An international pooled analysis of SBRT outcomes to oligometastatic spine and non-spine bone metastases

Meta-Analysis of Stereotactic Body Radiation ThERapy in Nonspine BONE Metastases (MASTER-BONES)

PURPOSE

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

METHODS AND MATERIALS

Eligible studies were retrieved from MEDLINE, Embase, Scielo, the Cochrane Library, and annual meeting proceedings through July 6, 2023. We adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and Meta-analysis of Observational Studies in Epidemiology (MOOSE) guideline recommendations. Quantitative synthesis was performed using a random-effects model. Meta-regression was performed to determine correlation between clinical and treatment factors with the local failure (LF) and fracture rate. P values ≤.05 were deemed statistically significant.

RESULTS

Seven retrospective studies, with a total of 807 patients (1048 lesions) treated with SBRT were included, with median follow-up ranging from 7.6 to 26.5 months. The most common SBRT sites were pelvis (39.2%), ribs (25.8%), femur (16.7%), and humerus/shoulder region (8.7%). At 1 year, the LF and fracture rate 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 overall survival and progression-free survival 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 months) for overall survival and progression-free survival, respectively. Meta-regression analysis revealed a significant relationship between planning target volume and fracture rate (P < .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 although serious complications (grade 3) are rare, one case of grade 5 complication was reported. Careful consideration of target volume is crucial due to its link with a higher fracture risk.

Clinical Outcomes After Stereotactic Body Radiation Therapy for Nonspinal Bone Metastases: A Systematic Review and Meta-analysis

There are limited data available on clinical outcomes after stereotactic body radiation therapy (SBRT) for nonspinal bone metastases. We performed a systematic review and meta-analysis to characterize local control (LC), overall survival (OS), pain response rates, and toxicity after SBRT. The primary outcomes were 1-year LC, incidence of acute and late grade 3 to 5 toxicities, and overall pain response rate at 3 months. The secondary outcome was 1-year OS. The Newcastle-Ottawa scale was used for assessment of study bias, with a median score of 5 for included studies (range, 4-8). Weighted random-effects meta-analyses were conducted to estimate effect sizes. We identified 528 patients with 597 nonspinal bone lesions in 9 studies (1 prospective study and 8 retrospective observational studies) treated with SBRT. The estimated 1-year LC rate was 94.6% (95% CI, 87.0%-99.0%). The estimated 3-month combined partial and complete pain response rate after SBRT was 87.7% (95% CI, 55.1%-100.0%). The estimated combined acute and late grade 3 to 5 toxicity rate was 0.5% (95% CI, 0%-5.0%), with an estimated pathologic fracture rate of 3.1% (95% CI, 0.2%-9.1%). The estimated 1-year OS rate was 71.0% (95% CI, 51.7%-87.0%). SBRT results in excellent LC and palliation of symptoms with minimal related toxicity. Prospective investigations are warranted to further characterize long-term outcomes of SBRT for patients with nonspinal bone metastases.

Stereotactic body radiotherapy for distant metastases to the head and neck

PURPOSE

To report clinical outcomes for patients with metastatic disease to the head and neck (HN) treated with stereotactic body radiation therapy (SBRT).

METHODS

A retrospective review of patients treated with SBRT to HN sites from 2012 to 2020 was conducted. Treatment indications included the following: oligometastases, oligoprogression, and control a dominant area of progression (DAP). Kaplan-Meier method was used to estimate local control (LC), regional control (RC), overall survival (OS), and progression-free survival (PFS). Univariable (UVA) and multivariable analyses (MVA) were performed. Grade 3-4 acute and late toxicities were reported by the Common Terminology Criteria for Adverse Events v5.0.

RESULTS

Fifty-six patients (58 lesions) were analysed with a median follow-up of 16 months. Primary sites included lung (25.0%), kidney (19.6%), breast (19.6%) and other (35.8%). SBRT indications were as follows: oligometastases (42.9%), oligoprogression (19.6%) and local control of a dominant area of progression (37.5%). Most patients received SBRT to a single neck node (n = 47, 81.0%). Median SBRT dose was 40 Gy (range 25-50 Gy) in five fractions, with a median biologically effective dose (BED10) of 72 Gy (range 37.5-100 Gy). One- and 2-year LC and RC rates were 97.6% and 72.7% as well as 100% and 86.7%, respectively. Median OS was 19.2 months (95% [CI] 14.8-69.4), and median PFS was 7.4 months (95% [CI] 5.2-11.9). The 1-year OS and PFS rates for oligometastases, oligoprogression and DAP were 95.8%, 63.6% and 38.1% (p = 0.0039) as well as 56.5%, 27.3% and 19.1% (p = 0.0004), respectively. On MVA, treatment indication and histology were predictive for OS, while indication and prior systemic therapy were predictive for PFS. Cumulative late grade 3 + toxicity rate was 11.3%, without grade 5 events.

CONCLUSION

The use of SBRT for metastatic disease to the HN provided excellent LC rates with low rates of regional failure and an acceptable toxicity profile, highlighting its utility in these patients. Patients with oligometastatic disease had better OS and PFS than others.

Practice and principles of stereotactic body radiation therapy for spine and non-spine bone metastases

Radiotherapy is the dominant treatment modality for painful spine and non-spine bone metastases (NSBM). Historically, this was achieved with conventional low dose external beam radiotherapy, however, stereotactic body radiotherapy (SBRT) is increasingly applied for these indications. Meta-analyses and randomized clinical trials have demonstrated improved pain response and more durable tumor control with SBRT for spine metastases. However, in the setting of NSBM, there is limited evidence supporting global adoption and large scale randomized clinical trials are in need. SBRT is technically demanding requiring careful consideration of organ at risk tolerance, and strict adherence to technical requirements including immobilization, simulation, contouring and image-guidance procedures. Additional considerations include follow up practices after SBRT, with appropriate imaging playing a critical role in response assessment. Finally, there is renewed research into promising new technologies that may further refine the use of SBRT in both spinal and NSBM in the years to come.

Prospective Evaluation of the Clinical Benefits of a Novel Tattoo-less Workflow for Nonspine Bone Stereotactic Body Radiation Therapy: Integrating Surface-Guidance With Triggered Imaging Reduces Treatment Time and Eliminates the Need for Tattoos

PURPOSE

Oligometastatic disease has expanded the indications for nonspine bone stereotactic body radiation therapy (NSB SBRT). We investigated whether optical surface monitoring systems (OSMS) could enable tattoo-less setup and substitute for 2-dimensional/3-dimensional or cone beam computed tomography (CBCT)-based mid-imaging in NSB SBRT.

METHODS AND MATERIALS

OSMS was incorporated in parallel with an existing workflow using pretreatment CBCT and 2-dimensional/3-dimensional kV/kV mid-imaging beginning November 2019. The ability of OSMS to detect out-of-tolerance (>2 mm/>2°) and commanded couch shifts was analyzed. A workflow incorporating OSMS reference captures, CBCT for pretreatment verification, and OSMS/triggered imaging (TI) for intrafraction monitoring was developed for rib/sternum SBRT beginning November 2021 and all NSB SBRT beginning February 2022. Treatment time and CBCT-related radiation dose between the OSMS and the non-OSMS intrafraction monitoring group was analyzed pre- and post-OSMS/TI workflow adoption. All fractions were analyzed through statistical process control with use of an XmR chart of treatment time per quarter from February 2019 to February 2023. Special cause rules were based on Institute for Healthcare Improvement criteria.

RESULTS

From February 2019 to February 2023, 1993 NSB SBRT fractions were delivered, including 234 rib, 109 sternum, 214 ilium, and 682 multisite. Over 20 commanded shifts, OSMS could detect 2-mm shifts to within 0.4 mm 67% of the time and 0.8 mm 95% of the time. All NSB SBRT sites showed significant reductions in treatment time, including the greatest improvement in rib total treatment (21.6-13.4 minutes; P = 1.16 × 10-17) and beam time (7.9-3.2 minutes; P = 7.32 × 10-27). Significant reductions in CBCT-related radiation were also observed for several NSB sites. These process improvements were associated with OSMS adoption.

CONCLUSIONS

Adoption of a novel NSB SBRT workflow incorporating OSMS/TI for bone intrafraction motion monitoring reduced treatment time and CBCT-related radiation exposure while also allowing for more continuous intrafraction motion monitoring for NSB SBRT. OSMS/TI enabled the transition to a tattoo-less workflow.

Stereotactic body radiation therapy for bone oligometastases

Stereotactic body radiation therapy is effective for the local management of oligometastases (at most five metastases) with a benefit in survival and local control. Most studies on the management of oligometastases focus on all oligometastatic sites in primary cancer and very few focus on a single oligometastatic site. In particular, there are few data on bone oligometastases, which represent one of the preferred sites for secondary cancer locations. This article focuses on the benefit of stereotactic radiotherapy for bone oligometastases of all cancers by histological types, and reviews the results of major studies in this field.

Oncologic and Functional Outcomes After Stereotactic Body Radiation Therapy for High-Grade Malignant Spinal Cord Compression

Purpose

Although surgical decompression is the gold standard for metastatic epidural spinal cord compression (MESCC) from solid tumors, not all patients are candidates or undergo successful surgical Bilsky downgrading. We report oncologic and functional outcomes for patients treated with stereotactic body radiation therapy (SBRT) to high-grade MESCC.

Methods and Materials

Patients with Bilsky grade 2 to 3 MESCC from solid tumor metastases treated with SBRT at a single institution from 2009 to 2020 were retrospectively reviewed. Patients who received upfront surgery before SBRT were included only if postsurgical Bilsky grade remained ≥2. Neurologic examinations, magnetic resonance imaging, pain assessments, and analgesic usage were assessed every 3 to 4 months post-SBRT. Cumulative incidence of local recurrence was calculated with death as a competing risk, and overall survival was estimated by Kaplan-Meier.

Results

One hundred forty-three patients were included. The cumulative incidence of local recurrence was 5.1%, 7.5%, and 14.1% at 6, 12, and 24 months, respectively. At first post-SBRT imaging, 16.2% of patients with initial Bilsky grade 2 improved to grade 1, and 53.8% of patients were stable. Five of 13 patients (38.4%) with initial Bilsky grade 3 improved to grade 1 to 2. Pain response at 3 and 6 months post-SBRT was complete in 45.4% and 55.7%, partial in 26.9% and 13.1%, stable in 24.1% and 27.9%, and worse in 3.7% and 3.3% of patients, respectively. At 3 and 6 months after SBRT, 17.8% and 25.0% of patients had improved ambulatory status and 79.7% and 72.4% had stable status.

Conclusions

We report the largest series to date of patients with high-grade MESCC treated with SBRT. The excellent local control and functional outcomes suggest SBRT is a reasonable approach in inoperable patients or cases unable to be successfully surgically downgraded.

Safety profile of cyclin-dependent kinase (CDK) 4/6 inhibitors with concurrent radiation therapy: A systematic review and meta-analysis

The cyclin-dependent kinase 4 and 6 inhibitors (CDK4/6i) have become the standard of care for hormone receptor-positive (HR + ) and human epidermal growth factor receptor 2-negative (HER2-) metastatic breast cancer, improving survival outcomes compared to endocrine therapy alone. Abemaciclib and ribociclib, in combination with endocrine therapy, have demonstrated significant benefits in invasive disease-free survival for high-risk HR+/HER2- early breast cancer patients. Each CDK4/6i-palbociclib, ribociclib, and abemaciclib-exhibits distinct toxicity profiles. Radiation therapy (RT) can be delivered with a palliative or ablative intent, particularly using stereotactic body radiation therapy for oligometastatic or oligoprogressive disease. However, pivotal randomized trials lack information on concomitant CDK4/6i and RT, and existing preclinical and clinical data on the potential combined toxicities are limited and conflicting. As part of a broader effort to establish international consensus recommendations for integrating RT and targeted agents in breast cancer treatment, we conducted a systematic review and meta-analysis to evaluate the safety profile of combining CDK4/6i with palliative and ablative RT in both metastatic and early breast cancer settings.

Treatment of Oligometastatic Non-Small Cell Lung Cancer: An ASTRO/ESTRO Clinical Practice Guideline

PURPOSE

This joint guideline by American Society for Radiation Oncology (ASTRO) and the European Society for Radiotherapy and Oncology (ESTRO) was initiated to review evidence and provide recommendations regarding the use of local therapy in the management of extracranial oligometastatic non-small cell lung cancer (NSCLC). Local therapy is defined as the comprehensive treatment of all known cancer-primary tumor, regional nodal metastases, and metastases-with definitive intent.

METHODS

ASTRO and ESTRO convened a task force to address 5 key questions focused on the use of local (radiation, surgery, other ablative methods) and systemic therapy in the management of oligometastatic NSCLC. The questions address clinical scenarios for using local therapy, sequencing and timing when integrating local with systemic therapies, radiation techniques critical for oligometastatic disease targeting and treatment delivery, and the role of local therapy for oligoprogression or recurrent disease. Recommendations were based on a systematic literature review and created using ASTRO guidelines methodology.

RESULTS

Based on the lack of significant randomized phase 3 trials, a patient-centered, multidisciplinary approach was strongly recommended for all decision-making regarding potential treatment. Integration of definitive local therapy was only relevant if technically feasible and clinically safe to all disease sites, defined as 5 or fewer distinct sites. Conditional recommendations were given for definitive local therapies in synchronous, metachronous, oligopersistent, and oligoprogressive conditions for extracranial disease. Radiation and surgery were the only primary definitive local therapy modalities recommended for use in the management of patients with oligometastatic disease, with indications provided for choosing one over the other. Sequencing recommendations were provided for systemic and local therapy integration. Finally, multiple recommendations were provided for the optimal technical use of hypofractionated radiation or stereotactic body radiation therapy as definitive local therapy, including dose and fractionation.

CONCLUSIONS

Presently, data regarding clinical benefits of local therapy on overall and other survival outcomes is still sparse for oligometastatic NSCLC. However, with rapidly evolving data being generated supporting local therapy in oligometastatic NSCLC, this guideline attempted to frame recommendations as a function of the quality of data available to make decisions in a multidisciplinary approach incorporating patient goals and tolerances.

Predictors of pathologic fracture and local recurrence following stereotactic body radiation therapy to 505 non-spine bone metastases

PURPOSE

Stereotactic Body Radiation Therapy (SBRT) is increasingly applied to treat non-spine bone metastases (NSBM) though data remains limited on this approach. In this retrospective study, we report outcomes and predictors of local failure (LF) and pathological fracture (PF) post-SBRT for NSBM using a mature single-institution database.

METHODS

Patients with NSBM treated with SBRT between 2011 and 2021 were identified. The primary objective was to assess the rates of radiographic LF. Secondary objectives were to assess the rates of in-field PF, overall survival (OS), and late grade ≥ 3 toxicity. Competing risks analysis was used to assess rates of LF and PF. Univariable regression and multivariable regression (MVR) were performed to investigate predictors of LF and PF.

RESULTS

A total of 373 patients with 505 NSBM were included in this study. Median follow-up was 26.5 months. The cumulative incidence of LF at 6, 12, and 24 months were 5.7%, 7.9%, and 12.6%, respectively. The cumulative incidence of PF at 6, 12, and 24 months were 3.8%, 6.1%, and 10.9%, respectively. Lytic NSBM (HR = 2.18; p < 0.01), a lower biologically effective dose (HR = 1.11 per 5 Gy10 decrease; p = 0.04), and a PTV ≥ 54 cc (HR = 4.32; p < 0.01) predicted for a higher risk of LF on MVR. Lytic NSBM (HR = 3.43; p < 0.01), mixed (lytic/sclerotic) lesions (HR = 2.70; p = 0.04), and rib metastases (HR = 2.68; p < 0.01) predicted for a higher risk of PF on MVR.

CONCLUSION

SBRT is an effective modality to treat NSBM with high rates of radiographic local control with an acceptable rate of PF. We identify predictors of both LF and PF that can serve to inform practice and trial design.

Stereotactic Body Radiation Therapy for Spine Metastases-Findings from an Australian Population-Based Study

Background: To evaluate the use of stereotactic body radiation therapy (SBRT) for spine metastases and the associated factors in Australia. Methods: The Victorian Radiotherapy Minimum Dataset, which captures all episodes of radiotherapy delivered in the state of Victoria, was accessed to evaluate the patterns and trends of SBRT for spine metastases. The primary outcome was SBRT use and associated factors. Results: There were 6244 patients who received 8861 courses of radiotherapy for spine metastases between 2012 and 2017. Of these, 277 (3%) courses were SBRT, which increased from 0.4% in 2012 to 5% in 2017 (P-trend < 0.001). There was a higher proportion of SBRT use in patients with prostate cancer (6%) and melanoma (4%) compared to other cancers (2-3%) (p < 0.001). Patients from the highest socioeconomic quintiles (5%) were more likely to be treated with SBRT compared to patients from the lowest socioeconomic quintiles (3%) (p < 0.001). There was a higher proportion of SBRT use in private radiotherapy centres (6%) compared to public radiotherapy centres (1%) (p < 0.001). No spine SBRT was delivered in regional centres. In multivariate analyses, the year of treatment, age, primary cancers and radiotherapy centres were independently associated with SBRT use. Conclusion: This is the first Australian population-based study quantifying the increasing use of spine SBRT; however, the overall use of spine SBRT remains low. We anticipate an ongoing increase in spine SBRT, as spine SBRT gradually becomes the standard-of-care treatment for painful spine metastases.

Safety of CDK4/6 inhibitors and concomitant radiation therapy in patients affected by metastatic breast cancer

PURPOSE

Cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) currently represent the standard of care for the initial treatment of patients with metastatic hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2-) breast cancer. The aim of our study is to evaluate the safety of the use of concomitant radiation therapy (RT) in a consecutive series of HR+/HER2- patients treated in two academic institutions with CDK4/6i in the metastatic setting.

METHODS AND MATERIALS

From September 2017 to February 2020, we retrospectively collected and analysed data on a sequential series of patients treated with CDK4/6i, receiving RT or not, at two European institutions. Primary outcome of the study was the association between RT and any adverse events (AEs) ≥ G3. Secondary outcomes were the association between RT and any AEs (any grade), CDK4/6i dose reduction rate, and CDK4/6i treatment discontinuation rate.

RESULTS

We analysed a total of 132 consecutive women; RT was prescribed in 57 (43.2%) patients (70 irradiated lesions). The median age of the series was 52.1 years (range 32.3-78.2). Concomitant RT administration was not significantly related to higher AEs ≥ G3 (p = 0.19) and any grade AEs (p = 1.0); there was no association with RT and CDK4/6i dose reduction (p = 0.49) and discontinuation rates (p = 0.14). At a median follow-up of 18.8 months, the progression-free survival (PFS) rate was 35% and the overall survival (OS) rate was 38.7% in the whole group. The use of concomitant RT did not affect both PFS (p = 0.71) and OS rates (p = 0.55).

CONCLUSIONS

Our data are encouraging regarding the safety of this combination, showing that concurrent RT did not increase severe toxicity and did not have an impact on systemic treatment conduction.

Patient and Treatment Factors Associated with Improved Local Control and Survival in Oligometastatic Bone Disease: Results from a Large Single-Institution Experience Using Stereotactic Body Radiation Therapy

PURPOSE

Limited data exists to guide optimal patient selection and treatment of bone metastases with curative intent despite the increasing application of stereotactic body radiation therapy (SBRT) for oligometastatic (OM) disease control and re-irradiation(ReRT).

METHODS

Clinical characteristics for 434 patients consecutively treated with bone SBRT at a single institution from 3/2011-6/2020 were analyzed by OM, spine, and non-spine bone using Cox regression to determine association with local control (LC), progression-free survival (PFS), and overall survival (OS), and the Kaplan-Meier method to estimate PFS and OS.

RESULTS

Most patients had prostate (39%) or breast/lung (21%) cancer and 1-3 lesions (96%), with 651 lesions (spine 63%) treated for ReRT (12%) or OMD (88%), including synchronous (10%), metachronous (28%), repeat (27%), or induced (23%) states as defined by ESTRO/EORTC criteria. Biologically effective dose (BED₁₀) ≥50 (HR 0.68, CI 0.48-0.96, p<0.03) predicted improved LC among OM lesions and planning target volume (PTV)≥150 cc (HR 1.94, CI 1.02 to 3.70, p<0.04) predicted worse LC for non-spine bone. Prostate histology, performance status (PS) 0-1, and MFI ≥2 year predicted improved PFS and OS (p<0.05). Metachronous, synchronous, or repeat OM had higher PFS and OS (p≤0.001) than induced OM. With median follow-up 25.7 months, 1 and 2-year PFS was 63% and 47% for OM and 36% and 25% for ReRT;1 and 2-yr OS was 87% and 73% for OM, 58% and 43% for ReRT. Acute toxicities included grade 1-2 pain flare (9%) and fatigue (14%). Late toxicities included fracture (1%) for OM and myelopathy (2.5%) or nerve pain (1.2%) for ReRT.

CONCLUSIONS

BED₁₀ ≥ 50 for OM and PTV<150cc for non-spine bone lesions was associated with improved LC. Prostate histology, PS 0-1, MFI≥2 years, and metachronous, synchronous, or repeat presentations per EORTC/ESTRO OM criteria predicted improved PFS and OS among OM patients treated with bone SBRT.

Radiation myelopathy following stereotactic body radiation therapy for spine metastases

PURPOSE

Stereotactic body radiation therapy (SBRT) is now considered a standard of care treatment option in the management of spine metastases. One of the most feared complications of spine SBRT is radiation myelopathy (RM).

METHODS

We provided a narrative review of RM following spine SBRT based on review of the published literature, including data on spinal cord dose constraints associated with the risk of RM, strategies to mitigate the risk, and management options for RM.

RESULTS

There are limited published data of cases of RM following spine SBRT with detailed spinal cord dosimetry. The HyTEC report provided recommendations for the point maximal dose (Dmax) for the spinal cord that is associated with a < 5% risk of RM for 1-5 fractions spine SBRT. In the setting of spine SBRT reirradiation after previous conventional external beam radiation therapy (cEBRT), factors associated with RM are: SBRT spinal cord Dmax, cumulative spinal cord Dmax, and the time interval between previous RT and SBRT reirradiation. There are various strategies to mitigate the risk of RM, including accurate delineation of the spinal cord (or thecal sac), strict adherence to the recommended spinal cord dose constraints, and robust treatment immobilisation set-up and delivery. Limited effective treatment options are available for patients who develop RM, and these include corticosteroids, hyperbaric oxygen, and bevacizumab; however, none have been supported by high quality evidence.

CONCLUSION

RM is a rare but devastating complication following SBRT for spine metastases. There are strategies to minimise the risk of RM to ensure safe delivery of spine SBRT.

Response assessment after stereotactic body radiation therapy for spine and non-spine bone metastases: results from a single institutional study

Background

The use of stereotactic body radiation therapy (SBRT) for tumor and pain control in patients with bone metastases is increasing. We report response assessment after bone SBRT using radiological changes through time and clinical examination of patients.

Methods

We analyzed retrospectively oligo-metastatic/progressive patients with bony lesions treated with SBRT between 12/2008 and 10/2018, without in-field re-irradiation, in our institution. Radiological data were obtained from imaging modalities used for SBRT planning and follow-up purposes in picture archiving and communication system and assessed by two independent radiologists blind to the time of treatment. Several radiological changes were described. Radiographic response assessment was classified according to University of Texas MD Anderson Cancer Center criteria. Pain response and the neurological deficit were captured before and at least 6 months after SBRT.

Results

A total of 35 of the 74 reviewed patients were eligible, presenting 43 bone metastases, with 51.2% (n = 22) located in the vertebral column. Median age at the time of SBRT was 66 years (range 38–84) and 77.1% (n = 27) were male. Histology was mainly prostate (51.4%, n = 18) and breast cancer (14.3%, n = 5). Median total radiation dose delivered was 24 Gy (range 24–42), in three fractions (range 2–7), prescribed to 70–90% isodose-line. After a median follow-up of 1.8 years (range < 1–8.2) for survivors, complete or partial response, stable, and progressive disease occurred in 0%, 11.4% (n = 4), 68.6% (n = 24), and 20.0% (n = 7) of the patients, respectively. Twenty patients (57.1%) died during the follow-up time, all from disease progression, yet 70% (n = 14) from this population with local stable disease after SBRT. From patients who were symptomatic and available for follow-up, almost half (44.4%) reported pain reduction after SBRT.

Conclusions

Eighty percent of the patients showed local control after SBRT for bone metastases. Pain response was favorable. For more accurate response assessment, comparing current imaging modalities with advanced imaging techniques such as functional MRI and PET/CT, in a prospective and standardized way is warranted.

Trial registration Retrospectively registered.