Local response and pathologic fractures following stereotactic body radiotherapy versus three-dimensional conformal radiotherapy for spinal metastases - a randomized controlled trial

Abstract

BackgroundThis was a prespecified secondary analysis of a randomized trial, which analyzed bone density following stereotactic body radiotherapy (SBRT) versus conventional three-dimensional conformal radiotherapy (3DCRT) as part of palliative management of painful spinal metastases.MethodsFifty-five patients were enrolled in this single-institutional randomized exploratory trial (NCT02358720). Participants were randomly assigned to receive SBRT (single-fraction 24 Gy) or 3DCRT (30 Gy/10 fractions). Quantitative bone density was evaluated at baseline, 3 and 6 months in both irradiated and unirradiated spinal bodies, along with rates of pathologic fractures and vertebral compression fractures.ResultsAs compared to baseline, bone density became significantly higher at 3 and 6 months following SBRT by a median of 33.8% and 72.1%, respectively (p < 0.01 for both). These figures in the 3DCRT cohort were 32.9% and 41.2%, respectively (p < 0.01 for both). There were no statistical differences in bone density between SBRT and 3DCRT at 3 (p = 0.629) or 6 months (p = 0.327). Subgroup analysis of osteolytic metastases showed an increase in bone density relative to baseline in the SBRT (but not 3DCRT) arm. Bone density in unaffected vertebrae did not show substantial changes in either group. The 3-month incidence of new pathological fractures was 8.7% in the SBRT arm vs. 4.3% in the 3DCRT arm.ConclusionsDespite high ablative doses in the SBRT arm, the significant increase in bone density after 3 and 6 months was similar to that of 3DCRT. Our trial demonstrated a moderate rate of subsequent pathological fracture after SBRT. Future randomized investigations with larger sample sizes are recommended.Trial registrationwww.clinicaltrials.gov: NCT02358720 on 9nd of February 2015.

Stereotactic Body Radiotherapy (SBRT) for Oligometastatic Spine Metastases: An Overview

“…Sprave et al assessed bone mineral density as a prespecified secondary endpoint in their study comparing conventional palliative radiotherapy to spine SBRT (101). Both conventional radiotherapy and SBRT increased bone mineral density at 3- and 6-months with one technique not being statistically significantly better.…”

“…With two fractions, a point max dose of 12.5, 14.6, 15.7, 16.4, and 17.0 Gy yielded an estimated risk of 1, 2, 3, 4, and 5% of myelopathy, respectively. In the reirradiation setting, after conventional external beam radiotherapy, a cumulative thecal sac point maximum dose of 70 Gy in equivalent 2 Gy per fractions (utilizing an alpha-beta ratio of 2) was suggested as long as sufficient time had elapsed since initial treatment (≥5 months) and the point maximum for retreatment should not exceed 25 Gy in equivalent 2 Gy fractions (101).…”

Diagnostic Imaging Modalities to Assess Treatment Response of Bone Metastasis in Patients Receiving Palliative Radiotherapy: A Scoping Review of the Literature

“…The imaging modalities chosen to measure radiographical response included computed tomography (CT), [13][14][15][16][17][18][19][20][21][22] fluorodeoxyglucose-positron emission tomography, [22][23][24] diffusion-weighted magnetic resonance imaging (DW-MRI), 20,25,26 magnetic resonance imaging (MRI), 20 and X-ray (XR). 17 From these imaging modalities, investigators evaluated ClassicþEmbase <1947 to 2019 Week 05> Search Strategy: ------------------------------1 the response to radiotherapy with regard to several underlying variables, including lesion size, 18,21,23 density, 6,[14][15][16][17]19,20 , metabolic tumor activity, [22][23][24] and signal intensity. 25,26 Table 2 highlights the relationship between each of these underlying variables and the quantified metrics used to assess them.…”

“…The studies included for final text review investigated a variety of cancer types, sites of bone metastases, and classes of bone metastases. Among the studies selected, 6 selectively investigated specific primary cancers, 13,15,16,18,22,23 7 of 14 studies selectively investigated a site of bone metastasis, [4][5][6][7][8][9][10][11][12][13][14][15][16][17]19,21,26 and 5 studies stratified results according to class of bone metastasis. [13][14][15]17,22 A summary of these results is represented in Table 3.…”

“…Seven studies investigated the impact of palliative radiotherapy on bone density. [13][14][15][16][17]19,20 Radiographic data for density measurements were acquired through CT and XR imaging. Computed tomographic measurements of density were calculated in Hounsfield units (HU), calibrated calcium hydroxyapatite units (CaHA), and relative electron density (RED) units.…”