Phase I/II study of stereotactic body radiotherapy for spinal metastasis and its pattern of failure

Dose-intensified SBRT for vertebral oligometastases: results from a prospective clinical trial

PURPOSE

To prospectively evaluate safety and efficacy of dose-intensified multifraction SBRT using a simultaneous-integrated boost concept for vertebral oligometastases.

MATERIAL AND METHODS

Data from 128 patients with 143 vertebral oligometastases (≤5 distant metastases in total) treated with dose-intensified SBRT (48.5 Gy/10 [with epidural involvement] or 40 Gy/5 [without epidural involvement]) in the randomized and non-randomized arms of a phase 3 clinical trial conducted at 18 international centers between 2016 and 2023 were analyzed.

RESULTS

The median age of all patients was 68 years; 77 patients (60.2%) had breast and prostate cancer. Of 143 vertebral metastases, 23 (16.1%) and 22 metastases (15.4%) had epidural and paraspinal tumor involvement, respectively. The median follow-up time was 24 months. At 2 years, cumulative incidence of local failure (4 failures) was 5.3%. There were 4 (2.8%) baseline and 8 (5.6%) de novo vertebral compression fractures (VCFs). Two-year OS was 82.2% (95% CI, 74.9-89.6%). There was no grade ≥ 4 adverse events (AE) and the crude rate of grade 3 AEs was 5.5%; no myelopathy or plexopathy was observed. On multivariate analysis, only non-breast or non-prostate cancer (HR, 7.91; 95%, CI 1.79-35.03; 2-sided P = 0.01) were found to be prognostic for adverse OS. No prognostic factors for VCF were identified. Epidural and paraspinal involvement were not found to be prognostic for treatment outcome.

CONCLUSIONS

Dose-intensified SBRT for vertebral oligometastases is effective and safe, even in high-risk patients with epidural or paraspinal involvement.

Integrated management of metastatic spinal tumors: current status and future directions

With improved cancer survivorship, the incidence of metastatic bone disease has risen, and metastatic spinal tumors (MSTs) have emerged as a common yet significant clinical challenge. These tumors may compromise the integrity of vertebral bodies leading to pathological fractures and neurological compromise from nerve root or spinal cord compression dramatically affecting the patient's quality of life. Despite the associated morbidity and mortality, optimal treatment strategies remain elusive. Here, in our review, we provide a comprehensive analysis of the contemporary MST treatment strategies, encompassing surgical interventions, advanced radiotherapy modalities, and evolving systemic therapies including chemotherapeutic and immunotherapeutic approaches. We critically evaluate each modality's development trajectory, clinical efficacy, therapeutic advantages, and inherent limitations. Our analysis reveals a definitive shift toward precision-guided radiotherapy and minimally invasive surgical techniques that balance therapeutic efficacy with reduced morbidity. These findings underscore the necessity for multidisciplinary management and highlight promising avenues for therapeutic innovation. As treatment paradigms evolve, integration of these advanced modalities offers new hope for this vulnerable patient population facing a challenging oncological complication.

Stereotactic Body Radiation Therapy Alone or in Combination with Immunotherapy in Kidney Cancer: A Systematic Review

BACKGROUND AND OBJECTIVE

Despite its radioresistant reputation, renal cell carcinoma (RCC) is sensitive to high dose per fraction stereotactic ablative body radiotherapy (SABR). As SABR also triggers immunomodulatory effects, a combination of SABR and immunotherapy for RCC might improve patient outcomes. The current systematic review will discuss all prospective studies on SABR alone or combined with immunotherapy.

METHODS

A systematic review was conducted in January 2025 according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses statement on the PubMed and Cochrane databases. Thirty-eight studies were included in this review.

KEY FINDINGS AND LIMITATIONS

In the primary setting, 15 prospective studies have proved SABR to be a valuable alternative for (partial) nephrectomy for high-risk or medically inoperable patients, with good tolerability and excellent local control. No prospective studies have reported on SABR combined with immunotherapy in nonmetastatic patients. In the oligometastatic setting, two phase 2 trials have investigated SABR in lieu of systemic treatment. This showed encouraging results, with the majority of patients being free from systemic therapy at 1 yr. SABR combined with immunotherapy in the metastatic setting has been investigated in multiple phase 1 and 2 trials, where the most promising option seems to be SABR to multiple-preferentially all-lesions. Cytoreductive SABR and SABR to oligoprogressive lesions combined with immunotherapy are attractive future strategies.

CONCLUSIONS AND CLINICAL IMPLICATIONS

SABR is a valid alternative in localised RCC when (partial) nephrectomy is not an option. In the metastatic setting, several early-phase trials have investigated SABR alone and in combination with immunotherapy, warranting future large, randomised trials.

Separation Surgery Followed by Conformal Postoperative Spine Stereotactic Body Radiation Therapy Does Not Increase Risk of Adjacent Spine Level Progression in the Management of Spine Metastases

OBJECTIVE

To determine if piecemeal separation surgery, in conjunction with smaller treatment volumes utilized with spine stereotactic radiation therapy (S-SBRT), increased the risk of adjacent level progression (ALP).

METHODS

We performed a retrospective analysis of a prospectively maintained database of adult spine oncologic patients who underwent SBRT to the spine at University of Michigan from 2010 to 2021. We compared ALP in patients undergoing SBRT who had pretreatment surgery with those who did not.

RESULTS

Four hundred and ninety-eight treatment sites were identified in 417 patients. Of these, 366 (73.5%) were treated with SBRT alone and 132 (26.5%) were treated with surgery followed by S-SBRT. Patients treated with SBRT alone were significantly older (63.3 y) compared with the surgery plus SBRT group (60.2 y; P =0.02). More radiosensitive histologies were treated with SBRT alone (34%) compared with 11% for the surgery plus SBRT group ( P <0.001). Lesions treated in the surgery plus SBRT group had significantly more severe metastatic epidural spinal cord compression (65%) compared with the SBRT only group (8%) ( P <0.001). Both infield progression (9.3% vs. 7.6%; P =0.43) and ALP (21.3% vs. 18.9%; P =0.37) were not significantly different between groups.

CONCLUSIONS

Spine oncology patients treated with surgery followed by conformal postoperative S-SBRT had similar infield and ALP compared with patients receiving SBRT alone, suggesting that piecemeal separation surgery does not locally spread tumor cells, leading to an increased risk of ALP failure, and supporting the use of conformal postoperative S-SBRT.

A systematic review of stereotactic radiosurgery for metastatic spinal sarcomas

PURPOSE

Sarcomas metastasizing to the spine are a rare entity. Ideally an En-bloc resection is necessary to achieve durable local control (LC) rates. However, anatomical constraints often limit the degree of tumor resection. Because of this, other therapeutic modalities either replacing or as an adjuvant to resection are necessary. Stereotactic radiosurgery (SRS) is a reasonable candidate therapy.

METHODS

We conducted a systematic review of the literature using the following databases: PubMed, Science Direct, and Cochrane library. We used a combination of the following terms connected by boolean operators: "Metastatic Sarcoma, Sarcoma of the Spine, Spine Sarcoma, Metastasis, stereotactic radiosurgery, SRS." All retrospective and prospective cohorts, as well as randomized control trials reporting on patients with histopathologically confirmed metastatic sarcomas of the bony elements of the vertebrae, thecal sac, cord, or associated soft tissues of the spine were included. We excluded animal studies, case reports, case series, patients < 18 (pediatric cohorts), review articles and meta-analyses. No date filters were applied to our search.

RESULTS

Our final analysis included 5 studies ranging from 2009 to 2024 reporting on 260 patients and 371 associated lesions. Leiomyosarcoma was the most frequently reported histologic subtype (60%). Most lesions were localized to the thoracic spine (48.6%). 75% of studies reported a median dose < 30 Gy, and achieved biologically equivalent doses (BEDs) ranging from < 50-100. Pooled 1-year median survival was 64.5% (IQR: 61.8-75.10). Pooled 1-year median LC was 86% (IQR: 79.4-88.5). Three of five studies (60%) for OS and 4/5 (80%) for LC had data availability suitable for meta-analysis. The 1-year OS and LC rates proportions across these studies were 67% (proportion = 0.67, 95% CI: 0.57-0.75, p = 0.07, I2 = 63%), and 84% (proportion = 0.84, 95% CI: 0.78-0.89, p = 0.10, I2 = 52%) respectively. Median follow up across all studies was 18 months (IQR:12.7-31.3).

CONCLUSIONS

SRS is a reasonable alternative therapy in either the up front, salvage or adjuvant setting which can facilitate durable LC.

Patterns of failure after stereotactic body radiotherapy to non-spine bone metastases

BACKGROUND AND PURPOSE

Stereotactic body radiotherapy (SBRT) has proven useful for non-spine bone metastases (NSBM). We analyzed local relapse rates and patterns of failure after NSBM-SBRT, contrasting our results with existing contouring guidelines.

MATERIALS AND METHODS

We conducted a retrospective analysis of NSBM-SBRT treatments performed between 2013 and 2024 in a single institution. Clinical, pathologic, and treatment-related data were collected. Failure patterns were assessed based on imaging tests and categorized as in-field, marginal/out-of-field.

RESULTS

Among 119 NSBM-SBRT treatments in 85 patients, the most common primary tumors were prostate (36.1%) and breast cancer (24.4%). The coxal bone was the predominant metastatic site (52.9%). The median follow-up was 32.8 months. OS rates at 1, 2, and 3 years were 90.1%, 83.5%, and 75.8%, respectively. Twenty seven relapses were observed in the treated bone with a median recurrent tumor volume of 9.9 cm3 and a median time to recurrence of 15.1 months. Relapse-free survival in the treated bone was 89.4%, 78.5%, and 74.2% at 1, 2, and 3 years, respectively. Median recurrent tumor volume within the CTV was 50.6% and the median distance from the relapse center to the initial tumor was 11.4 mm.

CONCLUSION

NSBM-SBRT provides effective local control with relapses often occurring near the initial tumor lesion. While adherence to existing contouring guidelines captures most scenarios, consideration of larger CTV expansions may be warranted in cases with poorer prognosis. Further studies are needed to identify risk factors for relapses outside the margins and optimize volume delineation in these scenarios.

Use of Carbon Fiber Implants to Improve the Safety and Efficacy of Radiation Therapy for Spine Tumor Patients

Current standard of care treatment for patients with spine tumors includes multidisciplinary approaches, including the following: (1) surgical tumor debulking, epidural spinal cord decompression, and spine stabilization techniques; (2) systemic chemo/targeted therapies; (3) radiation therapy; and (4) surveillance imaging for local disease control and recurrence. Titanium pedicle screw and rod fixation have become commonplace in the spine surgeon's armamentarium for the stabilization of the spine following tumor resection and separation surgery. However, the high degree of imaging artifacts seen with titanium implants on postoperative CT and MRI scans can significantly hinder the accurate delineation of vertebral anatomy and adjacent neurovascular structures to allow for the safe and effective planning of downstream radiation therapies and detection of disease recurrence. Carbon fiber-reinforced polyetheretherketone (CFR-PEEK) spine implants have emerged as a promising alternative to titanium due to the lack of artifact signals on CT and MRI, allowing for more accurate and safe postoperative radiation planning. In this article, we review the tenants of the surgical and radiation management of spine tumors and discuss the safety, efficacy, and current limitations of CFR-PEEK spine implants in the multidisciplinary management of spine oncology patients.

Radiation therapy, radiosurgery, chemotherapy and targeted therapies for metastatic spine tumors: WFNS Spine committee recommendations

OBJECTIVE

This review aims to formulate the most current, evidence-based recommendations regarding radiation therapy, radiosurgery, and chemotherapy for patients with metastatic spine tumors.

METHODS

A systematic literature using PRISMA methodology was performed from 2010-2023 using the search terms "radiosurgery," "radiation therapy," "external beam radiation therapy," or "stereotactic body radiation therapy" in conjunction with "spinal," "spine," "metastasis," "metastases," or "metastatic."

RESULTS

Spinal metastases should be managed in a multidisciplinary team consisting of spine surgeons, radiation oncologists, radiologists and oncologists. Patients identified as potential candidates for SRS/EBRT using internationally recognized frameworks and criteria should be assessed by surgeons to see if surgical cyto-reduction/ separation surgery can be achieved. Choices for treatment of recurrence include re-irradiation with SBRT vs EBRT, surgical debulking, additional chemotherapy or palliative care. There is a lack of current clinical evidence to support the routine use of targeted therapies in the management of metastatic spinal tumors.

CONCLUSIONS

Improving the management of spinal metastasis will lead to increased quality of life and improved survival. This review provides current, evidence-based guidelines on radiation therapy, radiosurgery, and chemotherapy for patients with metastatic spine tumors.

Shifting the Landscape of Spine and Non-Spine Bone Metastases: A Review of Stereotactic Body Radiotherapy

ABSTRACT

Both spine and nonspine bone metastases are frequent sites of spread from solid organ malignancies. As bone metastases frequently cause significant morbidity for patients, it is critical to offer a treatment that can achieve rapid and durable symptomatic relief and local control, without being associated with serious risks of toxicity. Conventional palliative radiation therapy has a key treatment component in the multidisciplinary management of these patients; however, over the past decade, it has evolved to routinely deliver high biologically effective doses with precision in the form of stereotactic body radiation therapy. This change in paradigm is a result of the shifting landscape in cancer care, such that short-term pain relief is no longer the sole therapeutic aim for selected patients, and durable symptom relief and local tumor control are the goals. This review discusses the randomized prospective evidence, ongoing trials, approach to surveillance imaging, and treatment delivery for stereotactic body radiation therapy, to both spine and nonspine bone metastases, with a specific section on sacral metastases.

Stereotactic body radiotherapy for treatment of spinal metastasis: A systematic review of the literature

Background

Advances in local and systemic therapies continue to improve overall survival for patients with cancer, increasing the incidence of spine metastases. Up to 15% of patients with solid tumors develop spinal metastases. Spinal metastases can be particularly devastating for quality of life given the potential pain, neurological deficits from spinal cord compression or cauda equina syndrome, spinal instability, and pathological fractures that may result. Stereotactic body radiotherapy (SBRT) with or without adding less invasive surgical techniques for stabilization or separation has gained favor. SBRT uses smaller, more precise treatment volumes, allowing for higher doses per fracture, thus increasing ablative abilities.

Methods

We conducted a systematic review using MEDLINE, Embase (Elsevier), and Web of Science to identify all articles investigating the effectiveness of SBRT in providing local disease control, pain control, and relief of spinal cord compression for patients with metastatic disease of the spine.

Results

The review yielded 84 articles that met inclusion criteria. The evidence indicates SBRT provides excellent local control and pain control for patients with spine metastesis, and this remains true for patients with spinal cord compression managed with surgical separation followed by postoperative spine SBRT.

Conclusion

While not all patients are appropriate candidates for SBRT, carefully considering appropriate frameworks that consider the patient's overall prognosis can guide a multidisciplinary team toward the patients who will benefit the most from this treatment modality.

Impacts of radiation therapy on quality of life and pain relief in patients with bone metastases

Bone metastases (BM) are a common complication in advanced cancer patients, significantly contributing to morbidity and mortality due to their ability to cause pain, fractures, and spinal cord compression. Radiation therapy (RT) is vital in managing these complications by targeting metastatic lesions to ease pain, improve mobility, and reduce the risk of skeletal-related events such as fractures. Evidence supports the effectiveness of RT in pain relief, showing its ability to provide significant palliation and lessen the need for opioid painkillers, thereby enhancing the overall quality of life (QoL) for patients with BM. However, optimizing RT outcomes involves considerations such as the choice of radiation technique, dose fractionation schedules, and the integration of supportive care measures to mitigate treatment-related side effects like fatigue and skin reactions. These factors highlight the importance of personalized treatment planning tailored to individual patient needs and tumor characteristics. This mini-review aims to provide comprehensive insights into the multifaceted impacts of RT on pain management and QoL enhancement in BM patients, with implications for refining clinical practices and advancing patient care through the synthesis of findings from various studies.

Radiation Therapy for Primary and Metastatic Spine Tumors

Radiation therapy plays an important role in the management of patients with primary and metastatic spine tumors. Technological innovations in the past decade have allowed for improved targeting, dose escalation, and precision of radiation therapy while concomitant improvements in surgical techniques have resulted in improved outcomes with reduced morbidity. Patients with cancer have increasingly complex oncologic needs, and multidisciplinary management is more essential than ever. This review will provide an overview of radiation principles, modern radiation techniques, management algorithms, and expected toxicities of common radiation treatments in the management of spine tumors.

Stereotactic Radiosurgery in Metastatic Spine Disease-A Systemic Review of the Literature

BACKGROUND

This study investigated the efficacy of stereotactic radiosurgery (SRS) in managing spinal metastasis. Traditionally, surgery was the primary approach, but SRS has emerged as a promising alternative.

OBJECTIVE

The study aims to evaluate the efficacy of stereotactic radiosurgery in the management of spinal metastasis in terms of local tumor control, patient survival, and quality of life, identifying both advantages and limitations of SRS.

METHODS

Through an extensive literature search in PubMed with cross-referencing, relevant full-text-available papers published between 2012 and 2022 in English or German were included. The search string used was "metastatic spine diseases AND SRS OR stereotactic radiosurgery".

RESULTS

There is growing evidence of SRS as a precise and effective treatment. SRS delivers high radiation doses while minimizing exposure to critical neural structures, offering benefits like pain relief, limited tumor growth, and a low complication rate, even for tumors resistant to traditional radiation therapies. SRS can be a primary treatment for certain metastatic cases, particularly those without spinal cord compression.

CONCLUSIONS

SRS appears to be a preferable option for oligometastasis and radioresistant lesions, assuming there are no contraindications. Further research is necessary to refine treatment protocols, determine optimal radiation dose and fractionation schemes, and assess the long-term effects of SRS on neural structures.

Magnetic Resonance Imaging Frequency After Stereotactic Body Radiation Therapy for Spine Metastases

PURPOSE

Stereotactic body radiation therapy (SBRT) is increasingly being used to treat spine metastases. Current post-SBRT imaging surveillance strategies in this patient population may benefit from a more data-driven and personalized approach. The objective of this study was to develop risk-stratified post-SBRT magnetic resonance imaging (MRI) surveillance strategies using quantitative methods.

METHODS AND MATERIALS

Adult patients with bony spine metastases treated with SBRT between 2008 and 2021 and who had at least 2 follow-up spine MRIs were reviewed retrospectively. A recursive partitioning analysis model was developed to separate patients into different risk categories for post-SBRT progression anywhere within the spine. Imaging intervals were derived for each risk category using parametric survival regression based on multiple expected spine progression rates per scan.

RESULTS

A total of 446 patients and 1039 vertebral segments were included. Cumulative incidence of spine progression was 19.2% at 1 year, 26.7% at 2 years, and 35.3% at 4 years. The internally validated risk stratification model was able to divide patients into 3 risk categories based on epidural disease, paraspinal disease, and Spinal Instability Neoplastic Score category. The 4-year risk of spine progression was 23.4%, 39.0%, and 51.8%, respectively, for the low-, intermediate-, and high-risk groups. Using an expected per-scan spine progression rate of 3.75%, the low-risk group would require follow-up scans every 6.0 months (95% CI, 4.9-7.6) and the intermediate-risk group would require surveillance every 3.1 months (95% CI, 2.6-3.7). At an expected spine progression rate of 5%, the high-risk group would require surveillance every 1.3 months (95% CI, 1.1-1.6) during the first 13.2 months after SBRT and every 5.9 months thereafter (95% CI, 2.8-12.3).

CONCLUSIONS

Data-driven follow-up MRI surveillance intervals at a range of expected spine progression rates have been determined for patients at different risks of spine progression based on an internally validated, single-institution risk stratification model.

Management of Metastatic Spinal Disease - A Practical Approach

STUDY DESIGN

Narrative review.

OBJECTIVE

This review presents a comprehensive approach to the management of spinal metastases.

METHODS

N/A.

RESULTS

The wide spectrum of clinical presentation in spinal metastases necessitates a personalized approach to treatment planning. This includes a comprehensive diagnostic workup, oncological management, palliation of symptoms, and surgical intervention if appropriate. A systematic and multidisciplinary approach allows optimal shared decision making to reach an evidence-informed and value-congruent treatment plan for the patient. We highlight how advances in stereotactic body radiotherapy (SBRT) and separation surgery may be incorporated into clinical management from a spine surgeon's perspective.

CONCLUSION

This review summarizes the approach and management of spinal metastases, its outcomes and complications.

Stereotactic Body Radiation Therapy for Sacral Metastases: Deviation From Recommended Target Volume Delineation Increases the Risk of Local Failure

PURPOSE

Although spine stereotactic body radiation therapy (SBRT) is considered a standard of care in the mobile spine, mature evidence reporting outcomes specific to sacral metastases is lacking. Furthermore, there is a need to validate the existing sacral SBRT international consensus contouring guidelines to define the optimal contouring approach. We report mature rates of local failure (LF), adverse events, and the effect of contouring deviations in the largest experience to date specific to sacrum SBRT.

METHODS AND MATERIALS

Consecutive patients who underwent sacral SBRT from 2010 to 2021 were retrospectively reviewed. The primary endpoint was magnetic resonance imaging-based LF with a focus on adherence to target volume contouring recommendations. Secondary endpoints included vertebral compression fracture and neural toxicity.

RESULTS

Of the 215 sacrum segments treated in 112 patients, most received 30 Gy/4 fractions (51%), 24 Gy/2 fractions (31%), or 30 Gy/5 fractions (10%). Sixteen percent of segments were nonadherent to the consensus guideline with a more restricted target volume (undercontoured). The median follow-up was 21.4 months (range, 1.5-116.9 months). The cumulative incidence of LF at 1 and 2 years was 18.4% and 23.1%, respectively. In those with guideline adherent versus nonadherent contours, the LF rate at 1 year was 15.1% versus 31.4% and at 2 years 18.8% versus 40.0% (hazard ratio [HR], 2.5; 95% CI, 1.4-4.6; P = .003), respectively. On multivariable analysis, guideline nonadherence (HR, 2.4; 95% CI, 1.3-4.7; P = .008), radioresistant histology (HR, 2.4; 95% CI, 1.4-4.1; P < .001), and extraosseous extension (HR, 2.5; 95% CI, 1.3-4.7; P = .005) predicted for an increased risk of LF. The cumulative incidence of vertebral compression fracture was 7.1% at 1 year and 12.3% at 2 years. Seven patients (6.3%) developed peripheral nerve toxicity, of whom 4 had been previously radiated.

CONCLUSIONS

Sacral SBRT is associated with high efficacy rates and an acceptable toxicity profile. Adhering to consensus guidelines for target volume delineation is recommended to reduce the risk of LF.

Efficacy of flattening filter-free beams with the acuros XB algorithm in thoracic spine stereotactic body radiation therapy

This study aimed to determine the dosimetric value of flattening filter-free (FFF) beams compared to flattening filter (FF) beams using different algorithms in the treatment planning of thoracic spine stereotactic body radiation therapy (SBRT). A total of 120 plans were created for 15 patients using the Anisotropic Analytical Algorithm (AAA) and the Acuros External Beam (AXB) algorithm with FF and FFF beams at 6 MV and 10 MV energies. Various dosimetric parameters were evaluated, including target coverage, dose spillage, and organs-at-risk sparing of the spinal cord and esophagus. Treatment delivery parameters, such as the monitor units (MUs), modulation factors (MFs), beam-on time (BOT), and dose calculation time (DCT), were also collected. Significant differences were observed in the dosimetric parameters when AXB was used for all energies (P < 0.05). 6 XFFF energy was the best option for target coverage, dose spillage, and organs-at-risk sparing. In contrast, dosimetric parameters had no significant difference when using the AAA. The AAA and AXB calculations showed that the 6 XFFF beam had the shortest DCT. The treatment delivery parameters indicated that 10 XFF beam required the fewest MUs and MFs. In addition, the 10 XFFF beam demonstrated the shortest BOT. For effective treatment of the thoracic spine using SBRT, it is recommended to use the 10 XFFF beam because of the short BOT. Moreover, the AXB algorithm should be used because of its accurate dose calculation in regions with tissue heterogeneity.

Stereotactic body radiation therapy versus conventional external beam radiotherapy for spinal metastases: A systematic review and meta-analysis of randomized controlled trials

INTRODUCTION

This study aimed to compare SBRT and cEBRT for treating spinal metastases through a systematic review and meta-analysis of randomized controlled trials (RCTs).

METHODS

PubMed, EMBASE and Cochrane Library were searched up to 6 May 2023 for RCTs comparing SBRT and cEBRT for spinal metastases. Overall and complete pain response, local progression, overall survival, quality of life and adverse events were extracted. Data were pooled using random-effects models. Results were reported as risk ratios (RRs) for dichotomous outcomes, and hazard ratios (HRs) for time-to-event outcomes, along with their 95% confidence intervals (CIs). Heterogeneity was evaluated using the I2 statistic.

RESULTS

Three RCTs were identified involving 642 patients. No differences were seen in overall pain response comparing SBRT and cEBRT (RR at 3 months: 1.12, 95% CI, 0.74-1.70, p = 0.59; RR at 6 months: 1.29, 95% CI, 0.97-1.72, p = 0.08). Only two of three studies presented complete pain response data. SBRT demonstrated a statistically significant improvement in complete pain response compared to cEBRT (RR at 3 months: 2.52; 95% CI, 1.58-4.01; P < 0.0001; RR at 6 months: 2.48; 95% CI, 1.23-4.99; P = 0.01). There were no significant differences in local progression and overall survival. Adverse events were similar, except for any grade radiation dermatitis, which was significantly lower in SBRT arm (RR 0.17, 95% CI 0.03-0.96, P = 0.04).

CONCLUSION

SBRT is a safe treatment option for spine metastases. It may provide better complete pain response compared to cEBRT. Additional trials are needed to determine the potential benefits of SBRT in specific patient subsets.

Spinal Reirradiation-Mediated Myelopathy: A Systematic Review and Meta-Analysis

Reirradiation of the spine is carried out in 42% of patients who do not respond to treatment or have recurrent pain. However, there are few studies and data on the effect of reirradiation of the spine and the occurrence of acute and chronic side-effects caused by reirradiation, such as myelopathy, in these patients. This meta-analysis aimed to determine the safe dose in terms of biological effective dose (BED), cumulative dose and dose interval between BED1 and BED2 to decrease or prevent myelopathy and pain control in patients undergoing radiation therapy in the spinal cord. A search was carried out using EMBASE, MEDLINE, PUBMED, Google Scholar, Cochrane Collaboration library electronic databases, Magiran, and SID from 2000 to 2022 to recognise qualified studies. In total, 17 primary studies were applied to estimate the pooled effect size. The random effects model showed that the pooled BED in the first stage, the BED in the second stage and the cumulative BED1 and BED2 were estimated at 77.63, 58.35 and 115.34 Gy, respectively. Studies reported on dose interval. The results of a random effects model showed that the pooled interval was estimated at 13.86 months. The meta-analysis revealed that using appropriate BED1 and/or BED2 in a safe interval between the first and second phases of treatment can have an influential role in preventing or reducing the effects of myelopathy and regional control pain in spinal reirradiation.

Stereotactic body radiation therapy to the spine: contouring the cauda equina instead of the spinal cord is more practical as the organ at risk

Background

Stereotactic body radiotherapy (SBRT) is recognized as a curative treatment for oligometastasis. The spinal cord becomes the cauda equina at the lumbar level, and the nerves are located dorsally. Recently, a consensus has been reached that the cauda equina should be contoured as an organ at risk (OAR). Here, we examined the separate contouring benefits for the spinal canal versus the cauda equina only as the OAR.

Materials and methods

A medical physicist designed a simulation plan for 10 patients with isolated lumbar metastasis. The OAR was set with three contours: the whole spinal canal, cauda equina only, and cauda equina with bilateral nerve roots. The prescribed dose for the planning target volume (PTV) was 30 Gy/3 fx.

Results

For the constrained QAR doses, D90 and D95 were statistically significant due to the different OAR contouring. The maximum dose (Dmax) was increased to the spinal canal when the cauda equina max was set to ≤ 20 Gy, but dose hotspots were observed in most cases in the medullary area. The Dmax and PTV coverage were negatively correlated for the cauda equina and the spinal canal if Dmax was set to ≤ 20 Gy for both.

Conclusions

A portion of the spinal fluid is also included when the spinal canal is set as the OAR. Thus, the PTV coverage rate will be poor if the tumor is in contact with the spinal canal. However, the PTV coverage rate increases if only the cauda equina is set as the OAR.

Beyond the Knife in Renal Cell Carcinoma: A Systematic Review-To Ablate or Not to Ablate?

Intensified systemic therapy in metastatic renal cell carcinoma (mRCC) has led to improved patient outcomes. Patients commonly require local control of one or a few metastases. The aim was to evaluate metastasis-directed ablative therapies in extracranial mRCC. Two databases and one registry were searched, using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) approach, for all prospective and matched-pair case-control mRCC studies of radiofrequency ablation (RFA), cryotherapy, microwave ablation (MWA), and stereotactic body radiotherapy (SBRT). Eighteen studies were identified. Fourteen investigated SBRT in 424 patients. Four thermal ablation studies were identified: two cryotherapy (56 patients) and two RFA studies (90 patients). The median participant number was 30 (range 12-69). The combined median follow-up was 17.3 months (range 8-52). Four SBRT studies reported local control (LC) at 12 months, median 84.4% (range 82.5-93). Seven studies (six SBRT and one cryotherapy) reported an LC rate of median 87% (79-100%). Median overall survival (OS) was reported in eight studies (five SBRT, two cryotherapy, and one RFA) with a median of 22.7 months (range 6.7-not reached). Median progression-free survival was reported in seven studies (five SBRT, one cryotherapy, and one RFA); the median was 9.3 months (range 3.0-22.7 months). Grade ≥ 3 toxicity ranged from 1.7% to 10%. SBRT has excellent local control outcomes and acceptable toxicity. Only four eligible thermal ablative studies were identified and could not be compared with SBRT. Translationally rich definitive studies are warranted.

Stereotactic Radiosurgery vs Conventional Radiotherapy for Localized Vertebral Metastases of the Spine: Phase 3 Results of NRG Oncology/RTOG 0631 Randomized Clinical Trial

Importance

Spine metastasis can be treated with high-dose radiation therapy with advanced delivery technology for long-term tumor and pain control.

Objective

To assess whether patient-reported pain relief was improved with stereotactic radiosurgery (SRS) as compared with conventional external beam radiotherapy (cEBRT) for patients with 1 to 3 sites of vertebral metastases.

Design, Setting, and Participants

In this randomized clinical trial, patients with 1 to 3 vertebral metastases were randomized 2:1 to the SRS or cEBRT groups. This NRG 0631 phase 3 study was performed as multi-institutional enrollment within NRG Oncology. Eligibility criteria included the following: (1) solitary vertebral metastasis, (2) 2 contiguous vertebral levels involved, or (3) maximum of 3 separate sites. Each site may involve up to 2 contiguous vertebral bodies. A total of 353 patients enrolled in the trial, and 339 patients were analyzed. This analysis includes data extracted on March 9, 2020.

Interventions

Patients randomized to the SRS group were treated with a single dose of 16 or 18 Gy (to convert to rad, multiply by 100) given to the involved vertebral level(s) only, not including any additional spine levels. Patients assigned to cEBRT were treated with 8 Gy given to the involved vertebra plus 1 additional vertebra above and below.

Main Outcomes and Measures

The primary end point was patient-reported pain response defined as at least a 3-point improvement on the Numerical Rating Pain Scale (NRPS) without worsening in pain at the secondary site(s) or the use of pain medication. Secondary end points included treatment-related toxic effects, quality of life, and long-term effects on vertebral bone and spinal cord.

Results

A total of 339 patients (mean [SD] age of SRS group vs cEBRT group, respectively, 61.9 [13.1] years vs 63.7 [11.9] years; 114 [54.5%] male in SRS group vs 70 [53.8%] male in cEBRT group) were analyzed. The baseline mean (SD) pain score at the index vertebra was 6.06 (2.61) in the SRS group and 5.88 (2.41) in the cEBRT group. The primary end point of pain response at 3 months favored cEBRT (41.3% for SRS vs 60.5% for cEBRT; difference, -19 percentage points; 95% CI, -32.9 to -5.5; 1-sided P = .99; 2-sided P = .01). Zubrod score (a measure of performance status ranging from 0 to 4, with 0 being fully functional and asymptomatic, and 4 being bedridden) was the significant factor influencing pain response. There were no differences in the proportion of acute or late adverse effects. Vertebral compression fracture at 24 months was 19.5% with SRS and 21.6% with cEBRT (P = .59). There were no spinal cord complications reported at 24 months.

Conclusions and Relevance

In this randomized clinical trial, superiority of SRS for the primary end point of patient-reported pain response at 3 months was not found, and there were no spinal cord complications at 2 years after SRS. This finding may inform further investigation of using spine radiosurgery in the setting of oligometastases, where durability of cancer control is essential.

Trial Registration

ClinicalTrials.gov Identifier: NCT00922974.

Stereotactic body radiotherapy for spine metastases: a review of 24 Gy in 2 daily fractions

PURPOSE

Stereotactic body radiotherapy (SBRT) has proven to be a highly effective treatment for selected patients with spinal metastases. Randomized evidence shows improvements in complete pain response rates and local control with lower retreatment rates favoring SBRT, compared to conventional external beam radiotherapy (cEBRT). While there are several reported dose-fractionation schemes for spine SBRT, 24 Gy in 2 fractions has emerged with Level 1 evidence providing an excellent balance between minimizing treatment toxicity while respecting patient convenience and financial strain.

METHODS

We provide an overview of the 24 Gy in 2 SBRT fraction regimen for spine metastases, which was developed at the University of Toronto and tested in an international Phase 2/3 randomized controlled trial.

RESULTS

The literature summarizing global experience with 24 Gy in 2 SBRT fractions suggests 1-year local control rates ranging from 83-93.9%, and 1-year rates of vertebral compression fracture ranging from 5.4-22%. Reirradiation of spine metastases that failed prior cEBRT is also feasible with 24 Gy in 2 fractions, and 1-year local control rates range from 72-86%. Post-operative spine SBRT data are limited but do support the use of 24 Gy in 2 fractions with reported 1-year local control rates ranging from 70-84%. Typically, the rates of plexopathy, radiculopathy and myositis are under 5% in those series reporting mature follow up, with no cases of radiation myelopathy (RM) reported in the de novo setting when the spinal cord avoidance structure is limited to 17 Gy in 2 fractions. However, re-irradiation RM has been observed following 2 fraction SBRT. More recently, 2-fraction dose escalation with 28 Gy, with a higher dose constraint to the critical neural tissues, has been reported suggesting improved rates of local control. This regimen may be important in those patients with radioresistant histologies, high grade epidural disease, and/or paraspinal disease.

CONCLUSION

The dose-fractionation of 24 Gy in 2 fractions is well-supported by published literature and is an ideal starting point for centers looking to establish a spine SBRT program.

Spinal Cord Delineation Based on Computed Tomography Myelogram Versus T2 Magnetic Resonance Imaging in Spinal Stereotactic Body Radiation Therapy

Purpose

Spinal cord delineation is critical to the delivery of stereotactic body radiation therapy (SBRT). Although underestimating the spinal cord can lead to irreversible myelopathy, overestimating the spinal cord may compromise the planning target volume coverage. We compare spinal cord contours based on computed tomography (CT) simulation with a myelogram to spinal cord contours based on fused axial T2 magnetic resonance imaging (MRI).

Methods and Materials

Eight patients with 9 spinal metastases treated with spinal SBRT were contoured by 8 radiation oncologists, neurosurgeons, and physicists, with spinal cord definition based on (1) fused axial T2 MRI and (2) CT-myelogram simulation images, yielding 72 sets of spinal cord contours. The spinal cord volume was contoured at the target vertebral body volume based on both images. The mixed-effect model assessed comparisons of T2 MRI- to myelogram-defined spinal cord in centroid deviations (deviations in the center point of the cord) through the vertebral body target volume, spinal cord volumes, and maximum doses (0.035 cc point) to the spinal cord applying the patient's SBRT treatment plan, in addition to in-between and within-subject variabilities.

Results

The estimate for the fixed effect from the mixed model showed that the mean difference between 72 CT volumes and 72 MRI volumes was 0.06 cc and was not statistically significant (95% confidence interval, -0.034, 0.153; P = .1832). The mixed model showed that the mean dose at 0.035 cc for CT-defined spinal cord contours was 1.24 Gy lower than that of MRI-defined spinal cord contours and was statistically significant (95% confidence interval, -2.292, -0.180; P = .0271). Also, the mixed model indicated no statistical significance for deviations in any of the axes between MRI-defined spinal cord contours and CT-defined spinal cord contours.

Conclusions

CT myelogram may not be required when MRI imaging is feasible, although uncertainty at the cord-to-treatment volume interface may result in overcontouring and hence higher estimated cord dose-maximums with axial T2 MRI-based cord definition.

Early Detection of Leptomeningeal Metastases Among Patients Undergoing Spinal Stereotactic Radiosurgery

Purpose

The management of patients with advanced solid malignancies increasingly uses stereotactic body radiation therapy (SBRT). Advanced cancer patients are at risk for developing leptomeningeal metastasis (LM), a fatal complication of metastatic cancer. Cerebrospinal fluid (CSF) is routinely collected during computed tomography (CT) myelography for spinal SBRT planning, offering an opportunity for early LM detection by CSF cytology in the absence of radiographic LM or LM symptoms (subclinical LM). This study tested the hypothesis that early detection of tumor cells in CSF in patients undergoing spine SBRT portends a similarly poor prognosis compared with clinically overt LM.

Methods and Materials

We retrospectively analyzed clinical records for 495 patients with metastatic solid tumors who underwent CT myelography for spinal SBRT planning at a single institution from 2014 to 2019.

Results

Among patients planned for SBRT, 51 (10.3%) developed LM. Eight patients (1.6%) had subclinical LM. Median survival with LM was similar between patients with subclinical versus clinically evident LM (3.6 vs 3.0 months, P = .30). Patients harboring both parenchymal brain metastases and LM (29/51) demonstrated shorter survival than those with LM alone (2.4 vs 7.1 months, P = .02).

Conclusions

LM remains a fatal complication of metastatic cancer. Subclinical LM detected by CSF cytology in spine SBRT patients has a similarly poor prognosis compared with standardly detected LM and warrants consideration of central nervous system-directed therapies. As aggressive local therapies are increasingly used for metastatic patients, more sensitive CSF evaluation may further identify patients with subclinical LM and should be evaluated prospectively.

Hypofractionation and SABR: 25 years of evolution in medical physics and a glimpse of the future

As we were invited to write an article for celebrating the 50^th Anniversary of Medical Physics journal, on something historically significant, commemorative, and exciting happening in the past decades, the first idea came to our mind is the fascinating radiotherapy paradigm shift from conventional fractionation to hypofractionation and stereotactic ablative radiotherapy (SABR). It is historically and clinically significant since as we all know this RT treatment revolution not only reduces treatment duration for patients, but also improves tumor control and cancer treatment outcomes. It is also commemorative and exciting for us medical physicists since the technology development in medical physics has been the main driver for the success of this treatment regimen which requires high precision and accuracy throughout the entire treatment planning and delivery. This article provides an overview of the technological development and clinical trials evolvement in the past 25 years for hypofractionation and SABR, with an outlook to the future improvement.

Could conventionally fractionated radiation therapy coupled with stereotactic body radiation therapy improve local control in bone oligometastases?

PURPOSE

To describe clinical outcomes of stereotactic body radiation therapy (SBRT) applied alone or as a boost after a conventionally fractionated radiation therapy (CFRT) for the treatment of bone oligometastases.

MATERIAL AND METHODS

This retrospective cohort study included patients treated with SBRT from January 2007 to December 2015 in the Institut de cancérologie de Lorraine in France. The inclusion criteria involved adults treated with SBRT for one to three bone metastases from a histological proven solid tumor and a primary tumor treated, an Eastern Cooperative Oncology Group (ECOG) score inferior or equal to 2. Local control (LC), overall survival (OS), progression free survival (PFS), bone progression incidence (BPI), skeletal related events free survival (SRE-FS), toxicity and pain response were evaluated.

RESULTS

Forty-six patients and 52 bone metastases were treated. Twenty-three metastases (44.2%) received SBRT alone mainly for non-spine metastases and 29 (55.8%) a combination of CFRT and SBRT mainly for spine metastases. The median follow-up time was 22months (range: 4-89months). Five local failures (9.6%) were observed and the cumulative incidences of local recurrence at 1 and 2years respectively were 4.4% and 8% with a median time of local recurrence of 17months (range: 4-36months). The one- and two-years OS were 90.8% and 87.4%. Visceral metastasis (HR: 3.40, 95% confidence interval [1.10-10.50]) and a time from primary diagnosis (TPD)>30months (HR: 0.22 [0.06-0.82]) were independent prognostic factors of OS. The 1 and 2years PFS were 66.8% and 30.9% with a median PFS time of 18months [13-24]. The one- and two-years BPI were 27.7% and 55.3%. In multivariate analysis, unfavorable histology was associated with worse BPI (HR: 3.19 [1.32-7.76]). The SRE-FS was 93.3% and 78.5% % at 1 and 2years. The overall response rate for pain was 75% in the evaluable patients (9/12). No grade≥3 toxicity nor especially no radiation induced myelopathy (RIM), two patients developed asymptomatic vertebral compression fractures.

CONCLUSION

The sole use of SBRT or its association with CFRT is an efficient and well-tolerated treatment that allows high LC for bone oligometastases.

Volumetric Intensity-Modulated Arc Stereotactic Radiosurgery Boost in Oligometastatic Patients with Spine Metastases: a Dose-escalation Study

AIMS

To report the final results of a dose-escalation study of volumetric intensity-modulated arc stereotactic radiosurgery (VMAT-SRS) boost after three-dimensional conformal radiation therapy in patients with spine metastases.

MATERIALS AND METHODS

Oligometastatic cancer patients bearing up to five synchronous metastases (visceral or bone, including vertebral ones) and candidates for surgery or radiosurgery were considered for inclusion. 25 Gy was delivered in 10 daily fractions (2 weeks) to the metastatic lesion, affected vertebrae and adjacent ones (one cranial and one caudal vertebra). Sequentially, the dose to spinal metastases was progressively increased (8 Gy, 10 Gy, 12 Gy) in the patient cohorts. Dose-limiting toxicities were defined as any treatment-related non-hematologic acute adverse effects rated as grade ≥3 or any acute haematological toxicity rated as ≥ 4 by the Radiation Therapy Oncology Group scale.

RESULTS

Fifty-two lesions accounting for 40 consecutive patients (male/female: 29/11; median age: 71 years; range 40-85) were treated from April 2011 to September 2020. Most patients had a primary prostate (65.0%) or breast cancer (22.5%). Thirty-two patients received 8 Gy VMAT-SRS boost (total BED _α/β10: 45.6 Gy), 14 patients received 10 Gy (total BED _α/β10: 51.2 Gy) and six patients received 12 Gy (total BED _α/β10: 57.6 Gy). The median follow-up time was over 70 months (range 2-240 months). No acute toxicities > grade 2 and no late toxicities > grade 1 were recorded. The overall response rate based on computed tomography/positron emission tomography-computed tomography/magnetic resonance was 78.8%. The 24-month actuarial local control, distant metastases-free survival and overall survival rates were 88.5%, 27.1% and 90.3%, respectively.

CONCLUSION

A 12 Gy spine metastasis SRS boost following 25 Gy to the affected and adjacent vertebrae was feasible with an excellent local control rate and toxicity profile.

Feasibility, safety, and efficacy of circumferential spine stereotactic body radiotherapy

Background

With advances in systemic therapy translating to improved survival in metastatic malignancies, spine metastases have become an increasingly common source of morbidity. Achieving durable local control (LC) for patients with circumferential epidural disease can be particularly challenging. Circumferential stereotactic body radiotherapy (SBRT) may offer improved LC for circumferential vertebral and/or epidural metastatic spinal disease, but prospective (and retrospective) data are extremely limited. We sought to evaluate the feasibility, toxicity, and cancer control outcomes with this novel approach to circumferential spinal disease.

Methods

We retrospectively identified all circumferential SBRT courses delivered between 2013 and 2019 at a tertiary care institution for post-operative or intact spine metastases. Radiotherapy was delivered to 14-27.5 Gy in one to five fractions. Feasibility was assessed by determining the proportion of plans for which ≥95% planning target volume (PTV) was coverable by ≥95% prescription dose. The primary endpoint was 1-year LC. Factors associated with increased likelihood of local failure (LF) were explored. Acute and chronic toxicity were assessed. Detailed dosimetric data were collected.

Results

Fifty-eight patients receiving 64 circumferential SBRT courses were identified (median age 61, KPS ≥70, 57% men). With a median follow-up of 15 months, the 12-month local control was 85% (eight events). Five and three recurrences were in the epidural space and bone, respectively. On multivariate analysis, increased PTV and uncontrolled systemic disease were significantly associated with an increased likelihood of LF; ≥95% PTV was covered by ≥95% prescription dose in 94% of the cases. The rate of new or progressive vertebral compression fracture was 8%. There were no myelitis events or any grade 3+ acute or late toxicities.

Conclusions

For patients with circumferential disease, circumferential spine SBRT is feasible and may offer excellent LC without significant toxicity. A prospective evaluation of this approach is warranted.

Recommendations for radiation therapy in oligometastatic prostate cancer: An ESTRO-ACROP Delphi consensus

BACKGROUND AND PURPOSE

Oligometastatic prostate cancer is a new and emerging treatment field with only few prospective randomized studies published so far. Despite the lack of strong level I evidence, metastasis-directed therapies (MDT) are widely used in clinical practice, mainly based on retrospective and small phase 2 studies and with a large difference across centers. Pending results of ongoing prospective randomized trials, there is a clear need for more consistent treatment indications and radiotherapy practices.

MATERIAL AND METHODS

A European Society for Radiotherapy and Oncology (ESTRO) Guidelines Committee consisting of radiation oncologists' experts in prostate cancer was asked to answer a dedicated questionnaire, including 41 questions on the main controversial issues with regard to oligometastatic prostate cancer.

RESULTS

The panel achieved consensus on patient selection and routine use of prostate-specific membrane antigen positron emission tomography (PSMA PET) imaging as preferred staging and restaging imaging. MDT strategies are recommended in the de novo oligometastatic, oligorecurrent and oligoprogressive disease setting for nodal, bone and visceral metastases. Radiation therapy doses, volumes and techniques were discussed and commented.

CONCLUSION

These recommendations have the purpose of providing standardization and consensus to optimize the radiotherapy treatment of oligometastatic prostate cancer until mature results of randomized trials are available.

A quantitative and comparative evaluation of stereotactic spine radiosurgery local control: proposing a consistent measurement methodology

OBJECTIVE

Stereotactic body radiotherapy (SBRT) is a precise and conformal treatment modality used in the management of metastatic spine tumors. Multiple studies have demonstrated its safety and efficacy for pain and tumor control. However, no uniform quantitative imaging methodology exists to evaluate response to treatment in these patients. This study presents radiographic local control rates post-SBRT, systematically compares measurements acquired according to WHO and Response Evaluation Criteria in Solid Tumors (RECIST) criteria, and explores the relationship to patient outcome.

METHODS

The authors performed a retrospective review of prospectively obtained data from a cohort of 59 consecutive patients (81 metastatic isocenters) treated with SBRT and followed with serial MRI scans. Measurements were performed by a neuroradiologist blinded to the patients’ clinical course. Local control status was determined according to both WHO and RECIST measurements, and agreement between the measuring methodologies was calculated and reported.

RESULTS

Eighty-one isocenters (111 vertebral bodies) were treated with SBRT. The mean treatment dose was 13.96 Gy and the median follow-up duration was 10.8 months, during which 408 MRI scans were evaluated with both WHO and RECIST criteria for each scan point. Imaging demonstrated a mean unidimensional size decrease of 0.2 cm (p = 0.14) and a mean area size decrease of 0.99 cm2 (p = 0.03). Although 88% of the case classifications were concordant and the agreement was significant, WHO criteria were found to be more sensitive to tumor size change. The local control rates according to WHO and RECIST were 95% and 98%, respectively.

CONCLUSIONS

Although WHO volumetric measurements are admittedly superior for tumor size measurement, RECIST is simpler, reproducible, and for the first time is shown here to be comparable to WHO criteria. Thus, the application of RECIST methodology appears to be a suitable standard for evaluating post-SBRT treatment response. Moreover, using comprehensive and consistent measuring approaches, this study substantiates the efficacy of SBRT in the treatment of spine metastases.

Efficacy and safety of stereotactic body radiotherapy for painful bone metastases: Evidence from randomized controlled trials

BACKGROUND

Pain relief is one of the main objectives of radiotherapy for cancer patients with bone metastases. Stereotactic body radiotherapy (SBRT) enables precise delivery of a higher dosage to the target area. Several trials have reported comparisons between SBRT and conventional radiotherapy (cRT) in patients with painful bone metastasis. However, the results of those investigations were inconsistent, and no systematic review or meta-analysis has been done till now.

METHODS

We systematically searched MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials (CENTRAL), and Clinicaltrials.gov up to May 1, 2022 for relevant studies. Patients with painful bone metastasis who received SBRT or cRT were included. The primary outcome was the patients' pain response rate at three months. The secondary outcomes included the rate of pain responders at one month and six months, oral morphine equivalent dose (OMED) use, and any adverse events. STATA software 12.0 was used for the statistical analysis.

RESULTS

We collected 533 patients' data from 4 randomized controlled trials (RCTs), there was a significant difference of pain response rate at 3 months between two groups (RR = 1.41, 95% CI: 1.12-1.77, I2 = 0.0%, P = 0.003). However, no significant difference was found in pain response rate at 1 month (RR = 1.19, 95% CI: 0.91-1.54, I2 = 31.5%, P = 0.201) and 6 months (RR = 1.25, 95% CI: 0.93-1.69, I2 = 0.0%, P = 0.140). OMED consumption was not significantly different in patients treated with SBRT compared with control group (WMD = -1.11, 95% CI: -17.51-15.28, I2 = 0.0%, P = 0.894). For safety outcome, no statistical difference was found between SBRT and cRT (RR = 0.72, 95% CI: 0.46-1.14, I2=20.1%, P = 0.162).

CONCLUSION

This study shows that for painful bone metastases, patients with SBRT experienced better pain relief 3 months after radiation than patients with cRT, and SBRT did not increase the incidence of adverse events.

SYSTEMATIC REVIEW REGISTRATION

https://inplasy.com/inplasy-2022-6-0099/, identifier INPLASY202260099.

Independent predictors of vertebral compression fracture following radiation for metastatic spine disease

OBJECTIVE

The goal of this study was to determine independent risk factors for vertebral compression fracture (VCF) following radiation for metastatic spine disease, including low bone mineral density as estimated by Hounsfield units (HU).

METHODS

A retrospective chart review identified patients with a single vertebral column metastasis treated with radiation therapy, a pretreatment CT scan, and a follow-up CT scan at least 6 weeks after treatment. Patients with primary spine tumors, preradiation vertebroplasty, preradiation spine surgery, prior radiation to the treatment field, and proton beam treatment modality were excluded. The HU were measured in the vertebral bodies at the level superior to the metastasis, within the tumor and medullary bone of the metastatic level, and at the level inferior to the metastasis. Variables collected included basic demographics, Spine Instability Neoplastic Score (SINS), presenting symptoms, bone density treatment, primary tumor pathology, Weinstein-Boriani-Biagini (WBB) classification, Enneking stage, radiation treatment details, chemotherapy regimen, and prophylactic vertebroplasty.

RESULTS

One hundred patients with an average age of 63 years and average follow-up of 18 months with radiation treatment dates ranging from 2017 to 2020 were included. Fifty-nine patients were treated with external-beam radiation therapy, with a median total dose of 20 Gy (range 8-40 Gy). Forty-one patients were treated with stereotactic body radiation therapy, with a median total dose of 24 Gy (range 18-39 Gy). The most common primary pathologies included lung (n = 22), prostate (n = 21), and breast (n = 14). Multivariable logistic regression analysis (area under the curve 0.89) demonstrated pretreatment HU (p < 0.01), SINS (p = 0.02), involvement of ≥ 3 WBB sectors (p < 0.01), primary pathology other than prostate (p = 0.04), and ongoing chemotherapy treatment (p = 0.04) to be independent predictors of postradiation VCF. Patients with pretreatment HU < 145 (n = 32), 145-220 (n = 31), and > 220 (n = 37) had a fracture rate of 59%, 39%, and 11%, respectively. An HU cutoff of 157 was found to maximize sensitivity (71%) and specificity (75%) in predicting postradiation VCF.

CONCLUSIONS

Low preradiation HU, higher SINS, involvement of ≥ 3 WBB sectors, ongoing chemotherapy, and nonprostate primary pathology were independent predictors of postradiation VCF in patients with metastatic spine disease. Low bone mineral density, as estimated by HU, is a novel and potentially modifiable risk factor for VCF.

Multidisciplinary management of spinal metastases: what the radiologist needs to know

The modern management of spinal metastases requires a multidisciplinary approach that includes radiation oncologists, surgeons, medical oncologists, and diagnostic and interventional radiologists. The diagnostic radiologist can play an important role in the multidisciplinary team and help guide assessment of disease and selection of appropriate therapy. The assessment of spine metastases is best performed on MRI, but imaging from other modalities is often needed. We provide a review of the clinical and imaging features that are needed by the multidisciplinary team caring for patients with spine metastases and stress the importance of the spine radiologist taking responsibility for synthesizing imaging features across multiple modalities to provide a report that advances patient care.

Dosimetric analysis of MR-LINAC treatment plans for salvage spine SBRT re-irradiation

PURPOSE

We investigated the feasibility of thoracic spine stereotactic body radiotherapy (SBRT) using the Elekta Unity magnetic resonance-guided linear accelerator (MRL) in patients who received prior radiotherapy. We hypothesized that Monaco treatment plans can improve the gross tumor volume minimum dose (GTVmin) with spinal cord preservation and maintain consistent plan quality during daily adaptation.

METHODS

Pinnacle clinical plans for 10 patients who underwent thoracic spine SBRT (after prior radiotherapy) were regenerated in the Monaco treatment planning system for the Elekta Unity MRL using 9 and 13 intensity-modulated radiotherapy (IMRT) beams. Monaco adapt-to-position (ATP) and adapt-to-shape (ATS) workflow plans were generated using magnetic resonance imaging with a simulated daily positional setup deviation, and these adaptive plans were compared with Monaco reference plans. Plan quality measures included target coverage, Paddick conformity index, gradient index, homogeneity index, spinal cord D_0.01cc , esophagus D_0.01cc , lung V10, and skin D_0.01cc .

RESULTS

GTVmin values from the Monaco 9-beam and 13-beam plans were significantly higher than those from Pinnacle plans (p < 0.01) with similar spinal cord dose. Spinal cord D_0.01cc , esophagus D_0.01cc , and lung V10 did not statistically differ among the three plans. The electron-return effect did not induce remarkable dose effects around the lungs or skin. While in the ATP workflow, a large increase in GTVmin was observed at the cost of a 10%-50% increase in spinal cord D_0.01cc , in the ATS workflow, the spinal cord dose increase was maintained within 3% of the reference plan.

CONCLUSION

These findings show that MRL plans for thoracic spine SBRT are safe and feasible, allowing tumor dose escalation with spinal cord preservation and consistent daily plan adaptation using the ATS workflow. Careful plan review of hot spots and lung dose is necessary for safe MRL-based treatment.

Spine Stereotactic Body Radiotherapy to Three or More Contiguous Vertebral Levels

Background

With survival improving in many metastatic malignancies, spine metastases have increasingly become a source of significant morbidity; achieving durable local control (LC) is critical. Stereotactic body radiotherapy (SBRT) may offer improved LC and/or symptom palliation. However, due to setup concerns, SBRT is infrequently offered to patients with ≥3 contiguous involved levels. Because data are limited, we sought to evaluate the feasibility, toxicity, and cancer control outcomes of spine SBRT delivered to ≥3 contiguous levels.

Methods

We retrospectively identified all SBRT courses delivered between 2013 and 2019 at a tertiary care institution for postoperative or intact spine metastases. Radiotherapy was delivered to 14-35 Gy in 1-5 fractions. Patients were stratified by whether they received SBRT to 1-2 or ≥3 contiguous levels. The primary endpoint was 1-year LC and was compared between groups. Factors associated with increased likelihood of local failure (LF) were explored. Acute and chronic toxicity was assessed. In-depth dosimetric data were collected.

Results

Overall, 165 patients with 194 SBRT courses were identified [54% were men, median age was 61 years, 93% had Karnofsky Performance Status (KPS) ≥70, and median follow-up was 15 months]. One hundred thirteen patients (68%) received treatment to 1-2 and 52 to 3-7 (32%) levels. The 1-year LC was 88% (89% for 1-2 levels vs. 84% for ≥3 levels, p = 0.747). On multivariate analysis, uncontrolled systemic disease was associated with inferior LC for patients with ≥3 treated levels. No other demographic, disease, treatment, or dosimetric variables achieved significance. Rates of new/progressive fracture were equivalent (8% vs. 9.5%, p = 0.839). There were no radiation-induced myelopathy or grade 3+ acute or late toxicities in either group. Coverage of ≥95% of the planning target volume with ≥95% prescription dose was similar between groups (96% 1-2 levels vs. 89% ≥3 levels, p = 0.078).

Conclusions

For patients with ≥3 contiguous involved levels, spine SBRT is feasible and may offer excellent LC without significant toxicity. Prospective evaluation is warranted.

A randomized controlled trial for evaluating pain response in patients with spinal metastases following local versus whole vertebral radiotherapy: study protocol for phase II clinical trial

BACKGROUND

Patients with bone metastasis often experience severe pain that is difficult to control and seriously affects quality of life. Radiotherapy is an effective way to relieve pain in these patients. Currently, there is no standard recommended range of radiotherapy targets for vertebral metastasis. The effect of radiotherapy on pain relief varies among patients, and some patients with metastases have serious side effects.

METHODS

This study aims to verify whether reducing the radiotherapy range for vertebral metastases can achieve the same effect as whole vertebral radiotherapy while minimizing side effects. Sixty-six patients with pain caused by vertebral metastasis were randomly divided into two groups. The study group is receiving partial vertebrae body radiotherapy at the regions of abnormal signal, suspected invasion, and adjacent subclinical focus of vertebral metastasis, and the control group is receiving the same dose of radiotherapy on whole vertebrae body where metastasis occurred. After radiotherapy, along-term follow-up of patients will determine pain relief and side effects.

DISCUSSION

The expected results of this study are that local irradiation of vertebral metastases can achieve a palliative effect of pain control not less than total vertebral irradiation with fewer side effects.

TRIAL REGISTRATION

This study was registered in the Chinese Clinical Trial Registry (No: ChiCTR1900023401 ).

Comparing Outcomes of Oligometastases Treated with Hypofractionated Image-Guided Radiotherapy (HIGRT) with a Simultaneous Integrated Boost (SIB) Technique versus Metastasis Alone: A Multi-Institutional Analysis

Simple Summary

Hypofractionated image-guided radiotherapy (HIGRT) is a common method in which high doses of radiation are delivered to treat oligometastatic disease. We have previously reported on the clinical outcomes of treating oligometastases with radiation using an elective simultaneous integrated boost technique (SIB), delivering higher doses to known metastases and reduced doses to adjacent bone or nodal basins. Here we compare outcomes of oligometastases receiving radiation targeting metastases alone (MA) versus those treated via an SIB. Both SIB and MA irradiation of oligometastases achieved high rates of tumor metastases control and similar pain control. Further investigation of this technique with prospective trials is warranted.

Abstract

Purpose: We previously reported on the clinical outcomes of treating oligometastases with radiation using an elective simultaneous integrated boost technique (SIB), delivering higher doses to known metastases and reduced doses to adjacent bone or nodal basins. Here we compare outcomes of oligometastases receiving radiation targeting metastases alone (MA) versus those treated via an SIB. Methods: Oligometastatic patients with ≤5 active metastases treated with either SIB or MA radiation at two institutions from 2013 to 2019 were analyzed retrospectively for treatment-related toxicity, pain control, and recurrence patterns. Tumor metastasis control (TMC) was defined as an absence of progression in the high dose planning target volume (PTV). Marginal recurrence (MR) was defined as recurrence outside the elective PTV but within the adjacent bone or nodal basin. Distant recurrence (DR) was defined as any recurrence that is not within the PTV or surrounding bone or nodal basin. The outcome rates were estimated using the Kaplan–Meier method and compared between the two techniques using the log-rank test. Results: 101 patients were treated via an SIB to 90 sites (58% nodal and 42% osseous) and via MA radiation to 46 sites (22% nodal and 78% osseous). The median follow-up among surviving patients was 24.6 months (range 1.4–71.0). Of the patients treated to MA, the doses ranged from 18 Gy in one fraction (22%) to 50 Gy in 10 fractions (50%). Most patients treated with an SIB received 50 Gy to the treated metastases and 30 Gy to the elective PTV in 10 fractions (88%). No acute grade ≥3 toxicities occurred in either cohort. Late grade ≥3 toxicity occurred in 3 SIB patients (vocal cord paralysis and two vertebral body compression), all related to the high dose PTV and not the elective volume. There was similar crude pain relief between cohorts. The MR-free survival rate at 2 years was 87% (95% CI: 70%, 95%) in the MA group and 98% (95% CI: 87%, 99%) in the SIB group (p = 0.07). The crude TMC was 89% (41/46) in the MA group and 94% (85/90) in the SIB group. There were no significant differences in DR-free survival (65% (95% CI: 55–74%; p = 0.24)), disease-free survival (60% (95% CI: 40–75%; p = 0.40)), or overall survival (88% (95% CI: 73–95%; p = 0.26)), between the MA and SIB cohorts. Conclusion: Both SIB and MA irradiation of oligometastases achieved high rates of TMC and similar pain control, with a trend towards improved MR-free survival for oligometastases treated with an SIB. Further investigation of this technique with prospective trials is warranted.

Utility of expanded anterior column resection versus decompression-alone for local control in the management of carcinomatous vertebral column metastases undergoing adjuvant stereotactic radiotherapy

BACKGROUND CONTEXT

With improvements in adjuvant radiotherapy and minimally invasive surgical techniques, separation surgery has become the default surgical intervention for spine metastases at many centers. However, it is unclear if there is clinical benefit from anterior column resection in addition to simple epidural debulking prior to stereotactic body radiotherapy (SBRT).

PURPOSE

To examine the effect of anterior column debulking versus epidural disease resection alone in the local control of metastases to the bony spine.

STUDY DESIGN

Retrospective cohort study.

PATIENT SAMPLE

Ninety-seven patients who underwent open surgery followed by SBRT for spinal metastases at a single comprehensive cancer center.

OUTCOME MEASURES

Local tumor recurrence following surgery and SBRT.

METHODS

Data were collected regarding radiation dose, cancer histology, extent of anterior column resection, and recurrence. Tumor involvement was categorized using the International Spine Radiosurgery Consortium guidelines. Univariable analyses were conducted to determine predictors of local recurrence and time to local recurrence.

RESULTS

Among the 97 included patients, mean age was 60.5±11.4 years and 51% of patients were male. The most common primary tumor types were lung (20.6%), breast (17.5%), kidney (13.4%) and prostate (12.4%). Recurrence was seen in 17 patients (17.5%) and local control rates were: 85.5% (1-year), 81.1% (2-year), and 54.9% (5-year). Overall predictors of local recurrence were tumor pathology (p<.01; renal cell carcinoma and colorectal adenocarcinoma associated with poorest PFS) and undergoing anterior column debulking versus epidural decompression-alone (p=.03). Only tumor pathology predicted time to local recurrence (p<.01), though inspection of Kaplan-Meier functions showed superior long-term local control in patients with radiosensitive tumor pathologies, no previous irradiation of the metastasis, and who underwent anterior column resection versus epidural removal alone. Median time to recurrence was 288 days with 100% of lesions showing anterior column recurrence and recurrence in the epidural space.

CONCLUSIONS

With the increasing shift towards surgery as a neoadjuvant to radiotherapy for patients with spinal column metastases, the role for surgical debulking has become less clear. In the present study, we find that anterior column debulking as opposed to epidural debulking-alone decreases the odds of local recurrence and improves long-term local control.

Stereotactic radiotherapy (SRT) for differentiated thyroid cancer (DTC) oligometastases: an AIRO (Italian association of radiotherapy and clinical oncology) systematic review

PURPOSE

The aim of this systematic review was to examine efficacy of stereotactic radiotherapy (SRT) in patients with oligometastatic thyroid cancer.

MATERIALS AND METHODS

A systematic search was conducted by means of PubMed, Scopus, and Cochrane library.

CLINICALTRIALS

gov was searched for ongoing or recently completed trials, and PROSPERO was searched for ongoing or recently completed systematic reviews. We analyzed only clinical studies as full text carried out on patients with oligometastatic thyroid cancer treated with SRT. Conference papers, surveys, letters, editorials, book chapters, and reviews were excluded. Time of publication was restricted to the years 1990-2021.

RESULTS

The number of evaluated patients was 146 (267 lesions), and the median age was 58 years. The median 1-year local control (LC) was 82% (range 67.0%-97.1%); the median disease-free survival (DFS) was 12 months (range 4-53); the median 1-year overall survival was 72% (range 66.6%-85.0%); the 3-year cancer-specific survival was 75.0%; and the 4-year cancer-specific survival was 37.5%. No grade 3-5 acute toxicity was reported. No late effects were recorded.

CONCLUSIONS

SRT for oligometastases from thyroid cancer as salvage therapy is well tolerated and yields high rates of LC and prolonged DFS.

Evaluation of a proprietary software application for motion monitoring during stereotactic paraspinal treatment

PURPOSE

Stereotactic paraspinal treatment has become increasingly popular due to its favorable clinical outcome. An often-overlooked factor that compromises the effectiveness of such treatment is the patients' involuntary intrafractional motion. This work introduces and validates a proprietary software application that quantifies such motion for accurate patient monitoring during treatment.

METHODS

The software uses a separate full-trajectory cone-beam computed tomography (CBCT) after daily patient setup to establish reference projections. Once treatment starts, the software grabs the intrafraction motion review (IMR) image acquired by TrueBeam via the Varian iTools Capture software and compares it against the corresponding reference projection to instantly determine the 2D shifts of the vertebrae being monitored using the classical downhill simplex optimization method. To evaluate its performance, an anthropomorphic phantom was shifted 0, 0.6, 1.2, 1.8, 2.4, 3.0, and 5 mm in three orthogonal directions, immediately after the full-trajectory CBCT but prior to treatment. Depending on the scenario of shift, a nine-field fixed gantry intensity-modulated radiation therapy (IMRT) plan and/or a four partial-posterior-arcs volume-modulated radiation therapy (VMAT) plan were delivered. For the IMRT plan, three IMR images were acquired sequentially every 200 monitor units (MU) at each treatment angle. For the VMAT plan, one IMR image was acquired every 15° of each arc. For each IMR image, the software-reported 2D shift was compared with the ground truth. Certain tests were repeated with 1°, 2°, and 3° of rotation, pitch, and roll, respectively. Some of these tests were also repeated independently on separate days.

RESULTS

Based on the group of tests that involved only the IMRT delivery, the maximum standard deviation of the software-reported shifts for each set of three IMR images was 0.16 mm, with 95th percentile at 0.02 mm. For translational shift, the maximum registration error was 0.44 mm, with 95th percentile at 0.23 mm. Left unaccounted for, rotation and pitch degraded the registration accuracy mainly in the longitudinal direction, while roll degraded it mainly in the lateral direction. The degradation of registration accuracy is positively related to the degree of rotation, pitch, and roll. The maximum registration errors under 3° rotation, pitch, and roll were 2.97, 1.44, 2.72 mm, respectively. Based on the group of tests that compared IMRT delivery with VMAT delivery, the registration errors slightly increased as magnitude of shifts increased; however, they were well under the 0.5-mm threshold. No significant differences in registration errors were observed between IMRT and VMAT deliveries. In addition, the variation in registration errors among different days was limited for both IMRT and VMAT deliveries.

CONCLUSIONS

Our proprietary software has high repeatability, both intrafractionally and interfractionally, and high accuracy in registering IMR images with the reference projections for motion monitoring, regardless of the magnitude of shifts or treatment delivery technique. Rotation, pitch, and roll degrade registration accuracy and need to be accounted for in the future work.

The Effect of High-Dose Radiation Therapy on Healthy Vertebral Bone Density

Objective

Increased rates of insufficiency fractures are reported after radiation therapy without well-defined causality. Here, we conduct a cross-sectional study on the density change of a non-lesioned vertebral bone after irradiation relative to a control bone in patients with spinal metastases.

Methods

Patients were identified who received radiation therapy for spinal metastases to a region, including an adjacent vertebra without identifiable malignancy on pre-treatment CT. Every patient had an untreated vertebra of a similar type available as a control. A Hounsfield-density calibration curve was used to measure the vertebral body density before and after treatment. Analysis of covariance was used to model vertebral bone density changes with respect to treatment status. Significance was established as p < 0.05.

Results

We identified 36 patients who fit the study criteria. The irradiated healthy bone received a median dose of 30 Gy. The median biologically effective dose (BED) was 60 Gy (α/β = 3) and 39 Gy (α/β = 10). Median follow-up imaging intervals between pre-treatment and follow-up CT scans was 13.4 months. Levene’s test was used to confirm the equality of error variance assumption of ANCOVA (p = 0.093). The mean change in the density of the irradiated vertebral bone was -3.59% (95% CI = -8.51% - 1.32%, p = 0.149).

Conclusions

We found no significant change in vertebral bone density attributable to radiation treatment. Further work is needed to elucidate if increased fracture rates after radiation are due to factors other than bone density.

Hybrid Therapy (Surgery and Radiosurgery) for the Treatment of Renal Cell Carcinoma Spinal Metastases

BACKGROUND

The management of spinal metastatic renal cell carcinoma (mRCC) is controversial regarding extent of resection and radiation dosing.

OBJECTIVE

To determine outcomes in patients treated with hybrid therapy (separation surgery plus adjuvant stereotactic body radiation therapy [SBRT]) for mRCC.

METHODS

A retrospective study of a prospectively collected cohort of patients undergoing hybrid therapy for mRCC between 2003 and 2017 was performed. SBRT was delivered as high-dose single-fraction, high-dose hypofractionated, or low-dose hypofractionated. Extent of disease, clinical and operative outcomes, and complications data were collected, and associations with overall survival (OS) and progression-free survival were determined.

RESULTS

Ninety patients with mRCC with high-grade epidural spinal cord compression (ESCC grades 2 and 3) were treated. Metastases were widespread, oligometastatic, and solitary in 56%, 33%, and 11% of patients, respectively. SBRT delivered was high-dose single-fraction, high-dose hypofractionated, and low-dose hypofractionated in 24%, 56%, and 20% of patients, respectively. The 1-yr cumulative incidence of major complications was 3.4% (95% confidence interval [CI]: 0.0%-7.2%). The median follow-up was 14.2 mo for the entire cohort and 38.3 mo for survivors. The 1-yr cumulative incidence of progression was 4.6% (95% CI: 0.2%-9.0%), which translates to a local control rate of 95.4% (95% CI: 91.0%-99.8%) 1 yr after surgery. The median OS for the cohort was 14.8 mo.

CONCLUSION

These data support the use of hybrid therapy as a safe and effective strategy for the treatment of renal cell spine metastases.

Re-irradiation of recurrent vertebral metastasis after two previous spinal cord irradiation: A case report

Background

Management of a recurrent vertebral metastasis in a situation of previously irradiated spinal cord is a challenging clinical dilemma.

Case presentation

We report a first case of second retreatment of a spinal metastasis initially irradiated with standard radiotherapy and stereotactic body radiation therapy (SBRT), who subsequently progressed with imaging-confirmed local tumor progression at the same level. After a third course of irradiation with SBRT, a complete response was achieved. After 8 months of follow-up, the patients remain free of local recurrence.

Conclusion

A third course of vertebral irradiation for a recurrent vertebral metastasis failing to two previous irradiations, in this particular case, have shown the feasibility and efficacy of the technique as a salvage treatment option. This approach could be used in a selected group of patient if an adequate dose is delivered to the target while observing critical tissue tolerance limits.

Decompose kV projection using neural network for improved motion tracking in paraspinal SBRT

PURPOSE

 On-treatment kV images have been used in tracking patient motion. One challenge of markerless motion tracking in paraspinal SBRT is the reduced contrast when the X-ray beam needs to pass through a large portion of the patient's body, for example, from the lateral direction. Besides, due to the spine's overlapping with the surrounding moving organs in the X-ray images, auto-registration could lead to potential errors. This work aims to automatically extract the spine component from the conventional 2D X-ray images, to achieve more robust and more accurate motion management.

METHODS

 A ResNet generative adversarial network (ResNetGAN) consisting of one generator and one discriminator was developed to learn the mapping between 2D kV image and the reference spine digitally reconstructed radiograph (DRR). A tailored multi-channel multi-domain loss function was used to improve the quality of the decomposed spine image. The trained model took a 2D kV image as input and learned to generate the spine component of the X-ray image. The training dataset included 1347 2D kV thoracic and lumbar region X-ray images from 20 randomly selected patients, and the corresponding matched reference spine DRR. Another 226 2D kV images from the remaining four patients were used for evaluation. The resulted decomposed spine images and the original X-ray images were registered to the reference spine DRRs, to compare the spine tracking accuracy.

RESULTS

 The decomposed spine image had the mean peak signal-to-noise ratio (PSNR) and structural similarity index measure (SSIM) of 60.08 and 0.99, respectively, indicating the model retained and enhanced the spine structure information in the original 2D X-ray image. The decomposed spine image matching with the reference spine DRR had submillimeter accuracy (in mm) with a mean error of 0.13, 0.12, and a maximum of 0.58, 0.49 in the x - and y -directions (in the imager coordinates), respectively. The accuracy improvement is robust in all lateral and anteroposterior X-ray beam angles.

CONCLUSION

 We developed a deep learning-based approach to remove soft tissues in the kV image, leading to more accurate spine tracking in paraspinal SBRT.

International Multi-institutional Patterns of Contouring Practice and Clinical Target Volume Recommendations for Stereotactic Body Radiation Therapy for Non-Spine Bone Metastases

PURPOSE

Despite the increasing use of stereotactic body radiation therapy for non-spine bone metastases (NSBM), there is no established standard for target delineation. The objective of this study was to provide consensus recommendations on clinical target volume (CTV) delineation based on international expert contours.

METHODS AND MATERIALS

Eleven cases of NSBM were contoured by 9 international radiation oncologists. For each case, the gross tumor volume was provided on the simulation computed tomography scans with accompanying magnetic resonance imaging. Participants contoured the CTV and completed a clinical survey. Agreement between CTV contours were analyzed with simultaneous truth and performance level estimation using the kappa coefficient and the Dice similarity coefficient (DSC) and summarized to establish contouring recommendations. A direction-dependent analysis was applied to the consensus contours to quantify margins.

RESULTS

All CTV contours were completed. Six participants used a single-dose level, whereas 3 used a 2-dose level simultaneous integrated boost (SIB) technique. For the SIB cases, the largest volume receiving a stereotactic body radiation therapy (SBRT) dose was used for contour analysis. There was substantial agreement between contours across cases with a mean kappa of 0.72 (mean sensitivity 0.85, mean specificity 0.97). The mean DSC value was 0.77 (range, 0.67-0.87). Consensus CTV contouring recommendations were (1) an intraosseous CTV margin of 5 to 10 mm should be strongly considered within contiguous bone; (2) an extraosseous margin of 5 to 10 mm should be strongly considered where there is soft tissue disease or cortical bone disruption; (3) CTVs should be manually cropped to respect anatomic barriers to spread (eg, peritoneal cavity, pleura, uninvolved joint space and cortical bone).

CONCLUSIONS

CTV contouring recommendations for NSBM-SBRT were established based on analysis of international expert consensus contours with a high level of agreement. These principles may provide guidance to treating physicians and inform future study until prospective clinical data can provide further refinement.