Same-Day Magnetic Resonance-Guided Single-Fraction Stereotactic Body Radiation Therapy for Painful Non-Spine Bone Metastases - A Single-Center Study ("BONE SHOT")

Abstract

Introduction and background: There is evidence for efficacy of high-dose single-fraction stereotactic body radiotherapy (SF-SBRT) for painful non-spine bone metastases (NSBMs). This study ("BONE SHOT") assessed feasibility of same-day magnetic resonance-guided (MRg) planning and SF-SBRT delivery, recorded toxicity and assessed efficacy for treating metastatic patients with NSBMs.

Materials and methods: Patients with painful (≥3/10 points on a 0-10 numeric rating scale (NRS) for pain) and radiologically confirmed NSBMs from solid organ malignancies were eligible for this prospectively acquired, single-center study. Patients received MRg-SF-SBRT via MR-Linac (ViewRay®) with same-day consultation, consent, planning and treatment. Drop-out rate, procedure times, acute toxicity and pain response were recorded.

Results: Between June 2019 and June 2020, 13 patients with 15 NSBMs were treated per protocol. Mean patient age was 64 (range, 30-87) years; most common primary cancer was gastrointestinal malignancies (38.5 %); most commonly treated site was pelvis (53.3 %). All workflows were completed as planned. Median on-table time for contouring, planning and delivery was 65 (range, 57-112) minutes. Treatments were well tolerated; one patient developed "pain flair"; no grade ≥ 3 toxicities were registered. At one week following SBRT, overall and complete pain response rates were 73.3 % and 20.0 %, respectively, which evolved to 66.7 % and 53.3 % at four weeks after SBRT; median pre-treatment pain score was 6 points, which was reduced by a median of 5 points (P = 0.0028) at four weeks.

Conclusion: The same-day MRg-SF-SBRT workflow for NSBMs was feasible, safe, and preliminary results indicate promising efficacy, warranting future trials investigating this intervention.

Keywords: Bone metastases; MR-Linac; Palliative radiotherapy; SBRT.

Fig. 1

Workflow for Same-Day Magnetic Resonance-Guided Single-Fraction Stereotactic Body Radiation Therapy. Abbreviations: CT = Computer tomography; MRI = Magnetic resonance imaging; MRIdian = Hybrid MR-Linac by ViewRay; QA = Quality assurance.

Fig. 2

Pain response over time. Abbreviations: NRS = Numeric rating scale.Notes: Pain classified on 10-point NRS, with 0 = “no pain” and 10 = “Worst imaginable pain”.

Fig. 3a

Example case – Diagnostic, axial CT image for “dummy treatment plan” creation. Abbreviations: CT = Computer tomography.Notes: Based on a diagnostic CT image, the treating radiation oncologist indicated the lesion to treat; treatment planners developed a dummy treatment plan.

Fig. 3b

Example case – Axial slice of treatment plan of 12 Gy SF-SBRT of left hip lesion. Abbreviations: CT = Computer tomography; SF = Single fraction; SBRT = Stereotactic body radiation therapy. Notes: At the time of on-table treatment simulation, the CT-based dummy treatment plan was improved before treatment was approved by radiation oncologist and medical physicist.