Stereotactic body radiotherapy: a new paradigm in the management of spinal metastases

Abstract

Spine stereotactic body radiotherapy is based on delivering high biologically effective doses to spinal metastases, with the intent to maximize both tumor and pain control. The purpose of this review is to outline the technical details of spine stereotactic body radiotherapy, contrast clinical outcomes to low biologically effective dose conventional palliative radiotherapy, discuss the role of surgery in the era of spine stereotactic body radiotherapy, and summarize the major serious adverse events that patients would otherwise not be at risk of with conventional radiotherapy.

Conflict of interest statement

Financial & competing interests disclosure

A Sahgal has received an honorarium from Medtronic's Kyphoplasty division for past educational seminars. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

No writing assistance was utilized in the production of this manuscript.

Figures

Figure 1.. A conventional radiotherapy treatment plan.

Illustrates the typical practice of including at least one vertebral body above and below the target volume (in red colorwash), and using an anterior and posterior parallel opposed beam arrangement. The target and normal tissues are exposed to the radiation. The patient was treated with 20 Gy in five fractions.

Figure 2.. Stereotactic body radiotherapy treatment and response.

(A) T2-weighted axial MRI illustrating C3 metastases in a patient with breast cancer, and a tumor involving the posterior elements and not the vertebral body. (B) The treatment plan isodose distribution of the patient who received 24 Gy in two fractions. (C) Axial T2-weighted MRI illustrating the response 2 months later, in which a drastic shrinkage in tumor size can be observed. This patient also had a complete response to pain.

Figure 3.. Elekta Synergy® unit curently in use at the University of Toronto and BodyFIX® system for immobilization.

(A) Elekta Synergy® (Elekta AB, Stockholm, Sweden), which is the linear accelerator-based system currently in use at the University of Toronto (ON, USA) [17]. (B) A patient fully immobilized in the BodyFIX® system (Elekta AB).

Figure 4.. Dose profile through a cross-section of the target volume.

(A) Axial computed tomography slice with the isodoses overlaid for a 24 Gy single-fraction plan. The planning target volume contour is shown in green with the spinal cord shown in red colorwash. The planning organ-at-risk volume for the cord is shown in yellow (represents a margin of 1.5 mm beyond the contoured spinal cord) and is typically restricted to a maximum point dose of 12.4 Gy. (B) The dose profile and dose gradient along the dashed white line in (A) is shown. The location of the cord and the cord planning organ-at-risk volume lateral edges are indicated on (B) by the vertical solid and dashed black lines, respectively.