Boron neutron capture therapy delays the decline in neurological function in a mouse model of metastatic spinal tumors.

Metastatic spinal tumors are increasingly prevalent due to advancements in cancer treatment, leading to prolonged survival rates. This rising prevalence highlights the need for developing more effective therapeutic approaches to address this malignancy. Boron neutron capture therapy (BNCT) offers a promising solution by delivering targeted doses to tumors while minimizing damage to normal tissue. In this study, we evaluated the efficacy and safety of BNCT as a potential therapeutic option for spine metastases in mouse models induced by A549 human lung adenocarcinoma cells. The animal models were randomly allocated into three groups: untreated (n = 10), neutron irradiation only (n = 9), and BNCT (n = 10). Each mouse was administered 4-borono-L-phenylalanine (250 mg/kg) intravenously, followed by measurement of boron concentrations 2.5 h later. Overall survival, neurological function of the hindlimb, and any adverse events were assessed post irradiation. The tumor-to-normal spinal cord and blood boron concentration ratios were 3.6 and 2.9, respectively, with no significant difference observed between the normal and compressed spinal cord tissues. The BNCT group exhibited significantly prolonged survival rates compared with the other groups (vs. untreated, p = 0.0015; vs. neutron-only, p = 0.0104, log-rank test). Furthermore, the BNCT group demonstrated preserved neurological function relative to the other groups (vs. untreated, p = 0.0004; vs. neutron-only, p = 0.0051, multivariate analysis of variance). No adverse events were observed post irradiation. These findings indicate that BNCT holds promise as a novel treatment modality for metastatic spinal tumors.

Dose-intensified stereotactic body radiotherapy for painful vertebral metastases: A randomized phase 3 trial.

BACKGROUND: The purpose of this randomised study was to determine whether dose-intensified stereotactic body radiotherapy (SBRT) for painful vertebral metastases results in increased rates of pain improvement compared with conventional external beam radiotherapy (cEBRT) (control) 6 months after treatment. METHODS: This randomized, controlled phase 3 trial was conducted between November 2016 and January 2023, when it was stopped early. Patients were eligible if they were aged 18 years or older; had one or two painful, stable, or potentially unstable vertebral metastases; and had a life expectancy of 1 year or longer according to the investigator's estimates. Patients received 48.5 grays (Gy) in 10 fractions (with epidural involvement) or 40 Gy in five fractions (without epidural involvement) in the SBRT group and 30 Gy in 10 fractions or 20 Gy in five fractions in the cEBRT group, respectively. The primary end point was an improvement in the pain score at the treated site by at least 2 points (on a visual analog scale from 0 to 10 points) at 6-month follow-up. Data were analyzed on an intention-to-treat and per-protocol basis. RESULTS: Of 214 patients who were screened for eligibility, 63 were randomized 1:1 between SBRT (33 patients with 36 metastases) and cEBRT (30 patients with 31 metastases). The median age of all patients was 66 years, and 40 patients were men (63.5%). In the intention-to-treat analysis, the 6-month proportion of patients who had metastases with pain reduction by 2 or more points was significantly higher in the SBRT group versus the control group (69.4% vs. 41.9%, respectively; two-sided p = .02). Changes in opioid medication intake relative to baseline were nonsignificant between the groups. No differences were observed in vertebral compression fracture or adverse event rates between the groups. CONCLUSIONS: Dose-intensified SBRT improved pain score more effectively than cEBRT at 6 months.

Radiotherapy concepts for spinal metastases-results from an online survey among radiation oncologists of the German Society for Radiation Oncology.

PURPOSE: Spinal metastases (SM) are a common radiotherapy (RT) indication. There is limited level I data to drive decision making regarding dose regimen (DR) and target volume definition (TVD). We aim to depict the patterns of care for RT of SM among German Society for Radiation Oncology (DEGRO) members. METHODS: An online survey on conventional RT and Stereotactic Body Radiation Therapy (SBRT) for SM, distributed via e­mail to all DEGRO members, was completed by 80 radiation oncologists between February 24 and April 29, 2022. Participation was voluntary and anonymous. RESULTS: A variety of DR was frequently used for conventional RT (primary: n = 15, adjuvant: n = 14). 30 Gy/10 fractions was reported most frequently. TVD in adjuvant RT was heterogenous, with a trend towards larger volumes. SBRT was offered in 65% (primary) and 21% (adjuvant) of participants' institutions. A variety of DR was reported (primary: n = 40, adjuvant: n = 27), most commonly 27 Gy/3 fractions and 30 Gy/5 fractions. 59% followed International Consensus Guidelines (ICG) for TVD. CONCLUSION: We provide a representative depiction of RT practice for SM among DEGRO members. DR and TVD are heterogeneous. SBRT is not comprehensively practiced, especially in the adjuvant setting. Further research is needed to provide a solid data basis for detailed recommendations.

Excellent long-term pain response and local control following postoperative radiotherapy in patients with multiple myeloma.

PURPOSE: Multiple myeloma is associated with osteolytic bone lesions, often requiring surgery of the spine and postoperative radiotherapy (RT). Although common, data for clinical and informed decision-making are sparse. In this monocentric retrospective study, we aim to report the outcome of patients who underwent spinal surgery and postoperative RT due to multiple myeloma. METHODS: A total of 54 patients with multiple myeloma who underwent prior spinal surgery and postoperative RT at our institution between 2009 and 2020 were analyzed. Spinal instability neoplastic score (SINS) and Bilsky score, posttherapeutic adverse events, clinical data, and outcomes were collected and analyzed. The primary endpoint of this study was overall survival (OS), secondary endpoints were progression-free survival (PFS), pain response, local control, and skeletal-related events (SRE). RESULTS: The 3­ and 5­year overall survival (OS) was 74.9% (95% confidence interval [CI]: 63.5-88.4%) and 58% (95% CI: 44.5-75.6%), respectively. Median survival was not reached and 75% survival was 34.3 months (95% CI: 28.7-95.4 months). Median follow-up was 63 months (95% CI: 49-94 months). The number of patients with good to adequate performance status (Karnofsky performance score [KPS] ≥ 70) significantly increased after surgery (p < 0.01). We observed no grade 3/4 toxicity and only 13 (24%) grade 1/2 adverse events. Two patients (4%) experienced SRE. Overall, 92% of patients reported reduced pain after radiotherapy, with 66% reporting complete pain response. There was no difference in pain response between patients with different Bilsky scores. Bisphosphonate therapy and lower Bilsky score at the start of RT were associated with improved OS in univariate analysis (all p < 0.05). Multivariate Cox regression confirmed a Bilsky score of 2 or 3 as an independent negative prognostic factor (HR 3.89; 95 CI 1.4-10.7; p < 0.01). We observed no in-field recurrences. CONCLUSION: In this study, we were able to show that the current standard of RT after spinal surgery of osteolytic lesions is safe. In addition, we observed a very low rate of SRE (4%) and no in-field recurrences, demonstrating the local efficacy of RT in multiple myeloma patients. Higher Bilsky scores were associated with worse OS in multivariate analysis, but had no effect on pain response.

Spinal and cervical nodal metastases in a patient with glioblastoma.

This article presents the rare case of a 54-year-old gentleman with primary glioblastoma developing multiple extracranial metastases 7 months after diagnosis. Initially, the patient complained of progressive headaches, confusion, and weakness of the left arm. Magnetic resonance imaging of the brain showed a right temporoparietal tumor with substantial surrounding subcortical edema and midline shift to the left. Two consecutive craniotomies resulted in complete microsurgical resection of the lesion. Histology was consistent with a World Health Organization grade IV, IDH-wildtype glioblastoma. Further treatment was standard chemoradiation including intensity-modulated radiotherapy with oral temozolomide chemotherapy. Seven months after diagnosis, the cranial lesion progressed, and the patient developed painful metastases in multiple bones and suspicious right-sided cervical lymph nodes. Immunohistochemistry and molecular signature supported the case of a metastatic glioblastoma. Further treatment was palliative radiotherapy of the spinal lesions along with symptomatic pain management. Extracranial metastasis of glioblastoma is a rare complication of which only a few cases have been reported in the literature. Little is known about the precise mechanisms of tumor dissemination and the appropriate treatment.

Intraoperative radiotherapy combined with spinal stabilization surgery-a novel treatment strategy for spinal metastases based on a first single-center experiences.

INTRODUCTION: Current treatment of spinal metastases (SM) aims on preserving spinal stability, neurological status, and functional status as well as achieving local control. It consists of spinal surgery followed by radiotherapy and/or systemic treatment. Adjuvant therapy usually starts with a delay of a few weeks to prevent wound healing issues. Intraoperative radiotherapy (IORT) has previously been successfully applied during brain tumor, breast and colorectal carcinoma surgery but not in SM, including unstable one, to date. In our case series, we describe the feasibility, morbidity and mortality of a novel treatment protocol for SM combining stabilization surgery with IORT. METHODS: Single center case series on patients with SM. Single session stabilization by navigated open or percutaneous procedure using a carbon screw-rod system followed by concurrent 50 kV photon-IORT (ZEISS Intrabeam). The IORT probe is placed via a guide canula using navigation, positioning is controlled by IOCT or 3D-fluroscopy enabling RT isodose planning in the OR. RESULTS: 15 (8 female) patients (71 ± 10y) received this treatment between 07/22 and 09/23. Median Spinal Neoplastic Instability Score was 8 [7-10] IQR. Most metastasis were located in the thoracic (n = 11, 73.3%) and the rest in the lumbar (n = 4, 26.7%) spine. 9 (60%) patients received open, 5 (33%) percutaneous stabilization and 1 (7%) decompression only. Mean length of surgery was 157 ± 45 min. Eleven patients had 8 and 3 had 4 screws placed. In 2 patients radiotherapy was not completed due to bending of the guide canula with consecutive abortion of IORT. All other patients received 8 Gy isodoses at mdn. 1.5 cm [1.1-1.9, IQR] depth during 2-6 min. The patients had Epidural Spinal Cord Compression score 1a-3. Seven patients (46.7%) experienced adverse events including 2 surgical site infection (one 65 days after surgery). CONCLUSION: 50 kV photon IORT for SM and consecutive unstable spine needing surgical intervention is safe and feasible and can be a promising technique in selected cases.

The role of spine stereotactic radiosurgery for patients with breast cancer metastases.

PURPOSE: Breast cancer that metastasizes to the spine is associated with low quality of life and poor survival. Radiosurgery has an increasing role in this patient population. This single-institution (2003-2023) study analyzes clinical outcomes and prognostic factors for patients who underwent spinal stereotactic radiosurgery (SSRS) for metastatic breast cancer. METHODS: Ninety patients (155 unique breast cancer spinal metastases) were treated with SSRS. The median age was 57 years (range: 35-88), and the median KPS was 80 (range: 40-100). Forty-two (27%) lesions were managed surgically prior to radiosurgery. At SSRS, 75 (48%) lesions impinged or compressed the spinal cord per the epidural spinal cord scale (ESCC). Seventy-nine (51%) lesions were categorized as potentially unstable or unstable by the Spinal Instability Neoplastic Score (SINS). RESULTS: The median follow-up was 15 months (range: 1-183). The median single-session tumor volume was 25.4 cc (range: 2-197), and the median single-fraction prescription dose was 17 Gy (range: 12-25). Seven (5%) lesions locally progressed. The 1-, 2-, and 5-year local control rates were 98%, 97%, and 92%, respectively. The median overall survival (OS) for the cohort was 32 months (range: 2-183). The 1-, 2-, and 5-year OS rates were 72%, 53%, and 30%, respectively. On univariate analysis, KPS ≥ 80 (p = 0.009, HR: 0.51, 95% CI: 0.31-0.84) was associated with improved OS. Patient-reported pain improved (68%), remained stable (29%), or worsened (3%) following radiosurgery. Fifteen (10%) radiation-induced toxicities were reported. CONCLUSIONS: Spinal radiosurgery is a safe and highly effective long-term treatment modality for metastases to the spine that originate from breast cancer.

Frequency of and risk factors associated with local recurrence after spinal stereotactic body radiation therapy without surgery.

PURPOSE: This study aimed to identify factors associated with local recurrence after spinal stereotactic body radiation therapy (SBRT), focusing on patient movement during treatment and tumor characteristics. METHODS: A total of 48 patients who underwent spinal SBRT alone without surgery from August 2017 to October 2022 were evaluated. Logistic regression analysis was conducted to identify factors associated with local recurrence, including patient movement and tumor characteristics such as soft tissue involvement and tumor volume. Patient movement during treatment was measured using cone beam computed tomography before and after irradiation. RESULTS: Among the included cases, 68.7% and 42.6% had soft tissue involvement and movement exceeding 1 mm, respectively. The median follow-up duration for local recurrence was 11.6 (range: 0.7-44.9) months, whereas the median duration to local recurrence was 6.3 months. Within 12 months, 29.3% of the patients experienced local recurrence, among whom 43.9% moved ≥ 1 mm during treatment, whereas 15.8% did not move. Univariable analysis found that both soft tissue involvement (OR = 10.3, 1.21-87.9; p = 0.033) and patient movement ≥ 1 mm (OR = 5.75, 1.45-22.8; p = 0.013) were associated with local recurrence. Multivariable analysis identified patient movement as an independent prognostic factor for local recurrence (OR = 5.15, 1.06-25.0; p = 0.042). CONCLUSION: Our results suggest that patient movement during spinal SBRT was associated with local recurrence, emphasizing the need for better immobilization techniques and shorter delivery times to improve tumor control.

Utility of molecular markers in predicting local control specific to lung cancer spine metastases treated with stereotactic body radiotherapy.

BACKGROUND AND PURPOSE: We report outcomes following spine stereotactic body radiotherapy (SBRT) in metastatic non-small cell lung cancer (NSCLC) and the significance of programmed death-ligand 1 (PD-L1) status, epidermal growth factor receptor (EGFR) mutation and timing of immune check point inhibitors (ICI) on local failure (LF). MATERIALS AND METHODS: 165 patients and 389 spinal segments were retrospectively reviewed from 2009 to 2021. Baseline patient characteristics, treatment and outcomes were abstracted. Primary endpoint was LF and secondary, overall survival (OS) and vertebral compression fracture (VCF). Multivariable analysis (MVA) evaluated factors predictive of LF and VCF. RESULTS: The median follow-up and OS were: 13.0 months (range, 0.5-95.3 months) and 18.4 months (95% CI 11.4-24.6). 52.1% were male and 76.4% had adenocarcinoma. Of the 389 segments, 30.3% harboured an EGFR mutation and 17.0% were PD-L1 ≥ 50%. The 24 months LF rate in PD-L1 ≥ 50% vs PD-L1 < 50% was 10.7% vs. 38.0%, and in EGFR-positive vs. negative was 18.1% vs. 30.0%. On MVA, PD-L1 status of ≥ 50% (HR 0.32, 95% CI 0.15-0.69, p = 0.004) significantly predicted for lower LF compared to PD-L1 < 50%. Lower LF trend was seen with ICI administration peri and post SBRT (HR 0.41, 95% CI 0.16-1.05, p = 0.062). On MVA, polymetastatic disease (HR 3.28, 95% CI 1.84-5.85, p < 0.0001) and ECOG ≥ 2 (HR 1.87, 95% CI 1.16-3.02, p = 0.011) significantly predicted for worse OS and absence of baseline VCF predicted for lower VCF rate (HR 0.20, 95% CI 0.10-0.39, p < 0.0001). CONCLUSION: We report a significant association of PD-L1 ≥ 50% status on improved LC rates from spine SBRT in NSCLC patients.

Changes in Spinal Instability After Conventional Radiotherapy for Painful Vertebral Bone Metastases.

OBJECTIVE: Precise assessment of spinal instability is critical before and after radiotherapy (RT) for evaluating the effectiveness of RT. Therefore, we retrospectively evaluated the efficacy of RT in spinal instability over a period of 6 months after RT, utilizing the spinal instability neoplastic score (SINS) in patients with painful spinal metastasis. We retrospectively evaluated 108 patients who received RT for painful vertebral metastasis in our institution. Mechanical pain at metastatic vertebrae, radiological responses of irradiated vertebrae, and spinal instability were assessed. Follow-up assessments were done at the start of and at intervals of 1, 2, 3, 4, and 6 months after RT, with the pain disappearing in 67%, 85%, 93%, 97%, and 100% of the patients, respectively. The median SINS were 8, 6, 6, 5, 5, and 4 at the beginning and after 1, 2, 3, 4, and 6 months of RT, respectively. Multivariate analysis revealed that posterolateral involvement of spinal elements (PLISE) was the only risk factor for continuous potentially unstable/unstable spine at 1 month. In conclusion, there was improvement of pain, and recalcification results in regaining spinal stability over time after RT although vertebral body collapse and malalignment occur in some irradiated vertebrae. Clinicians should pay attention to PLISE in predicting continuous potentially unstable/unstable spine.

Long-term outcomes following proton therapy for pediatric spinal low-grade glioma.

BACKGROUND: Due to its rarity, no standard treatment guidelines exist for pediatric spinal low-grade glioma (LGG-S). Proton therapy (PT) offers an attractive modality to minimize toxicity. Herein, we present the first published series of pediatric patients who received PT for progressive LGG-S. PROCEDURES: We identified eight consecutive patients with nonmetastatic LGG-S treated with PT. Cumulative incidence method was used to estimate local control (LC), freedom from distant metastases (FFDM), and freedom from progression (FFP). The Kaplan-Meier product limit method assessed overall survival (OS). Toxicity was assessed according to the Common Terminology Criteria for Adverse Events Version 5.0. RESULTS: Median age at diagnosis was 4 years. All patients underwent attempted resection and developed recurrence/progression prior to referral for PT, with median duration between initial surgery and PT of 4.4 years. Median age at the start of PT was 8 years. Most patients (n = 5) received PT as ≥third line treatment. Seven patients were treated with PT to the primary tumor. Most patients (n = 7) received between 45-50.4 CGE. Median follow up was 7.8 years. The 10-year estimates for LC, FFDM, FFP, and OS were 85, 88, 73, and 55%, respectively. One patient experienced malignant transformation and two developed pseudoprogression following PT. No pulmonary, gastrointestinal, or musculoskeletal toxicities were observed during or after PT. CONCLUSIONS: Despite negative selection bias our experience suggests PT for pediatric LGG-S offers long-term disease control with limited toxicity. The favorable therapeutic ratio of PT suggests it should be considered among first-line therapy in children with nonmetastatic, unresectable LGG-S.

Emergency radiation therapy in modern-day practice: Now or never, or never again ?

Radiation therapy plays a fundamental role in oncological emergencies such as superior vena cava syndrome (SVCS) and metastatic epidural spinal cord compression (MESCC). These are two examples of critical complications of metastatic cancer in terms of pain and functional impact (respiratory and/or neurological). The aim of this review is to explore the current indications, treatment options and outcomes for emergency radiotherapy regarding to these complications.Regarding SVCS, studies are mostly retrospective and unanimously demonstrated a beneficial effect of radiotherapy on symptom relief. Spinal cord compression remains an indication for urgent radiotherapy, and should be combined with surgery when possible. The innovative stereotactic body radiotherapy (SBRT) showed promising results, however this technique requires small volumes and more time preparation and therefore is often unsuitable for SVCS and MESCC emergencies.This review concluded that radiotherapy has a central role to play within a multimodal approach for SVCS and MESCC treatment. Further prospective studies are needed to confirm the effectiveness of radiation and establish the criteria for selecting patients to benefit from this treatment option.

Clinical performance of implanted devices used in surgical treatment of patients with spinal tumors: a systematic review.

PURPOSE: Implanted devices used in metastatic spine tumor surgery (MSTS) include pedicle screws, fixation plates, fixation rods, and interbody devices. A material to be used to fabricate any of these devices should possess an array of properties, which include biocompatibility, no toxicity, bioactivity, low wear rate, low to moderate incidence of artifacts during imaging, tensile strength and modulus that are comparable to those of cortical bone, high fatigue strength/long fatigue life, minimal or no negative impact on radiotherapy (RT) planning and delivery, and high capability for fusion to the contiguous bone. The shortcomings of Ti6Al4V alloy for these applications with respect to these desirable properties are well recognized, opening the field for an investigation about novel biomaterials that could replace the current gold standard. Previously published reviews on this topic have exhibited significant shortcomings in the studies they included, such as a small, heterogenous sample size and the lack of a cost-benefit analysis, extremely useful to understand the practical possibility of applying a novel material on a large scale. Therefore, this review aims to collect information about the clinical performance of these biomaterials from the most recent literature, with the objective of deliberating which could potentially be better than titanium in the future, with particular attention to safety, artifact production and radiotherapy planning interference. The significant promise showed by analyzing the clinical performance of these devices warrants further research through prospective studies with a larger sample size also taking into account each aspect of the production and use of such materials. METHODS: The Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines were used to improve the reporting of the review. The search was performed from March 2022 to September 2023. RESULTS: At the end of the screening process, 20 articles were considered eligible for this study. Polyetheretherketone (PEEK), Carbon-fibre reinforced polyetheretherketone (CFR-PEEK), long carbon fiber reinforced polymer (LCFRP), Polymethylmethacrylate (PMMA), and carbon screw and rods were used in the included studies. CONCLUSION: CFR-PEEK displays a noninferior safety and efficacy profile to titanium implanted devices. However, it also has other advantages. By decreasing artifact production, it is able to increase detection of local tumor recurrence and decrease radiotherapy dose perturbation, ultimately bettering prognosis for patients necessitating adjuvant treatment. Nonetheless, its drawbacks have not been explored fully and still require further investigation in future studies. This does not exclude the fact that CFR-PEEK could be a valid alternative to titanium in the near future.

Proton versus photon adjuvant radiotherapy: a multicenter comparative evaluation of recurrence following spinal chordoma resection.

OBJECTIVE: Chordomas are rare tumors of the skull base and spine believed to arise from the vestiges of the embryonic notochord. These tumors are locally aggressive and frequently recur following resection and adjuvant radiotherapy. Proton therapy has been introduced as a tissue-sparing option because of the higher level of precision that proton-beam techniques offer compared with traditional photon radiotherapy. This study aimed to compare recurrence in patients with chordomas receiving proton versus photon radiotherapy following resection by applying tree-based machine learning models. METHODS: The clinical records of all patients treated with resection followed by adjuvant proton or photon radiotherapy for chordoma at Mayo Clinic were reviewed. Patient demographics, type of surgery and radiotherapy, tumor recurrence, and other variables were extracted. Decision tree classifiers were trained and tested to predict long-term recurrence based on unseen data using an 80/20 split. RESULTS: Fifty-three patients with a mean ± SD age of 55.2 ± 13.4 years receiving surgery and adjuvant proton or photon therapy to treat chordoma were identified; most patients were male. Gross-total resection was achieved in 54.7% of cases. Proton therapy was the most common adjuvant radiotherapy (84.9%), followed by conventional or external-beam radiation therapy (9.4%) and stereotactic radiosurgery (5.7%). Patients receiving proton therapy exhibited a 40% likelihood of having recurrence, significantly lower than the 88% likelihood observed in those treated with nonproton therapy. This was confirmed on logistic regression analysis adjusted for extent of tumor resection and tumor location, which revealed that proton adjuvant radiotherapy was associated with a decreased risk of recurrence (OR 0.1, 95% CI 0.01-0.71; p = 0.047) compared with photon therapy. The decision tree algorithm predicted recurrence with an accuracy of 90% (95% CI 55.5%-99.8%), with the lowest risk of recurrence observed in patients receiving gross-total resection with adjuvant proton therapy (23%). CONCLUSIONS: Following resection, adjuvant proton therapy was associated with a lower risk of chordoma recurrence compared with photon therapy. The described machine learning models were able to predict tumor progression based on the extent of tumor resection and adjuvant radiotherapy modality used.

Influence of dose calculation algorithms on the helical diode array using volumetric-modulated arc therapy for small targets.

BACKGROUND: For patient-specific quality assurance (PSQA) for small targets, the dose resolution can change depending on the characteristics of the dose calculation algorithms. PURPOSE: This study aimed to evaluate the influence of the dose calculation algorithms Acuros XB (AXB), anisotropic analytical algorithm (AAA), photon Monte Carlo (pMC), and collapsed cone (CC) on a helical diode array using volumetric-modulated arc therapy (VMAT) for small targets. MATERIALS AND METHODS: ArcCHECK detectors were inserted with a physical depth of 2.9 cm from the surface. To evaluate the influence of the dose calculation algorithms for small targets, rectangular fields of 2×100, 5×100, 10×100, 20×100, 50×100, and 100×100 mm2 were irradiated and measured using ArcCHECK with TrueBeam STx. A total of 20 VMAT plans for small targets, including the clinical sites of 19 brain metastases and one spine, were also evaluated. The gamma passing rates (GPRs) were evaluated for the rectangular fields and the 20 VMAT plans using AXB, AAA, pMC, and CC. RESULTS: For rectangular fields of 2×100 and 5×100 mm2, the GPR at 3%/2 mm of AXB was < 50% because AXB resulted in a coarser dose resolution with narrow beams. For field sizes > 10×100 mm2, the GPR at 3%/2 mm was > 88.1% and comparable for all dose calculation algorithms. For the 20 VMAT plans, the GPRs at 3%/2 mm were 79.1 ± 15.7%, 93.2 ± 5.8%, 94.9 ± 4.1%, and 94.5 ± 4.1% for AXB, AAA, pMC, and CC, respectively. CONCLUSION: The behavior of the dose distribution on the helical diode array differed depending on the dose calculation algorithm for small targets. Measurements using ArcCHECK for VMAT with small targets can have lower GPRs owing to the coarse dose resolution of AXB around the detector area.

Efficacious patient-specific QA for Vertebra SBRT using a high-resolution detector array SRS MapCHECK: AAPM TG-218 analysis.

PURPOSE: Patient-specific quality assurance (PSQA) for vertebra stereotactic body radiation therapy (SBRT) presents challenges due to highly modulated small fields with high-dose gradients between the target and spinal cord. This study aims to explore the use of the SRS MapCHECK® (SRSMC) for vertebra SBRT PSQA. METHODS: Twenty vertebra SBRT treatment plans including prescriptions 20 Gy/1 fraction and 24 Gy/2 fractions were selected for each of Millennium (M)-Multileaf Collimator (MLC), and high-definition (HD)-MLC. All 40 plans were measured using Gafchromic EBT3 film (film) and SRSMC, using the StereoPHAN phantom. Plan complexity was assessed using modulation complexity score (MCS), edge metric (EM) (mm-1), modulation factor (MU/cGy), and average leaf pair opening (ALPO) (mm) and its correlation with gamma-pass rate was investigated. The high dose gradient between the target and the spinal cord was analyzed for film and SRSMC and compared against the treatment planning system (TPS). Applying the methodology proposed by AAPM TG-218, action and tolerance values specific to the SRSMC for vertebra SBRT were determined for ß values ranging from 5 to 8. RESULTS: Film and SRSMC gamma-pass rates showed no correlation (p > 0.05). A moderate negative correlation (R = -0.57, p = 0.01) is present between EM and SRSMC 3%/1 mm gamma-pass rate for HD-MLC plans. Both film and SRSMC accurately measured high dose gradients between the target and the spinal cord (R2 > 0.86, p ≤ 0.05). Notably, dose-gradient of HD-MLC plans is 22% steeper and has a smaller standard deviation to M-MLC plans (p ≤ 0.05). Applying TG-218, the film tolerance limit was 96% with action limit 95% for 5%/1 mm (ß = 6) and for the SRSMC tolerance limit was 97% with an action limit of 96% for 4%/1 mm (ß = 6). CONCLUSION: Our findings suggest that universal TG-218 limits may not be suitable for vertebra SBRT PSQA. This study demonstrates that SRSMC is a viable tool for vertebra SBRT PSQA, supported by TG-218 implementation of process-based tolerance and action limits.

Dosimetric impact of the respiratory motion of the liver dome in stereotactic body radiotherapy for spine metastasis: A planning study.

PURPOSE: This study aimed to clarify the dosimetric impact of the respiratory motion of the liver on stereotactic body radiation therapy (SBRT) for spine metastasis and examine the utility of introducing beam avoidance (beam-off at specific gantry angles). METHODS: A total of 112 consecutive patients who underwent SBRT for spine metastasis between 2018 and 2024 were examined. Overall, 15 patients who had lesions near the liver dome were included in this study. Retrospective treatment plans were generated using computed tomography (CT) images acquired during inhalation and exhalation to evaluate the dosimetric impact of respiratory motion of the liver. The dose difference (DD) and relative value (DD%) were evaluated using the dose-volume histogram (DVH) metrics, planning target volume Dmax, D95%, spinal cord D0.035 cc, and esophagus D2.5 cc. The magnitude of the liver movements was evaluated based on differences of liver size Lave at the isocentric axial plane between the inspiratory and expiratory CT images. RESULTS: The DD in almost all DVH metrics tended to increase when the liver moved away from the target during inhalation: For example, Mean ± $ \pm $ a standard deviation (SD) DD in PTV D95% for the treatment plan incorporating beam avoidance and those without beam avoidance was 0.5 ± $\pm$ 0.3 and 0.9 ± $ \pm $ 0.6 Gy, respectively. The spinal cord D0.035 cc for those shows 0.4 ± $ \pm $ 0.2 and 0.7 ± $ \pm $ 0.7 Gy, respectively. The treatment plans without beam avoidance also showed moderate or strong correlations between Lave and DD for almost all DVH metrics. No correlation was seen in the beam avoidance plan. The spinal cord D0.035 cc revealed approximately 1 Gy or +4% in DD when Lave was < -4 cm. CONCLUSIONS: Respiratory motion of the liver dome can cause substantial dosimetric discrepancies in the dose delivered to the spinal cord, although the extent depends on patient variables. Dose assessment should be performed for determining the appropriate means of respiratory management, such as breath-hold. Alternatively, beam avoidance effectively mitigates the impact.

Role of Proton Beam Therapy in Spinal Chordomas: A Narrative Review of The Literature.

Chordomas are rare malignant neoplasms arising from vestigial remnants of the embryonic notochord. Approximately 55-70% of chordomas develop within the vertebral column. Their affinity to develop within the bones of the axial skeleton and propensity to locally invade and recur makes them challenging candidates for complete surgical excision. Adjuvant therapies are hence necessary to improve outcomes; for which chemotherapy has been observed to be largely ineffective, owing to the tumour being resistant to it. Radiotherapy is the current adjuvant therapy of choice for chordoma management. Over the years, proton beam therapy (PBT) has been the subject of medical attention, given the dosimetric benefits it confers over traditional radiotherapy, allowing more concentrated radiation to be given to the target of interest and reducing damage to surrounding normal tissue. A review of the current literature reveals PBT offers significantly better outcomes when used as an adjuvant to maximal surgical resection rather than as a definitive therapy.

Increased Dose in Spine Stereotactic Radiosurgery for Metastatic Disease: Are We Underestimating the Risks?

Background and Objectives: The recently published Spine Stereotactic Radiosurgery (SSRS) ESTRO guidelines advise against treating spinal metastatic disease with a single dose equal to or smaller than 18 Gy, prioritizing local control over the potential for complications. This study aims to assess the necessity and validity of these higher dose recommendations by evaluating the outcomes and experiences with lower radiation doses. Materials and Methods: A retrospective evaluation of SSRS patients treated at a single institute was conducted. The outcomes and complications of this cohort were compared to the current literature and the data supporting the new ESTRO guidelines. Results: A total of 149 treatment sessions involving 242 spinal levels were evaluated. The overall local control rate was 91.2%. The mean radiation dose for the local control group compared to the local failure group was similar (17.5 vs. 17.6 Gy, not significant). The overall complication rate was 6%. These results are consistent with previous publications evaluating SSRS for metastatic spinal disease. Conclusions: SSRS dose escalation may increase local control efficacy but comes with a higher risk of complications. The evidence supporting the strong recommendations in the recent ESTRO guidelines is not robust enough to justify a universal application. Given the palliative nature of treatment for metastatic patients, dose determination should be individualized based on patient conditions and preferences, with a detailed discussion about the risk-benefit ratio of increased doses and the level of evidence supporting these recommendations.

Spine Instability Neoplastic Score (SINS) as a Predictive Tool in Conventional Radiotherapy: A Narrative Review.

AIMS: This narrative review seeks to identify the SINS score application in the radiation oncology field. METHODS: This literature review was performed searching papers on MEDLINE published from January 2010 to August 2022. RESULTS: In terms of vertebral painful lesions and RT symptomatic responses, the SINS score could be an interesting aid in order to choose the right therapeutic approach. Lesions with higher level of instability, and therefore higher SINS score, could did not find any significant benefit from radiation therapy which is more effective on the tumor-related pain component. For SINS as a predictor of adverse event after RT or its changes after RT, we obtained contrasting results. CONCLUSIONS: The reported few experiences showed ambiguous conclusions. Further prospective studies are needed.