Although the management of metastatic renal cell carcinoma (mRCC) has been revolutionized by the advent of new systemic agents, still few patients experience a long-term durable response. Stereotactic ablative radiotherapy (SABR) is nowadays com-monly used as metastasis-directed therapy (MDT), but limited data exist on how best to implement this strategy as part of a multimodal approach.Objective: To evaluate the potential role of extracranial SABR in mRCC and to identify future therapeutic developments of SABR in different disease settings.Evidence acquisition: A systematic review was conducted in May 2022 according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) state-ment on the PubMed database. Thirty-four studies were selected for inclusion in this systematic review.Evidence synthesis: SABR has been used with four main goals: (1) eradication of the whole metastatic burden in synchronous and metachronous oligometastatic patients, resulting in a long-term local control (LC) rate of >90% and median progression-free sur-vival (PFS) ranging between 8 and 15 mo; (2) eradication of oligoprogressive lesions, enabling an extension of the duration of the systemic therapy by approximately 9 mo; (3) improvement of the response to systemic therapy in polymetastatic patients, result -ing in an overall response rate ranging from 17% to 56%; and (4) cytoreduction in poly-metastatic mRCC patients, with LC rates ranging between 71% and 100%, and preservation of the renal function, but unclear PFS and overall survival impact. Overall, the combination of SABR and systemic agents has been associated with overall good tolerance, with grade >= 3 toxicity ranging from 0% to 13%.

Automated summary

Stereotactic ablative radiotherapy (SABR) has potential in the management of metastatic renal cell carcinoma (mRCC) as a part of multimodal approaches. SABR can achieve complete remission of metastatic lesions, prolong the duration of systemic therapy, improve treatment response in polymetastatic patients, and reduce tumor burden in some cases. The impact on renal function is unclear. Overall, the combination of SABR and systemic agents is well-tolerated.