SBRT safe in patients with prostate cancer and multiple metastases

Stereotactic body radiotherapy (SBRT) is a safe treatment for patients with prostate cancer and multiple metastases, according to findings from the National Cancer Institute (NCI)-funded phase 1 NRG-BR001 trial published in JAMA Oncology.^1,2

The NRG-BR001 trial, which also included patients with breast and lung cancer who had multiple metastases, showed that there were no dose-limiting toxicities (DLTs) with SBRT across all 3 tumor types. Patients in the trial had oligometastatic disease with 3 to 4 metastases or 2 metastases close together (≤5 cm).

“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,” lead study author Steven J. Chmura, MD, PhD, of the Department of Radiation and Cellular Oncology at the University of Chicago Comprehensive Cancer Center, stated in a press release.

“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,” added Chmura.

Between August 4, 2014, and March 20, 2018, the study enrolled 42 patients, 35 of whom were eventually evaluable for DLTs. Of these 35 patients, 13 (37.1%) had prostate cancer, 12 (34.3%) had breast cancer, and 10 (28.6%) had NSCLC. The mean age was 63.1 years, 57.1% were men, and 85.7% were White.

The median number of metastases treated for each patient was 3. Patients had metastases to 7 locations in the body: bone/osseous, spinal/paraspinal, peripheral lung, central lung, abdominal-pelvic, mediastinal/cervical lymph node, and liver.

No protocol-defined DLTs were observed. There were 8 cases of grade 3 adverse events (AEs) likely related to study treatment. These occurred in 7 patients between around 125 and 556 days after starting SBRT. “Late grade 3 AEs demonstrate the need for extended follow-up in long-surviving patients with oligometastatic disease,” the authors wrote in their conclusion.

Multiple ongoing phase 2/3 NCI-supported randomized trials, including NRG-BR002 and NRG-LU002, are further examining SBRT in patients with cancer and multiple metastases.

“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,” Mitchell Machtay, MD, associate dean for Clinical Cancer Research at the Penn State College of Medicine and the interim Group Chair for NRG Oncology, stated in the press release.

Reference

1. NRG Oncology Study Shows Safety of Using Stereotactic Body Radiotherapy to Treat Multiple Metastases. Published online April 27, 2021. Accessed April 27, 2021. https://bit.ly/3nCiuat.

2. Chmura S, Winter KA, Robinson C, et al. Evaluation of safety of stereotactic body radiotherapy for the treatment of patients with multiple metastases: findings from the NRG-BR001 phase 1 trial [published online ahead of print April 22, 2021]. JAMA Oncol. doi: 10.1001/jamaoncol.2021.0687