Metastasis-directed SBRT alone may be enough for patients with oligometastatic disease

Metastasis-directed stereotactic body radiotherapy (SBRT) alone can delay the need for systemic therapy in some patients with oligometastatic cancer, with low risks of treatment-related adverse events (TEAEs), according to a meta-analysis.

Pooled data from 29 unique studies involving 2,074 patients who received metastasis-directed SBRT and no upfront systemic therapy for oligometastatic cancer (≤5 metastases) showed that the systemic therapy–free survival (STFS) at 1 or 2 years was 69.7 percent (95 percent confidence interval [CI], 57.4–80.9) across cancer types. [JAMA Netw Open 2025;8:e2549685]

The highest STFS rates were observed in renal cell cancer (87 percent, 95 percent CI, 76.2–95.2) and prostate cancer (78.1 percent, 95 percent CI, 67.4–87.3). STFS rates were lower in other cancer types, including gynaecological cancer (66.3 percent, 95 percent CI, 58.8–73.2) and sarcoma (56.2 percent, 95 percent CI, 29.9–80.2).

SBRT without upfront systemic therapy was well tolerated and associated with preserved quality of life across disease sites. The frequency of grade ≥3 adverse effects ranged from 1.9 percent to 8.8 percent.

The proportion of patients remaining metastasis-free at last follow-up ranged from 23 percent (median follow-up 68 months) to 76 percent (median follow-up 30 months) for prostate cancer and was lower for soft tissue sarcoma (6 percent; median follow-up 36 months) and bladder cancer (23 percent; median follow-up 25 months). In one study that involved multiple cancer types, the proportion of patients remaining free from metastases was 38 percent (median follow-up 35 months).

Factors associated with longer STFS included lower PSA levels, favourable response after SBRT, and shorter doubling time for PSA levels. However, this finding was based on studies that mostly focused on prostate cancer and should therefore be considered hypothesis generating, according to the investigators.

“The ability of SBRT to defer systemic therapy has important clinical implications, particularly for patients with limited metastatic burden and favourable tumour biology. By postponing systemic therapy, patients may avoid or delay the associated toxic effects and preserve their quality of life,” they said.

Additionally, the investigators pointed out that SBRT is not just a one-and-done treatment and can be used repeatedly to manage disease progression while deferring systemic therapy. Across the studies included in the meta-analysis, repeat SBRT was delivered in 16 percent to 43 percent of prostate cancer patients, 44 percent of those with renal cell cancer, 25 percent of those with sarcoma, and between 18 percent and 34 percent of those with various primary tumours.

In terms of the safety of repeat SBRT, a dedicated retrospective study for oligometastatic disease showed low rates of adverse effects, even with multiple consecutive SBRT courses and in combination with systemic therapy. [Radiother Oncol 2023;184:109671] 

Overall, the present data suggest that SBRT alone may be an acceptable treatment strategy instead of immediate systemic therapy in selected patients with oligometastatic cancer, the investigators said. “In this vein, implementing predefined criteria for initiating systemic therapy is crucial to standardize treatment sequencing and optimize patient outcomes. These criteria were often undefined or left to physician discretion, underscoring the need for clear guidelines in clinical practice.”