Stereotactic body radiation therapy for spinal metastases: A new standard of care

Abstract

Advancements in systemic therapies for patients with metastatic cancer have improved overall survival and, hence, the number of patients living with spinal metastases. As a result, the need for more versatile and personalized treatments for spinal metastases to optimize long-term pain and local control has become increasingly important. Stereotactic body radiation therapy (SBRT) has been developed to meet this need by providing precise and conformal delivery of ablative high-dose-per-fraction radiation in few fractions while minimizing risk of toxicity. Additionally, advances in minimally invasive surgical techniques have also greatly improved care for patients with epidural disease and/or unstable spines, which may then be combined with SBRT for durable local control. In this review, we highlight the indications and controversies of SBRT along with new surgical techniques for the treatment of spinal metastases.

Keywords: SBRT; dose selection; local control; spinal metastases; target delineation.

Figure 1.

Patient with oligometastatic esophageal cancer presenting with a T11 metastasis and Bilsky 1A and lytic disease involving the vertebral body and ipsilateral pedicle with a pathologic fracture. The patient had mechanical and radicular pain and a Spinal Instability Neoplastic Score of 12. They also had radicular pain. The patient underwent T10–T12 instrumentation with a T11 left-sided transpedicular decompression and resection of tumor. The patient’s mechanical pain and radicular pain resolved after surgery and they underwent simulation 5 days later for postoperative stereotactic body radiation therapy with 28 Gy in 2 fractions.

Figure 2.

Patient with metastatic epithelioid sarcoma to T12 who underwent separation surgery with T10-L2 fusion using carbon fiber-reinforced polyetheretherketone instrumentation. Postoperative MRI and CT show minimal artifact for SRS planning.

Figure 3.

Patient with a sclerotic bone metastases involving the vertebral body and right lamina. The gross tumor volume (GTV) is contoured in red, the cord in yellow and the 1.5 mm cord planning target volume (PTV) in green. In accordance with contouring guidelines, the entire vertebral body and ipsilateral lamina, transverse process and pedicle are included as clinical target volume (CTV; blue). The spinous process was not included as that can be optional when lamina is not involved.

Figure 4.

Representative T1 unenhanced MRI slice demonstrating sacrum SBRT contours according to recent consensus guidelines. The gross tumor volume (red) involves segments 1, 2, 7, and 8 of the S1 vertebral body and the clinical target volume (green) includes segments 1, 2, 3, 6, 7, and 8. The thecal sac (purple) and bilateral nerve roots (orange and blue) are also contoured.