Elsevier

Practical Radiation Oncology

Volume 10, Issue 6, November–December 2020, Pages e452-e460
Practical Radiation Oncology

Basic Original Report
Stereotactic Body Radiation Therapy for Nonspine Bone Metastases: International Practice Patterns to Guide Treatment Planning

https://doi.org/10.1016/j.prro.2020.02.011Get rights and content

Abstract

Purpose

Stereotactic body radiation therapy (SBRT) is increasingly used for nonspine bone metastases (NSBM); however, there are limited data informing treatment planning. We surveyed international experts to better understand worldwide practice patterns in delivering NSBM-SBRT.

Methods and Materials

Nine international radiation oncologists were invited to participate based on demonstrated expertise with NSBM-SBRT. Experts were sent gross tumor volume contours and planning computed tomography and magnetic resonance images for 11 NSBM cases that covered a range of bony sites, including metastases to long bones (femur, humerus), pelvic bones (ilium, ischium, acetabulum, pubic symphysis), and thoracic bones (rib, sternum, scapula, clavicle). Experts were surveyed regarding treatment planning decisions and dose-fractionation selection. Descriptive analysis was conducted on the survey data.

Results

All experts participated and completed the survey. Most (56%) routinely fused magnetic resonance imaging with planning computed tomography imaging for target delineation. Dose fractionation schedules included single-fraction (18-24 Gy/1), 2 fractions (24 Gy/2), 3 fractions (28-30 Gy/3), 5 fractions (30-50 Gy/5), and 10 fractions (42-50 Gy/10). Although doses varied considerably, all had a biological equivalent dose of ≤100 Gy10. Five-fraction schedules were most common, specifically 35 Gy/5, with 56% opting for this dose-fractionation in at least 1 case. Other dose-fractionation schedules used by at least 3 experts were 20 Gy/1, 30 Gy/3, and 30 Gy/5. Three experts prescribed 2 dose volumes using a simultaneous integrated boost. The 2 dose volumes were either the gross tumor volume and clinical target volume (CTV) or a smaller CTV (CTV1) encompassed within a larger CTV (CTV2) (eg, 30 Gy/3 to gross tumor volume or CTV1 and 15-24 Gy/3 to CTV or CTV2). Dose de-escalation was recommended by all experts in the setting of previous SBRT and by most in the context of previous convevoltherapy or in weight-bearing bones, especially if moderate-to-severe cortical erosion was present.

Conclusions

Significant heterogeneity exists worldwide in radiation technique and dose-fractionation for NSBM-SBRT, which supports the need for consensus guidelines to inform practice and trial design. Nonetheless, these data demonstrate expert agreement on selecting dose schedules with a biologically effective dose ≤100 Gy10, reasons for dose de-escalation, and in determining acceptable dose schedules based on bony site.

Introduction

Accumulating evidence favors stereotactic body radiation therapy (SBRT) over conventional palliative radiation therapy (cRT) for bone metastases, particularly in the oligometastatic setting.1, 2., 3 Currently, nonspine bone metastases (NSBM) reports in the literature are limited, with a recent systematic review of bone SBRT revealing only 8 of the 57 analyzed studies included NSBM and merely 2 studied an NSBM population exclusively.4 A recent phase II trial showed improved pain response rates with single-fraction SBRT compared with cRT.1 However, the method of target delineation was not clear and the SBRT doses selected were based on an institutional protocol alone. Herein, we surveyed international radiation oncologists with expertise in NSBM-SBRT to better understand worldwide practice patterns to inform clinical management and future research.

Section snippets

Methods and Materials

Nine radiation oncologists representing Canada, the United States, Australia, Switzerland, the Netherlands, and Korea were invited to participate based on expertise in delivering NSBM-SBRT demonstrated through publications or clinical experience. Experts were sent the treatment planning computed tomography (CT) and magnetic resonance images (MRIs) for each of the 11 NSBM cases with the gross tumor volume (GTV) contoured. Cases were purposefully selected to represent a range of bony sites,

Results

All experts agreed to participate and the survey completion rate was 100%.

Discussion

We demonstrate significant heterogeneity worldwide in the delivery of NSBM-SBRT, particularly with respect to treatment technique and dose. Although this highlights the need for guidelines to inform clinical practice and trial design, there were areas of agreement that can guide treating radiation oncologists in the meantime. All experts prescribed a BED of ≤100 Gy10, and >50% of selected dose fractionations had a BED of 60 Gy10. Other practice similarities shared by a majority of surveyed

Conclusions

Significant heterogeneity exists in international radiation techniques and dose-fractionations for NSBM-SBRT, which supports the need for clinical trials and consensus guidelines. Nonetheless, these data demonstrate expert agreement on selecting dose schedules with a BED ≤ 100 Gy10, reasons for dose de-escalation, and in determining acceptable dose schedules based on bony site.

Cited by (23)

  • Stereotactic Body Radiation Therapy for Metastases in Long Bones

    2022, International Journal of Radiation Oncology Biology Physics
    Citation Excerpt :

    We observed local failure in 9 of the 110 metastases (8.2%), and the median time to local failure after SBRT was long, 28 months (range, 4-48 months). Cumulative incidence of local failure of 13.5% at 3 years is comparable with local failure rates after SBRT for metastases in other nonspine bones,12,13 which is expected considering the use of sufficiently high radiation doses in our study.14 Increased post-SBRT bone remodeling, recalcification, and reossification reported previously15,16 might also contribute to the low incidence of pathologic fracture.

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Data sharing: Research data are stored in an institutional repository and will be shared upon request to the corresponding author.

Sources of support: No funding was obtained for this study.

Disclosures: Dr Eppinga reports personal fees from Elekta, outside the submitted work. Dr Lo reports grants from Elekta AB, outside the submitted work, and he was a part of the Gamma Knife ICON expert group. Dr Redmond reports grants and personal fees from Accuray, grants and personal fees from Elekta, personal fees from BioMimetix, and personal fees from Brainlab outside the submitted work. Dr Arjun Sahgal has been an advisor/consultant with Abbvie, Merck, Roche, Varian (Medical Advisory Group), and Elekta (Gamma Knife Icon); is an ex officio board member on the board of the International Stereotactic Radiosurgery Society (ISRS); received honorarium for past educational seminars with Elekta AB, Accuray Inc, Varian (CNS Teaching Faculty), BrainLAB, and Medtronic Kyphon; received a research grant from Elekta AB; and had travel accommodations/expenses paid by Elekta, Varian, and BrainLAB. Dr Sahgal also belongs to the Elekta MR Linac Research Consortium, Elekta Spine, and Oligometastases and Linac Based SRS Consortia. Dr Siva reports grants from Varian Industries; grants from Merck-Sharp-Dohme; grants, personal fees, and other from Astra Zeneca; personal fees from Bristol Meyer Squibb; personal fees from Astellas; personal fees from Janssen; and personal fees from Roche outside the submitted work. Dr Dagan reports personal fees from Elekta and personal fees from UptoDate outside the submitted work. Dr. Tseng reports travel accommodations/expenses and honoraria for past educational seminars by Elekta, belongs to the Elekta MR Linac Research Consortium, and has been an advisor/consultant for Sanofi.

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