SBRT Alone Yields Significant STFS, Manageable Toxicity in Oligometastatic Cancer

Metastasis-directed stereotactic body radiotherapy (SBRT) administered alone was associated with meaningful systemic therapy-free survival (STFS), with particular benefit in patients with oligometastatic prostate or renal cell cancer, according to a systematic review (CRD42024580877) published in JAMA Network.

Across 13 studies that provided 1- or 2-year STFS data for meta-analysis, the pooled 1- or 2-year STFS rate was 69.7% (95% CI, 57.4%-80.8%). Considerable heterogeneity was also observed (I² = 93.0%; P <.001). Among patients with renal cell cancer, the STFS rate was 87.0% (95% CI, 76.2%-95.2%; I² = 0%; P = .43); among those with prostate cancer, it was 78.1% (95% CI, 67.4%-87.3%; I² = 72.2%; P = .003). Across other disease states, the pooled STFS rate was 66.3% (95% CI, 58.8%-73.2%) in gynecological cancer and 56.2% (95% CI, 29.9%-80.2%) in sarcoma. The STFS rate was 47.1% (95% CI, 17.5%-77.8%) in studies with different tumor types (I² = 97.5%; P <.001).

Additionally, as reported in 7 studies mostly focused on prostate cancer, prostate-specific antigen (PSA) levels, favorable response after SBRT, and shorter doubling time for PSA levels were all factors associated with longer STFS.

Significantly, meta-regression indicated that histology was responsible for 35.7% of between-study heterogeneity (R² = 35.7%), with prominent levels of residual heterogeneity remaining (I² = 86.9%; P <.001). It was added that while histology did meaningfully contribute to the model overall (test of moderators: Q₄ = 9.52; P = .049), no individual subtype differed significantly from the reference category.

No publication bias was suggested. Via the Newcastle-Ottawa Scale, the risk of bias assessment demonstrated that 12 studies were high quality, 16 were moderate quality, and 1 was low quality.

A sensitivity analysis restricted to prospective studies performed to assess the consistency of findings found pooled 1- or 2-year STFS rates of 87.0% (95% CI, 76.2%-95.2%) and 71.1% (95% CI, 55.6%-84.5%) for renal cell cancer and prostate cancer, respectively. Heterogeneity was not important for renal cell cancer but was for prostate cancer. There was a low risk for publication bias with the sensitivity analysis.

“In this systemic review and meta-analysis, metastasis-directed SBRT without up-front systemic therapy was associated with clinically meaningful deferral of systemic treatment in patients with oligometastatic prostate and renal cell cancer,” wrote lead study author Jonas Willmann, MD, from the Department of Radiation Oncology at University Hospital Zurich, University of Zurich, in Zurich, Switzerland. “This strategy was associated with a low incidence of severe adverse events, potentially preserving QOL.”

This systematic review and meta-analysis included 29 studies with 2074 unique patients. Studies were identified through a literature search performed in PubMed and EMBASE on July 10, 2024. Included studies were published after January 2009 and investigated metastasis-directed SBRT of oligometastatic cancer, defined as 5 or fewer metastases, irrespective of primary tumor histology, without receipt of immediate systemic therapy. To be eligible for inclusion, studies had to be prospective or retrospective with at least 10 patients reporting STFS, progression-free survival, or overall survival. Only studies that reported 1- or 2-year STFS were included.

Data were extracted for study and patient characteristics, post-progression treatment decisions, treatment outcomes, and the proportion of patients without metastases at last follow-up.

Further, across 20 studies that reported adverse events, SBRT alone was well tolerated. The incidence of grade 3 or higher adverse effects ranged from 1.9% to 8.8% among studies that observed severe adverse events; 15 of 19 studies did not have rates of grade 3 or higher adverse effects available. Among the 6 studies that assessed quality of life (QOL), SBRT alone was associated with preserved QOL across disease sites.

Repeat SBRT was used to treat disease progression in 14 studies. Across prostate cancer studies, repeat SBRT was reported in 16% to 42% of patients. In patients with renal cell cancer, 44% received a second course of SBRT, and in patients with sarcoma, 25% underwent additional SBRT.

Freedom from metastases was observed in between 23% to 76% of patients with prostate cancer; in those with soft tissue sarcoma and bladder cancer, the rates were 6% and 23%, respectively. Across other cancer types, 38% of patients remained free from metastasis.

“Randomized clinical trials are needed to confirm outcomes and refine treatment strategies. Prognostic and predictive biomarkers should be explored to guide patient selection,” the authors concluded.

References

Willmann J, von Wachter C, Zehnder R, et al. Stereotactic body radiotherapy without systemic therapy for oligometastatic cancer: A systematic review and meta-analysis. JAMA Netw Open. 2025;8(12):e2549685. Published December 29, 2025. doi:10.1001/jamanetworkopen.2025.49685