A 62-year-old male patient presents with severe lower back pain radiating to his right lower abdomen and right leg. He previously underwent a right nephrectomy for renal cell carcinoma. On physical exam, he has weakness with right knee extension which is affecting his ability to ambulate. An MRI is performed and is shown in Figures A and B. Staging studies determine this to be an isolated metastatic lesion. What is the next best step in this patient's treatment?