Gustavo Viani: Stereotactic Body Radiotherapy in Oligometastatic Breast Cancer – What Does the Evidence Show?

Gustavo Viani, Professor of Radiation Oncology at Ribeirão Preto Medical School, University of Sao Paulo, shared on LinkedIn:

“Stereotactic Body Radiotherapy (SBRT) in Oligometastatic Breast Cancer: What Does the Evidence Show?

Oligometastatic breast cancer (OMBC) represents an intermediate state between localized and widespread metastatic disease, characterized by limited metastases (typically ≤5). It’s a condition that opens the door to promising treatment strategies, such as SBRT.

Why is this important?
Metastases account for up to 90% of cancer-related deaths. By integrating SBRT with systemic therapies, we aim to control metastatic lesions and potentially improve survival outcomes. But what does the research say? Let’s dive into some key studies:
Study 1: SABR-COMET Trial

• Objective: Evaluate SBRT in patients with ≤5 metastases across various cancers.
• Results:
• Overall Survival (OS): 8-year survival: 27.2% (SBRT) vs. 13.6% (control) (HR = 0.50; CI: 0.30–0.84; p = 0.008).
• Takeaway: SBRT significantly improved long-term survival in a mixed cancer population.

Study 2: CURB Trial (Phase II)

• Objective: Compare standard care (SOC) vs. SOC + SBRT in OMBC or NSCLC after systemic therapy.
• Results:
• Progression-Free Survival (PFS): 7.2 months (SBRT) vs. 3.2 months (SOC) (HR = 0.53; p = 0.0035).
• OS: No significant improvement in OMBC.
• Takeaway: SBRT delayed progression but didn’t show OS benefits for breast cancer patients.

Study 3: NRG-BR002 Trial

• Objective: Assess SBRT’s impact in newly diagnosed OMBC patients.
• Results:
• OS: 3-year survival: 71.8% (SBRT) vs. 68.9% (SOC) (p = 0.54).
• PFS: No significant difference.
• Takeaway: SBRT didn’t improve OS or PFS, likely due to effective systemic therapies already in use.

Study 4: David et al. (Multicenter Study)

• Objective: Evaluate SBRT in patients with ≤5 metastases from various cancers.
• Results:
• PFS: Median of 5.2 months with SBRT.
• Toxicity: No grade ≥3 toxicities reported.
• Takeaway: SBRT is safe and offers modest control, but its role in OMBC is still evolving.

Key Takeaways:

• SBRT high PFS in many trials and OS in mixed cancer populations (e.g., SABR-COMET).
• Patient selection is critical: Benefits are clearer in patients with fewer metastases, better performance status, and tumors responsive to radiation.

Challenges and the Future of SBRT in OMBC:

• Results vary, underscoring the need for better patient stratification.
• Future trials should focus on combining SBRT with systemic therapies and refining criteria for optimal outcomes.

Conclusion:

SBRT is a promising tool in OMBC management, but not all patients benefit equally. Tailoring treatments to integrate local and systemic therapies is essential to achieve the best outcomes.

What are your thoughts?
Do you think SBRT should be more widely applied in OMBC, or should we wait for more data? ”

Gustavo Viani, MD is an Associate Professor in the Department of Medical Imaging, Hematology, and Oncology at Hospital das Clínicas, Faculty of Medicine of Ribeirão Preto, University of São Paulo (FMRP-USP). Dr. Viani’s research focuses on radiation oncology, with expertise in brachytherapy, stereotactic radiosurgery, dose fractionation, radiation tolerance, and overall oncology practices.