Meta-Analysis of STereotactic body radiothERapy in non-spine BONE metastaseS (MASTER-BONES)

PURPOSE

The efficacy and safety of stereotactic body radiation (SBRT) for patients with non-spine bone metastases (NSBM) remains in question. A systematic review and meta-analysis was performed to evaluate SBRT treatment outcomes in NSBM.

METHODS AND MATERIALS

Eligible studies were retrieved from Medline, Embase, Scielo, the Cochrane Library, and annual meeting proceedings until July 6, 2023. We adhered to the PRISMA and MOOSE guideline recommendations. Quantitative synthesis was performed using a random effects model.

RESULTS

Seven retrospective studies, with a total of 807 patients (1048 lesions) treated with stereotactic body radiation were included, with median follow-up ranging from 7.6-26.5 months. The most common stereotactic body radiation sites were pelvis (39.2%), ribs (25.8%), femur (16.7%), and humerus/shoulder region (8.7%). At 1-year, the LF and FR were 7% (95%CI 5.5-8.5%; I2=0, n= 75/1048), and 5.3% (95%CI 3-7.5%;I2=0, n= 65/1010). The 2-year cumulative LF incidence was 12.1% (95% CI: 10-15.5%). The OS and PFS at 1-year were 82% (95%CI 75-88%;I2=82%, n= 746/867), and 33.5%(95%CI 26-41%;I2=0%, n= 51/152), with a median of 20.2 months (95%CI: 10.9-49.1 months) and 8.3 months (95% CI: 6.3-10.3%) for OS and PFS, respectively. Meta-regression analysis revealed a significant relationship between planning target volume and fracture rate (p<0.05). Ribs 2.5% followed by the femur 1.9% (95%CI:0-6.1%) were the most common fracture sites. The occurrence of pain flare, fatigue and dermatitis were 7 %, 5.4 %, and 0.65 %, respectively.

CONCLUSIONS

Stereotactic body radiation proves both safety and efficacy for non-spine bone metastases and serious complications (grade 3) are infrequent. Careful consideration of target volume is crucial due to its link with a higher fracture risk.

Assessment of intrafraction motion for spine and non-spine bone metastases treated with image-guided stereotactic body radiotherapy without 6 degrees-of-freedom couch correction

Stereotactic body radiotherapy (SBRT) planning target volume (PTV) margins are influenced by multiple factors. Data is limited on intrafraction motion in bone SBRT, particularly non-spine lesions. We analyzed intrafraction motion in bone SBRT patients treated on a standard treatment couch without 6 degrees-of-freedom (6-DOF) correction. Extracranial bone SBRT patients were included. Patients were treated using two volumetric-modulated arcs and targets were localized using daily cone-beam computed tomography (CBCT) prior to each arc. Alignments between the first and second CBCT images yielded intrafraction positional shift values used to compute translational 3-dimensional vector shifts. 125 fractions from 43 patients were reviewed. Median vector shift for all SABR fractions was 0.7 mm (range 0-6.6 mm); spine 0.7 mm (range:0-2.3 mm) and non-spine 0.9 mm (range:0-6.6 mm). Of the 125 fractions, 95% had IFM vectors within the prescribed PTV margin. Intrafraction motion is small for bone SBRT patients treated on a standard couch without 6-DOF correction capabilities. Intrafraction motion was slightly larger for non-spine sites and may require treatment with larger PTV margins than spine cases.

Single-Fraction Radiotherapy (SFRT) For Bone Metastases: Patient Selection And Perspectives

Bone metastases are a frequent and important source of morbidity in cancer patients. Stereotactic body radiation therapy (SBRT) is an established treatment option for local control and pain relief of bone metastases, and it is increasingly used as upfront treatment, postoperative consolidation or salvage treatment after prior RT. However, heterogeneity of dose schedules described in literature represents a severe limitation in the definition of the role of SBRT as a standard of care. No consensus is available on the use of single versus multiple fraction SBRT for bone metastases. Advantages of single-fraction SBRT include shorter overall duration of treatment, absence of inter-fraction uncertainty, improved compliance, theoretical increased efficacy, and lower costs. However, caution has been advised due to reports of severe late toxicities, in particular, vertebral collapse fracture (VCF). The aim of this paper is to review dose fractionation and indications for the management of bone metastases using SBRT.