TOPLINE: 

Stereotactic body radiotherapy (SBRT) alone achieves a 69.7% pooled 1- or 2-year systemic therapy-free survival rate across cancer types, with the highest rates seen in renal cell and prostate cancers. The strategy shows a favorable safety profile, with most studies reporting no grade 3 or higher adverse events.

METHODOLOGY: 

• Oligometastatic disease represents a state of limited metastatic spread that may be amenable to targeted local therapies such as metastasis-directed SBRT. The potential for SBRT to delay or defer systemic therapy has not been comprehensively analyzed across different types of oligometastatic cancers.
• Researchers conducted a systematic review and meta-analysis of studies published between 2010 and July 2024 in which patients with oligometastatic disease (five or fewer metastases) received SBRT and no upfront systemic therapy. They identified 29 unique studies for the systematic review, of which 13 contributed data to the meta-analysis.
• Eight studies were prospective, including three randomized clinical trials. Prostate cancer was the most frequently studied cancer type (n = 14), followed by renal cell cancer (n = 2) and head and neck cancers (n = 2).
• The primary outcome of the meta-analysis was the pooled systemic therapy-free survival rate at 1 or 2 years.

TAKEAWAY: 

• The pooled 1- or 2-year systemic therapy-free survival rate across all cancer types was 69.7% (95% CI, 57.4%-80.9%). Renal cell cancer had the highest rate, at 87% (95% CI, 76.2%-95.2%), followed by prostate cancer at 78.1% (95% CI, 67.4%-87.3%). Based on a single study, 1-year systemic therapy-fee survival was 66.3% for patients with gynecologic cancers.
• Among 19 studies reporting on grade 3 or higher adverse events, 15 (79%) reported none. Of studies in which severe adverse events occurred, the proportion of affected patients ranged from 1.9% to 8.8%.
• Six studies assessed quality of life and found that SBRT alone was associated with preserved quality of life regardless of cancer type.
• Seven studies reported on the proportion of patients who remained free from metastases at last follow-up. For prostate cancer, those rates ranged from 23% (median follow-up, 68 months) to 76% (median follow-up, 30 months). Across all studies, 14%-44% of patients received repeat SBRT to manage limited progressive disease.

IN PRACTICE: 

“Our findings suggest that SBRT alone might be associated with substantial systemic therapy-free survival, particularly in prostate and renal cell cancers, with a favorable safety profile,” the study authors wrote. “Randomized clinical trials are needed to confirm outcomes and refine treatment strategies,” they concluded.

SOURCE: 

The study, led by Jonas Willmann, MD, of University Hospital Zurich in Zurich, Switzerland, was published online in JAMA Network Open.

LIMITATIONS: 

Most studies were retrospective, and considerable heterogeneity was observed across patient populations, treatment protocols, and criteria for defining oligometastatic disease. Although systemic therapy-free survival was highest for patients with renal cell cancer, no clinical trials have compared SBRT against observation in those patients.

DISCLOSURES:

The authors reported various financial relationships outside of the submitted work. A full list of disclosures is available in the original article.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.