We know that SBRT can improve outcomes for patients with oligometastatic cancer. We also recently saw that controlling all sites of disease with SBRT is important in achieving those outcomes. On the other end of the spectrum is the use of SBRT to a limited number of disease sites along with immunotherapy in polymetastatic disease to induce an abscopal response. CHEERS was a randomized phase 2 trial where 99 patients receiving immune checkpoint inhibition (ICI) for metastatic cancer were randomized to the addition of SBRT (8 Gy x 3) to up to 3 sites of disease. Most patients (75%) had >3 sites of disease and 68% had progressed on at least 1 prior line of therapy. Even though SBRT achieved 75% local control, it did not significantly improve median PFS, which was a disappointing 4.4 v 2.8 months. SBRT was not associated with worse toxicity. Here again, we see that SBRT is an effective means of controlling sites of metastatic disease, but it does not appear to induce an abscopal effect. The benefit of SBRT is mainly seen in patients where all sites of disease can be treated. | Spaas, JAMA Oncol 2023
