Stereotactic Ablative Body Radiotherapy for Bone Only Oligometastatic Breast Cancer

“Practice Update” recently highlighted the results of a clinical trial involving stereotactic ablative body radiotherapy (SABR), a noninvasive approach for the treatment of oligometastases.

The results are published in The Breast , Volume 49, Pages 55-62 (February 2020). Read the full article here: DOI: 10.1016/j.breast.2019.10.016 https://www.thebreastonline.com/article/S0960-9776(19)30590-9/fulltext

OBJECTIVES

To determine the safety and feasibility of single fraction SABR for patients with bone only oligometastatic breast cancer. Secondary endpoints were local and distant progression-free survival (LPFS and DPFS), toxicity and response assessment.

METHODS AND MATERIALS

In this single institution prospective trial we screened patients with computed tomography, bone scan, and sodium fluoride positron emission tomography. Eligible patients had one to three bone only oligometastases. All patients were treated at a dose of 20Gy in 1 fraction to each metastasis. Kaplan-Meier methods were used to determine local and distant progression free survival (LPFS and DPFS). Toxicity was graded using Common Terminology Criteria for Adverse Event version 4.0.

RESULTS

15 eligible patients were recruited to the study. Median follow-up time was 24 months. The treatment was feasible in 12 (80%) of patients with 3 (20%) of patients having treatment delayed by more than 3 days. 10 (67%) of patients experienced grade 1 treatment related toxicity, 4 (27%) experienced grade 2 toxicity and no patients experienced grade 3 or 4 treatment related toxicity. The two-year LPFS was 100%, DPFS was 67%.

CONCLUSION

We observed that SABR is feasible, well tolerated and effective in this cohort with two thirds of patients disease-free at two years. In selected patients with bone-only oligometastatic disease, SABR could be considered a treatment option. Randomised trials are required to assess the impact of SABR on overall survival when compared to the standard of care.

TAKE-HOME MESSAGE

“Practice Update” offered the following summary from Neil Majithia, MD :
This prospective trial was designed to evaluate the use of single-fraction stereotactic ablative body radiotherapy (SABR) for 15 patients with bone-only oligometastatic breast cancer. The 2-year local progression-free survival rate was 100%; the 2-year distant progression–free survival rate was 67%.
SABR appears to be feasible and effective in this population. Randomized trials are warranted to compare outcomes with SABR and the current standard of care.

Read more oligometastatic research here:

Dr. Steven Chmura is leading a national team of radiation oncologists in a national Phase II/III open trial that randomizes breast cancer patients with only 1-2 metastases, called oligometastatic breast cancer, to compare survival outcomes in standard of care therapy with or without stereotactic body radiotherapy (SBRT) and/or surgical ablation.