Stereotactic body radiation therapy (SBRT) is a technique that utilizes precisely targeted radiation to a tumor while minimizing radiation to adjacent normal tissue. This targeting allows treatment of small- or moderate-sized tumors in either a single or limited number of dose fractions. SBRT may have a role in treating selected patients with painful bone metastases.
SBRT may be particularly useful for treating the spine, where there is a significant concern about normal tissue toxicity . SBRT may have a particularly important role in patients with epidural spinal cord compression who have relatively radioresistant tumors (eg, melanoma, renal cell cancer) and those who require retreatment for previously irradiated spinal metastases or epidural spinal cord compression [14-18]. The precision in delivering RT in this manner may decrease the risk of toxicity to the spinal cord.
The role of this approach is illustrated by a large series, in which SBRT (12.5 to 25 Gy, median 20 Gy) was used to treat 393 patients (including 93 with renal cell and 38 with melanoma metastases), 69% of whom had received prior RT . Long-term pain improvement was experienced by 86% of all patients, including 94% of those with renal cell cancer and 96% of patients with melanoma. Long-term tumor control was achieved in 90% of lesions treated with SRS as a primary treatment modality, including 87% of patients with renal cell cancer and 75% of those with melanoma. Of the 32 patients with a progressive neurologic deficit prior to treatment, 27 (84%) improved clinically.
The use of SBRT to treat spinal metastases may be associated with an increased risk of vertebral compression fracture. In a series of 252 patients in which 410 spinal segments were treated with SBRT, 57 fractures (14%) were observed, 27 of which were new and 30 were progression of preexisting fractures . Multivariate analysis suggested that the risk was greatest in those treated with a single fraction of 20 Gy or greater and those with a baseline fracture, lytic tumor, or spinal deformity.