The first National Institutes of Health (NIH) National Cancer Institute (NCI)-funded clinical study examining stereotactic body radiotherapy (SBRT) in the treatment of oligometastatic breast, prostate, and non-small cell lung (NSCLC) cancers displayed evidence that SBRT can be safely used to treat patients who have multiple metastases. These results were recently published in JAMA Oncology.

The results of the Phase I NRG-BR001 trial, conducted by the NCI National Clinical Trials Network group NRG Oncology, indicate that SBRT treatment in standard doses was safe for 35 evaluable patients with a median of three metastases. There were no dose-limiting toxicities and over 50% of trial participants were alive at two years following treatment.

“Prior to this trial, little to no evidence was available to support that SBRT is a safe and tolerable treatment option for patients who have multiple metastases. Researchers have hypothesized that SBRT could improve survival outcomes for this patient population; however, it was imperative we determine the safety of this procedure, appropriate dose and scheduling, and how to coordinate across multiple centers the quality assurance of the procedures prior to testing its efficacy,” says Steven J. Chmura, MD, PhD, of the Department of Radiation and Cellular Oncology at the University of Chicago Comprehensive Cancer Center and the lead author of the NRG-BR001 manuscript.

Chmura adds, “To ensure safety, this trial used an extensive radiation QA process to test the accuracy of treating moving tumors and was the first NRG trial to require the use of 3D image guidance during treatment for soft tissue tumors.”

NRG-BR001 enrolled up to six evaluable patients for each of the following seven selected anatomic locations: bone/osseous (BO), spinal/paraspinal (SP), peripheral lung (PL), central lung (CL), abdominal/pelvic (AP), mediastinal/cervical lymph node (MC), and liver (L). As a single patient could contribute to more than one location, the safety question was able to be answered with 35 evaluable patients from the 42 enrolled trial participants.

Patients were required to have three to four metastases or two metastases near each other. SBRT starting dose was 50 GY over five fractions for the CL and MC groups, 45 GY over three fractions for the PL, AP, and L groups and 30 Gy over three fractions for the BO and SP group. Additional patients would be accrued as needed at defined de-escalated doses if any of the starting doses were not deemed to be safe.

The 35 evaluable patients had breast (n=12), NSCLC (n=10), and prostate (n=13) cancers. No dose de-escalations were needed. There were eight instances of grade 3 adverse events. There were no treatment-related deaths. SBRT for multiple metastases is now utilized in multiple ongoing Phase II and III NCI-sponsored trials. Follow-up research should be done in long surviving oligometastatic patients.

“These are important data from the multicenter study, confirming that complicated stereotactic body radiotherapy to multiple sites is safe and feasible. We eagerly await the results of ongoing, larger randomized trials to demonstrate how effective this is when compared to drug therapy alone for metastatic cancer,” says Mitchell Machtay, MD, the associate dean for clinical cancer research at the Penn State College of Medicine and the interim group chair for NRG Oncology.