Role of stereotactic body radiotherapy (SBRT) for metastatic cancer patients beyond the traditional oligometastatic setting: a narrative review for an evolving concept

Background and Objective: The management of metastatic cancer is shifting from a strict division between curative local therapy and palliative systemic treatment toward a biology-driven continuum. In this setting, stereotactic body radiotherapy (SBRT), or stereotactic ablative radiotherapy (SABR), has emerged as an effective consolidative approach for patients with limited metastatic burden. Its role is now being explored beyond the classical oligometastatic paradigm, including oligoprogressive and selected polymetastatic disease. This narrative review summarizes the evidence supporting SBRT/SABR in patients with metastatic burden exceeding the traditional definition (≤3–5 metastases), focusing on emerging clinical scenarios.

Methods: A structured PubMed/MEDLINE search identified studies published between January 2000 and December 2025 using MeSH and free-text terms related to stereotactic radiotherapy and metastatic disease states. Randomized trials, prospective cohorts, and retrospective studies evaluating SBRT/SABR in oligoprogressive and other non-classical settings were included. Reviews, case reports, and preclinical studies were excluded. Due to heterogeneity in definitions and study designs, findings were synthesized narratively.

Key Content and Findings: Prospective and observational data show that SBRT/SABR achieves high local control with acceptable toxicity in oligometastatic disease and is increasingly investigated in patients with higher metastatic burden. The conventional cutoff of ≤3–5 metastases appears arbitrary, with ongoing trials assessing broader indications. Clinical benefit is strongly influenced by tumor biology, with more favorable outcomes in prostate and renal cell carcinoma than in other malignancies. SBRT/SABR is also used in oligoprogressive disease to prolong systemic therapy efficacy and for local symptom control. Patient-reported outcomes suggest disease progression, rather than treatment toxicity, is the main driver of quality-of-life decline.

Conclusions: SBRT/SABR may extend beyond the oligometastatic paradigm, but lesion count alone is insufficient for patient selection. Optimal use requires individualized, biology-driven strategies. Future research should refine selection criteria, incorporate biomarkers, and clarify integration with systemic therapies.