Longitudinal Neuropathological Consequences of Extracranial Radiation Therapy in Mice.

Cancer-related cognitive impairment (CRCI) is a consequence of chemotherapy and extracranial radiation therapy (ECRT). Our prior work demonstrated gliosis in the brain following ECRT in SKH1 mice. The signals that induce gliosis were unclear. Right hindlimb skin from SKH1 mice was treated with 20 Gy or 30 Gy to induce subclinical or clinical dermatitis, respectively. Mice were euthanized at 6 h, 24 h, 5 days, 12 days, and 25 days post irradiation, and the brain, thoracic spinal cord, and skin were collected. The brains were harvested for spatial proteomics, immunohistochemistry, Nanostring nCounter® glial profiling, and neuroinflammation gene panels. The thoracic spinal cords were evaluated by immunohistochemistry. Radiation injury to the skin was evaluated by histology. The genes associated with neurotransmission, glial cell activation, innate immune signaling, cell signal transduction, and cancer were differentially expressed in the brains from mice treated with ECRT compared to the controls. Dose-dependent increases in neuroinflammatory-associated and neurodegenerative-disease-associated proteins were measured in the brains from ECRT-treated mice. Histologic changes in the ECRT-treated mice included acute dermatitis within the irradiated skin of the hindlimb and astrocyte activation within the thoracic spinal cord. Collectively, these findings highlight indirect neuronal transmission and glial cell activation in the pathogenesis of ECRT-related CRCI, providing possible signaling pathways for mitigation strategies.

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.

Effects of Photon versus Carbon-Ion Irradiation in the Rat Cervical Spinal Cord - a Serial T2 and Diffusion-weighted Magnetic Resonance Imaging Study.

Carbon-ion irradiation is increasingly used at the skull base and spine near the radiation-sensitive spinal cord. To better characterize the in vivo radiation response of the cervical spinal cord, radiogenic changes in the high-dose area were measured in rats using magnetic resonance imaging (MRI) diffusion measurements in comparison to conventional photon irradiations. In this longitudinal MRI study, we examined the gray matter (GM) of the cervical spinal cord in 16 female Sprague-Dawley rats after high-dose photon (n = 8) or carbon-ion (12C) irradiation (n = 8) and in 6 sham-exposed rats until myelopathy occurred. The differences in the diffusion pattern of the GM of the cervical spinal cord were examined until the endpoint of the study, occurrence of paresis grade II of both forelimbs was reached. In both radiation techniques, the same order of the occurrence of MR-morphological pathologies was observed - from edema formation to a blood spinal cord barrier (BSCB) disruption to paresis grade II of both forelimbs. However, carbon-ion irradiation showed a significant increase of the mean apparent diffusion coefficient (ADC; P = 0.031) with development of a BSCB disruption in the GM. Animals with paresis grade II as a late radiation response had a highly significant increase in mean ADC (P = 0.0001) after carbon-ion irradiation. At this time, a tendency was observed for higher mean ADC values in the GM after 12C irradiation as compared to photon irradiation (P = 0.059). These findings demonstrated that carbon-ion irradiation leads to greater structural damage to the GM of the rat cervical spinal cord than photon irradiation due to its higher linear energy transfer (LET) value.

Radiation-induced bystander effect on the brain after fractionated spinal cord irradiation of aging rats.

We investigated the influence of the so-called bystander effect on metabolic and histopathological changes in the rat brain after fractionated spinal cord irradiation. The study was initiated with adult Wistar male rats (n = 20) at the age of 9 months. The group designated to irradiation (n = 10) and the age-matched control animals (n = 10) were subjected to an initial measurement using in vivo proton magnetic resonance spectroscopy (1H MRS) and magnetic resonance imaging (MRI). After allowing the animals to survive until 12 months, they received fractionated spinal cord irradiation with a total dose of 24 Gy administered in 3 fractions (8 Gy per fraction) once a week on the same day for 3 consecutive weeks. 1H MRS and MRI of brain metabolites were performed in the hippocampus, corpus striatum, and olfactory bulb (OB) before irradiation (9-month-old rats) and subsequently 48 h (12-month-old) and 2 months (14-month-old) after the completion of irradiation. After the animals were sacrificed at the age of 14 months, brain tissue changes were investigated in two neurogenic regions: the hippocampal dentate gyrus (DG) and the rostral migratory stream (RMS). By comparing the group of 9-month-old rats and individuals measured 48 h (at the age of 12 months) after irradiation, we found a significant decrease in the ratio of total N-acetyl aspartate to total creatine (tNAA/tCr) and gamma-aminobutyric acid to tCr (GABA/tCr) in OB and hippocampus. A significant increase in myoinositol to tCr (mIns/tCr) in the OB persisted up to 14 months of age. Proton nuclear magnetic resonance (1H NMR)-based plasma metabolomics showed a significant increase in keto acids and decreased tyrosine and tricarboxylic cycle enzymes. Morphometric analysis of neurogenic regions of 14-month-old rats showed well-preserved stem cells, neuroblasts, and increased neurodegeneration. The radiation-induced bystander effect more significantly affected metabolite concentration than the distribution of selected cell types.

Characterizing Proton-Induced Biological Effects in a Mouse Spinal Cord Model: A Comparison of Bragg Peak and Entrance Beam Response in Single and Fractionated Exposures.

PURPOSE: Proton relative biological effectiveness (RBE) is a dynamic variable influenced by factors like linear energy transfer (LET), dose, tissue type, and biological endpoint. The standard fixed proton RBE of 1.1, currently used in clinical planning, may not accurately represent the true biological effects of proton therapy (PT) in all cases. This uncertainty can contribute to radiation-induced normal tissue toxicity in patients. In late-responding tissues such as the spinal cord, toxicity can cause devastating complications. This study investigated spinal cord tolerance in mice subjected to proton irradiation and characterized the influence of fractionation on proton- induced myelopathy at entrance (ENT) and Bragg peak (BP) positions. METHODS AND MATERIALS: Cervical spinal cords of 8-week-old C57BL/6J female mice were irradiated with single- or multi-fractions (18x) using lateral opposed radiation fields at 1 of 2 positions along the Bragg curve: ENT (dose-mean LET = 1.2 keV/µm) and BP (LET = 6.9 keV/µm). Mice were monitored over 1 year for changes in weight, mobility, and general health, with radiation-induced myelopathy as the primary biological endpoint. Calculations of the RBE of the ENT and BP curve (RBEENT/BP) were performed. RESULTS: Single-fraction RBEENT/BP for 50% effect probability (tolerance dose (TD50), grade II paresis, determined using log-logistic model fitting) was 1.10 ± 0.06 (95% CI) and for multifraction treatments it was 1.19 ± 0.05 (95% CI). Higher incidence and faster onset of paralysis were seen in mice treated at the BP compared with ENT. CONCLUSIONS: The findings challenge the universally fixed RBE value in PT, indicating up to a 25% mouse spinal cord RBEENT/BP variation for multifraction treatments. These results highlight the importance of considering fractionation in determining RBE for PT. Robust characterization of proton-induced toxicity, aided by in vivo models, is paramount for refining clinical decision-making and mitigating potential patient side effects.

Management of reirradiations: A clinical and technical overview based on a French survey.

INTRODUCTION: The reirradiation number increased due to systemic therapies and patient survival. Few guidelines regarding acceptable cumulative doses to organs at risk (OARs) and appropriate dose accumulation tools need, made reirradiation challenging. The survey objective was to present the French current technical and clinical practices in reirradiations. METHODS: A group of physician and physicists developed a survey gathering major issues of the topic. The questionnaire consisted in 4 parts: data collection, demographic, clinical and technical aspects. It was delivered through the SFRO and the SFPM. Data collection lasted 2 months and were gathered to compute statistical analysis. RESULTS: 48 institutions answered the survey. Difficulties about patient data collection were related to patient safety, administrative and technical limitations. Half of the institutions discussed reirradiation cases during a multidisciplinary meeting. It mainly aimed at discussing the indication and the new treatment total dose (92%). 79% of the respondents used various references but only 6% of them were specific to reirradiations. Patients with pain and clinical deficit were ranked as best inclusion criteria. 54.2% of the institutions considered OARs recovery, especially for spinal cord and brainstem. A commercial software was used for dose accumulation for 52% of respondents. Almost all institutions performed equivalent dose conversion (94%). A quarter of the institutions estimated not to have the appropriate equipment for reirradiation. CONCLUSION: This survey showed the various approaches and tools used in reirradiation management. It highlighted issues in collecting data, and the guidelines necessity for safe practices, to increase clinicians confidence in retreating patients.

Bicentric Treatment Outcomes After Proton Therapy for Nonmyxopapillary High-Grade Spinal Cord Ependymoma in Children.

PURPOSE: Few studies report outcomes in children treated with radiation for nonmyxopapillary ependymoma of the spinal cord, and little evidence exists to inform decisions regarding target volume and prescription dose. Moreover, virtually no mature outcome data exist on proton therapy for this tumor. We describe our combined institutional experience treating pediatric classical/anaplastic ependymoma of the spinal cord with proton therapy. METHODS AND MATERIALS: Between 2008 and 2019, 14 pediatric patients with nonmetastatic nonmyxopapillary grade II (n = 6) and grade III (n = 8) spinal ependymoma received proton therapy. The median age at radiation was 14 years (range, 1.5-18 years). Five tumors arose within the cervical cord, 3 within the thoracic cord, and 6 within the lumbosacral cord. Before radiation therapy, 3 patients underwent subtotal resection, and 11 underwent gross-total or near total resection. Two patients received chemotherapy. For radiation, the clinical target volume received 50.4 Gy (n = 8), 52.2 (n = 1), or 54 Gy (n = 5), with the latter receiving a boost to the gross tumor volume after the initial 50.4 Gy, modified to respect spinal cord tolerance. RESULTS: With a median follow-up of 6.3 years (range, 1.5-14.8 years), no tumors progressed. Although most patients experienced neurologic sequela after surgery, only 1 developed additional neurologic deficits after radiation: An 18-year-old male who received 54 Gy after gross total resection of a lumbosacral tumor developed grade 2 erectile dysfunction. There were 2 cases of musculoskeletal toxicity attributable to surgery and radiation. At analysis, no patient had developed cardiac, pulmonary, or other visceral organ complications or a second malignancy. CONCLUSION: Radiation to a total dose of 50 to 54 Gy can be safely delivered and plays a beneficial role in the multidisciplinary management of children with nonmyxopapillary spinal cord ependymoma. Proton therapy may reduce late radiation effects and is not associated with unexpected spinal cord toxicity.

New clinical data on human spinal cord re-irradiation tolerance.

PURPOSE: To provide additional clinical data about the re-irradiation tolerance of the spinal cord. METHODS: This was a retrospective bi-institutional study of patients re-irradiated to the cervical or thoracic spinal cord with minimum follow-up of 6 months. The maximum dose (Dmax) and dose to 0.1cc (D0.1cc) were determined (magnetic resonance imaging [MRI]-defined cord) and expressed as equivalent dose in 2­Gy fractions (EQD2) with an α/ß value of 2 Gy. RESULTS: All 32 patients remained free from radiation myelopathy after a median follow-up of 12 months. Re-irradiation was performed after 6-97 months (median 15). In 22 cases (69%) the re-irradiation spinal cord EQD2 Dmax was higher than that of the first treatment course. Forty-eight of 64 treatment courses employed fraction sizes of 2.5 to 4 Gy to the target volume. The median cumulative spinal cord EQD2 Dmax was 80.7 Gy, minimum 61.12 Gy, maximum 114.79 Gy. The median cumulative spinal cord D0.1cc EQD2 was 76.1 Gy, minimum 61.12 Gy, maximum 95.62 Gy. Besides cumulative dose, other risk factors for myelopathy were present (single-course Dmax EQD2 ≥51 Gy in 9 patients, single-course D0.1cc EQD2 ≥51 Gy in 5 patients). CONCLUSION: Even patients treated to higher cumulative doses than previously recommended, or at a considerable risk of myelopathy according to a published risk score, remained free from this complication, although one must acknowledge the potential for manifestation of damage in patients currently alive, i.e., still at risk. Individualized decisions to re-irradiate after appropriate informed consent are an acceptable strategy, including scenarios where low re-irradiation doses to the spinal cord would compromise target coverage and tumor control probability to an unacceptable degree.

Longitudinal MRI study after carbon ion and photon irradiation: shorter latency time for myelopathy is not associated with differential morphological changes.

BACKGROUND: Radiation-induced myelopathy is a severe and irreversible complication that occurs after a long symptom-free latency time if the spinal cord was exposed to a significant irradiation dose during tumor treatment. As carbon ions are increasingly investigated for tumor treatment in clinical trials, their effect on normal tissue needs further investigation to assure safety of patient treatments. Magnetic resonance imaging (MRI)-visible morphological alterations could serve as predictive markers for medicinal interventions to avoid severe side effects. Thus, MRI-visible morphological alterations in the rat spinal cord after high dose photon and carbon ion irradiation and their latency times were investigated. METHODS: Rats whose spinal cords were irradiated with iso-effective high photon (n = 8) or carbon ion (n = 8) doses as well as sham-treated control animals (n = 6) underwent frequent MRI measurements until they developed radiation-induced myelopathy (paresis II). MR images were analyzed for morphological alterations and animals were regularly tested for neurological deficits. In addition, histological analysis was performed of animals suffering from paresis II compared to controls. RESULTS: For both beam modalities, first morphological alterations occurred outside the spinal cord (bone marrow conversion, contrast agent accumulation in the musculature ventral and dorsal to the spinal cord) followed by morphological alterations inside the spinal cord (edema, syrinx, contrast agent accumulation) and eventually neurological alterations (paresis I and II). Latency times were significantly shorter after carbon ions as compared to photon irradiation. CONCLUSIONS: Irradiation of the rat spinal cord with photon or carbon ion doses that lead to 100% myelopathy induced a comparable fixed sequence of MRI-visible morphological alterations and neurological distortions. However, at least in the animal model used in this study, the observed MRI-visible morphological alterations in the spinal cord are not suited as predictive markers to identify animals that will develop myelopathy as the time between MRI-visible alterations and the occurrence of myelopathy is too short to intervene with protective or mitigative drugs.

Dosimetric Assessment of a High Precision System for Mouse Proton Irradiation to Assess Spinal Cord Toxicity.

The uncertainty associated with the relative biological effectiveness (RBE) in proton therapy, particularly near the Bragg peak (BP), has led to the shift towards biological-based treatment planning. Proton RBE uncertainty has recently been reported as a possible cause for brainstem necrosis in pediatric patients treated with proton therapy. Despite this, in vivo studies have been limited due to the complexity of accurate delivery and absolute dosimetry. The purpose of this investigation was to create a precise and efficient method of treating the mouse spinal cord with various portions of the proton Bragg curve and to quantify associated uncertainties for the characterization of proton RBE. Mice were restrained in 3D printed acrylic boxes, shaped to their external contour, with a silicone insert extending down to mold around the mouse. Brass collimators were designed for parallel opposed beams to treat the spinal cord while shielding the brain and upper extremities of the animal. Up to six animals may be accommodated for simultaneous treatment within the restraint system. Two plans were generated targeting the cervical spinal cord, with either the entrance (ENT) or the BP portion of the beam. Dosimetric uncertainty was measured using EBT3 radiochromic film with a dose-averaged linear energy transfer (LETd) correction. Positional uncertainty was assessed by collecting a library of live mouse scans (n = 6 mice, two independent scans per mouse) and comparing the following dosimetric statistics from the mouse cervical spinal cord: Volume receiving 90% of the prescription dose (V90); mean dose to the spinal cord; and LETd. Film analysis results showed the dosimetric uncertainty to be ±1.2% and ±5.4% for the ENT and BP plans, respectively. Preliminary results from the mouse library showed the V90 to be 96.3 ± 4.8% for the BP plan. Positional uncertainty of the ENT plan was not measured due to the inherent robustness of that treatment plan. The proposed high-throughput mouse proton irradiation setup resulted in accurate dose delivery to mouse spinal cords positioned along the ENT and BP. Future directions include adapting the setup to account for weight fluctuations in mice undergoing fractionated irradiation.

Interstitial single fraction brachytherapy for malignant pulmonary tumours.

PURPOSE: Interstitial brachytherapy for pulmonary tumours is an alternative to stereotactic radiotherapy, allowing high conformity despite it being an invasive technique. The aim of the study was the analysis of dose distribution, toxicity and tumour response rates. METHODS: In the years 2014-2019, 27 patients with pulmonary tumours received 36 interstitial brachytherapies with Ir-192: 11 patients with non-small cell lung cancer, 16 patients with pulmonary metastases of other entities. RESULTS: Patients were treated with a median (interquartile range) prescription dose of 20 (20-26) Gy in a single fraction. Mean lung dose to the ipsilateral lung was 2.8 (1.6-4.7) Gy. Maximum doses to the heart, oesophagus, thoracic wall and spinal cord were 2.4 (1.8-4.6) Gy, 2.0 (1.2-6.2) Gy, 12.6 (8.0-18.2) Gy and 1.5 (0.6-3.9) Gy. Median survival after treatment was 15 months, with a 1- and 2­year local control of 84% and 60%. Median overall survival after initial cancer diagnosis was 94 months; 2 years following brachytherapy, 75% of patients with colorectal cancer vs. 37% with other histologies were alive; p = 0.14. In 69% (n = 25), brachytherapy could be performed without acute complications. A self-limiting bleeding occurred in 8% (n = 3), fever in 3% (n = 1), pneumothorax in 17% (n = 6), and pulmonary failure in 3% (n = 1). Patients with > 20 Gy in 95% of planning target volume had higher pneumothorax rates needing intervention (31% vs. 5%, p = 0.04). CONCLUSIONS: Interstitial brachytherapy for pulmonary tumours is a highly conformal therapy with minimal doses to the organs at risk. For the majority of patients, treatment can be performed without relevant complications in a single fraction with a satisfactory local control.

Initial Data Pooling for Radiation Dose-Volume Tolerance for Carotid Artery Blowout and Other Bleeding Events in Hypofractionated Head and Neck Retreatments.

PURPOSE: Dose-volume data for injury to carotid artery and other major vessels in stereotactic body radiation therapy (SBRT)/SABR head and neck reirradiation were reviewed, modeled, and summarized. METHODS AND MATERIALS: A PubMed search of the English-language literature (stereotactic and carotid and radiation) in April 2018 found 238 major vessel maximum point doses in 6 articles that were pooled for logistic modeling. Two subsequent studies with dose-volume major vessel data were modeled separately for comparison. Attempts were made to separate carotid blowout syndrome from other bleeding events (BE) in the analysis, but we acknowledge that all except 1 data set has some element of BE interspersed. RESULTS: Prior radiation therapy (RT) dose was not uniformly reported per patient in the studies included, but a course on the order of conventionally fractionated 70 Gy was considered for the purposes of the analysis (with an approximately ≥6-month estimated interval between prior and subsequent treatment in most cases). Factors likely associated with reduced risk of BE include nonconsecutive daily treatment, lower extent of circumferential tumor involvement around the vessel, and no surgical manipulation before or after SBRT. CONCLUSIONS: Initial data pooling for reirradiation involving the carotid artery resulted in 3 preliminary models compared in this Hypofractionated Treatment Effects in the Clinic (HyTEC) report. More recent experiences with alternating fractionation schedules and additional risk-reduction strategies are also presented. Complications data for the most critical structures such as spinal cord and carotid artery are so limited that they cannot be viewed as strong conclusions of probability of risk, but rather, as a general guideline for consideration. There is a great need for better reporting standards as noted in the High Dose per Fraction, Hypofractionated Treatment Effects in the Clinic introductory paper.

Cumulative dose, toxicity, and outcomes of spinal metastases re-irradiation : Systematic review on behalf of the Re-Irradiation Working Group of the Italian Association of Radiotherapy and Clinical Oncology (AIRO).

PURPOSE: The aim of this study was to identify patient-, tumor-, or treatment-related factors which may affect disease-related outcomes of re-irradiation (reRT) in patients with previously irradiated vertebral metastases. METHODS: A computerized search of the literature was performed by searching for terms related to reRT and spinal metastases in MEDLINE, EMBASE, OVID, and the Cochrane database from 1995 to 2019. Studies including at least 10 patients who had received reRT at the same site of initial radiotherapy for vertebral metastases with localized external beam radiotherapy were included. To determine the pooled ≥G3 acute and late toxicity rate, pain relief, local control, and overall survival, a meta-analysis technique of single-arm studies was performed. RESULTS: Nineteen studies including 1373 patients met the inclusion criteria for this systematic review. The pooled pain relief, neurological improvement, 1­year local control, and 1­year overall survival rates were 74.3%, 73.8%, 78.8%, and 54.6%, respectively, with moderate to high heterogeneity among studies. No difference in heterogeneity was evidenced for pain relief or local control after omitting studies not using stereotactic body radiotherapy (SBRT) or studies delivering biologically effective dose (BED) < 45 Gy10, whereas heterogeneity for 1­year OS was lower after omitting studies not using SBRT and delivering BED < 45 Gy10. The pooled results of grade ≥ 3 acute and late toxicity were 0.4% (95% confidence interval: 0.1-1.2%) and 2.2% (95% confidence interval: 1.2-37%), respectively, with low heterogeneity among studies. CONCLUSION: While this systematic review confirmed that reRT is both safe and effective for treating patients with recurrent spinal metastases, it could not identify factors which may affect outcomes of reRT in this patient population.

Spinal Cord Dose Tolerance to Stereotactic Body Radiation Therapy.

Spinal cord tolerance data for stereotactic body radiation therapy (SBRT) were extracted from published reports, reviewed, and modelled. For de novo SBRT delivered in 1 to 5 fractions, the following spinal cord point maximum doses (Dmax) are estimated to be associated with a 1% to 5% risk of radiation myelopathy (RM): 12.4 to 14.0 Gy in 1 fraction, 17.0 Gy in 2 fractions, 20.3 Gy in 3 fractions, 23.0 Gy in 4 fractions, and 25.3 Gy in 5 fractions. For reirradiation SBRT delivered in 1 to 5 fractions, reported factors associated with a lower risk of RM include cumulative thecal sac equivalent dose in 2 Gy fractions with an alpha/beta of 2 (EQD22) Dmax ≤70 Gy; SBRT thecal sac EQD22 Dmax ≤25 Gy, thecal sac SBRT EQD22 Dmax to cumulative EQD22 Dmax ratio ≤0.5, and a minimum time interval to reirradiation of ≥5 months. Larger studies containing complete institutional cohorts with dosimetric data of patients treated with spine SBRT, with and without RM, are required to refine RM risk estimates.

Radiation Disrupts the Protective Function of the Spinal Meninges in a Mouse Model of Tumor-induced Spinal Cord Compression.

BACKGROUND: Recent advances in multidisciplinary treatments for various cancers have extended the survival period of patients with spinal metastases. Radiotherapy has been widely used to treat spinal metastases; nevertheless, long-term survivors sometimes undergo more surgical intervention after radiotherapy because of local tumor relapse. Generally, intradural invasion of a spinal tumor seldom occurs because the dura mater serves as a tissue barrier against tumor infiltration. However, after radiation exposure, some spinal tumors invade the dura mater, resulting in leptomeningeal dissemination, intraoperative dural injury, or postoperative local recurrence. The mechanisms of how radiation might affect the dura have not been well-studied. QUESTIONS/PURPOSES: To investigate how radiation affects the spinal meninges, we asked: (1) What is the effect of irradiation on the meningeal barrier's ability to protect against carcinoma infiltration? (2) What is the effect of irradiation on the meningeal barrier's ability to protect against sarcoma infiltration? (3) What is the effect of irradiation on dural microstructure observed by scanning electron microscopy (SEM)? (4) What is the effect of irradiation on dural microstructure observed by transmission electron microscopy (TEM)? METHODS: Eighty-four 10-week-old female ddY mice were randomly divided into eight groups: mouse mammary tumor (MMT) implantation 6 weeks after 0-Gy irradiation (nonirradiation) (n = 11), MMT implantation 6 weeks after 20-Gy irradiation (n = 10), MMT implantation 12 weeks after nonirradiation (n = 10), MMT implantation 12 weeks after 20-Gy irradiation (n = 11), mouse osteosarcoma (LM8) implantation 6 weeks after nonirradiation (n = 11), LM8 implantation 6 weeks after 20-Gy irradiation (n = 11), LM8 implantation 12 weeks after nonirradiation (n = 10), and LM8 implantation 12 weeks after 20-Gy irradiation (n = 10); female mice were used for a mammary tumor metastasis model and ddY mice, a closed-colony mice with genetic diversity, were selected to represent interhuman diversity. Mice in each group underwent surgery to generate a tumor-induced spinal cord compression model at either 6 weeks or 12 weeks after irradiation to assess changes in the meningeal barrier's ability to protect against tumor infiltration. During surgery, the mice were implanted with MMT (representative of a carcinoma) or LM8 tumor. When the mice became paraplegic because of spinal cord compression by the growing implanted tumor, they were euthanized and evaluated histologically. Four mice died from anesthesia and 10 mice per group were euthanized (MMT-implanted groups: MMT implantation occurred 6 weeks after nonirradiation [n = 10], 6 weeks after irradiation [n = 10], 12 weeks after nonirradiation [n = 10], and 12 weeks after irradiation [n = 10]; LM8-implanted groups: LM8 implantation performed 6 weeks after nonirradiation [n = 10], 6 weeks after irradiation [n = 10], 12 weeks after nonirradiation [n = 10], and 12 weeks after irradiation [n = 10]); 80 mice were evaluated. The spines of the euthanized mice were harvested; hematoxylin and eosin staining and Masson's trichrome staining slides were prepared for histologic assessment of each specimen. In the histologic assessment, intradural invasion of the implanted tumor was graded in each group by three observers blinded to the type of tumor, presence of irradiation, and the timing of the surgery. Grade 0 was defined as no intradural invasion with intact dura mater, Grade 1 was defined as intradural invasion with linear dural continuity, and Grade 2 was defined as intradural invasion with disruption of the dural continuity. Additionally, we euthanized 12 mice for a microstructural analysis of dura mater changes by two observers blinded to the presence of irradiation. Six mice (three mice in the 12 weeks after nonirradiation group and three mice in the 12 weeks after 20-Gy irradiation group) were quantitatively analyzed for defects on the dural surface with SEM. The other six mice (three mice in the 12 weeks after nonirradiation group and three mice in the 12 weeks after 20-Gy irradiation group) were analyzed for layer structure of collagen fibers constituting dura mater by TEM. In the SEM assessment, the number and size of defects on the dural surface on images (200 µm × 300 µm) at low magnification (× 2680) were evaluated. A total of 12 images (two per mouse) were evaluated for this assessment. The days from surgery to paraplegia were compared between each of the tumor groups using the Kruskal-Wallis test. The scores of intradural tumor invasion grades and the number of defects on dural surface per SEM image were compared between irradiation group and nonirradiation group using the Mann-Whitney U test. Interobserver reliabilities of assessing intradural tumor invasion grades and the number of dural defects on the dural surface were analyzed using Fleiss'κ coefficient. P values < 0.05 were considered statistically significant. RESULTS: There was no difference in the median (range) time to paraplegia among the MMT implantation 6 weeks after nonirradiation group, the 6 weeks after irradiation group, the 12 weeks after nonirradiation group, and the 12 weeks after irradiation group (16 days [14 to 17] versus 14 days [12 to 18] versus 16 days [14 to 17] versus 14 days [12 to 15]; χ2 = 4.7; p = 0.19). There was also no difference in the intradural invasion score between the MMT implantation 6 weeks after irradiation group and the 6 weeks after nonirradiation group (8 of 10 Grade 0 and 2 of 10 Grade 1 versus 10 of 10 Grade 0; p = 0.17). On the other hand, there was a higher intradural invasion score in the MMT implantation 12 weeks after irradiation group than the 12 weeks after nonirradiation group (5 of 10 Grade 0, 3 of 10 Grade 1 and 2 of 10 Grade 2 versus 10 of 10 Grade 0; p = 0.02). Interobserver reliability of assessing intradural tumor invasion grades in the MMT-implanted group was 0.94. There was no difference in the median (range) time to paraplegia among in the LM8 implantation 6 weeks after nonirradiation group, the 6 weeks after irradiation group, the 12 weeks after nonirradiation group, and the 12 weeks after irradiation group (12 days [9 to 13] versus 10 days [8 to 13] versus 11 days [8 to 13] versus 9 days [6 to 12]; χ2 = 2.4; p = 0.50). There was also no difference in the intradural invasion score between the LM8 implantation 6 weeks after irradiation group and the 6 weeks after nonirradiation group (7 of 10 Grade 0, 1 of 10 Grade 1 and 2 of 10 Grade 2 versus 8 of 10 Grade 0 and 2 of 10 Grade 1; p = 0.51), whereas there was a higher intradural invasion score in the LM8 implantation 12 weeks after irradiation group than the 12 weeks after nonirradiation group (3 of 10 Grade 0, 3 of 10 Grade 1 and 4 of 10 Grade 2 versus 8 of 10 Grade 0 and 2 of 10 Grade 1; p = 0.04). Interobserver reliability of assessing intradural tumor invasion grades in the LM8-implanted group was 0.93. In the microstructural analysis of the dura mater using SEM, irradiated mice had small defects on the dural surface at low magnification and degeneration of collagen fibers at high magnification. The median (range) number of defects on the dural surface per image in the irradiated mice was larger than that of nonirradiated mice (2 [1 to 3] versus 0; difference of medians, 2/image; p = 0.002) and the median size of defects was 60 µm (30 to 80). Interobserver reliability of assessing number of defects on the dural surface was 1.00. TEM revealed that nonirradiated mice demonstrated well-organized, multilayer structures, while irradiated mice demonstrated irregularly layered structures at low magnification. At high magnification, well-ordered cross-sections of collagen fibers were observed in the nonirradiated mice. However, disordered alignment of collagen fibers was observed in irradiated mice. CONCLUSION: Intradural tumor invasion and disruptions of the dural microstructure were observed in the meninges of mice after irradiation, indicating radiation-induced disruption of the meningeal barrier. CLINICAL RELEVANCE: We conclude that in this form of delivery, radiation is associated with disruption of the dural meningeal barrier, indicating a need to consider methods to avoid or limit Postradiation tumor relapse and spinal cord compression when treating spinal metastases so that patients do not experience intradural tumor invasion. Surgeons should be aware of the potential for intradural tumor invasion when they perform post-irradiation spinal surgery to minimize the risks for intraoperative dural injury and spinal cord injury. Further research in patients with irradiated spinal metastases is necessary to confirm that the same findings are observed in humans and to seek irradiation methods that prevent or minimize the disruption of meningeal barrier function.

Intensity-modulated radiation therapy administered to a previously irradiated spine is effective and well-tolerated.

PURPOSE: This study sought to discern the clinical outcomes of intensity-modulated radiation therapy (IMRT) administered to the spine in patients who had undergone previous radiotherapy. METHODS: A total of 81 sites of 74 patients who underwent previous radiotherapy administered to the spine or peri-spine and subsequently received IMRT for the spine were analyzed in this study. The prescribed dose of 80 Gy in a biologically effective dose (BED) of α/ß = 10 (BED10) was set as the planning target volume. The constraint for the spinal cord and cauda equine was D0.1 cc ≤ 100 Gy and ≤ 150 Gy of BED for re-irradiation alone and the total irradiation dose, respectively. RESULTS: The median follow-up period was 10.1 (0.9-92.1) months after re-irradiation, while the median interval from the last day of the previous radiotherapy to the time of re-irradiation was 15.6 (0.4-210.1) months. Separately, the median prescript dose of re-irradiation was 78.0 (28.0-104.9) of BED10. The median survival time in this study was 13.9 months, with 1-, 3-, and 5-year overall survival rates of 53.7%, 29.3%, and 26.6%, respectively. The 1-, 3-, and 5-year local control rates were 90.8%, 84.0%, and 84.0%, respectively. Neurotoxicity was observed in two of 72 treatments (2.8%) assessed after re-irradiation. CONCLUSION: Re-irradiation for the spine using IMRT seems well-tolerated. Definitive re-irradiation can be a feasible treatment option in patients with the potential for a good prognosis.

Effects of photobiomodulation combined with MSCs transplantation on the repair of spinal cord injury in rat.

Stem cell transplantation has shown promising regenerative effects against neural injury, and photobiomodulation (PBM) can aid tissue recovery. This study aims to evaluate the therapeutic effect of human umbilical cord mesenchymal stem cells (hUCMSCs) and laser alone or combined on spinal cord injury (SCI). The animals were divided into SCI, hUCMSCs, laser treatment (LASER) and combination treatment (hUCMSCs + LASER) groups. Cell-enriched grafts of hUCMSCs (1 × 106 cells/ml) were injected at the site of antecedent trauma in SCI model rats. A 2 cm2 damaged area was irradiated with 630 nm laser at 100 mW/cm2 power for 20 min. Locomotion was evaluated using Basso-Beattie-Bresnahan (BBB) scores, and neurofilament repair were monitored by histological staining and diffusion tensor imaging (DTI). First, after SCI, the motor function of each group was restored with different degrees, the combination treatment significantly increased the BBB scores compared to either monotherapy. In addition, Nissl bodies were more numerous, and the nerve fibers were longer and thicker in the combination treatment group. Consistent with this, the in situ expression of NF-200 and glial fibrillary acidic protein in the damaged area was the highest in the combination treatment group. Finally, DTI showed that the combination therapy optimally improved neurofilament structure and arrangement. These results may show that the combination of PBM and hUCMSCs transplantation is a feasible strategy for reducing secondary damage and promoting functional recovery following SCI.

[Radiotherapy and spinal toxicity: News and perspectives]. / Radiothérapie et toxicité médullaire : actualités et perspectives.

Radiation-induced myelopathy is a devastating late effect of radiotherapy. Fortunately, this late effect is exceptional. The clinical presentation of radiation myelopathy is aspecific, typically occurring between 6 to 24 months after radiotherapy, and radiation-induced myelopathy remains a diagnosis of exclusion. Magnetic resonance imaging is the most commonly used imaging tool. Radiation oncologists must be extremely cautious to the spinal cord dose, particularly in stereotactic radiotherapy and reirradiation. Conventionally, a maximum dose of 50Gy is tolerated in normofractionated radiotherapy (1.8 to 2Gy per fraction). Repeat radiotherapies lead to consider cumulative doses above this recommendation to offer individualized reirradiation. Several factors increase the risk of radiation-induced myelopathy, such as concomitant or neurotoxic chemotherapy. The development of predictive algorithms to prevent the risk of radiation-induced myelopathy is promising. However, radiotherapy prescription should be cautious, regarding to ALARA principle (as low as reasonably achievable). As the advent of immunotherapy has improved patient survival data and the concept of oligometastatic cancer is increasing in daily practice, stereotactic treatments and reirradiations will be increasingly frequent indications. Predict the risk of radiation-induced myelopathy is therefore a major issue in the following years, and remains a daily challenge for radiation oncologists.

Exosomes and exosomal microRNA in non-targeted radiation bystander and abscopal effects in the central nervous system.

Localized cranial radiotherapy is a dominant treatment for brain cancers. After being subjected to radiation, the central nervous system (CNS) exhibits targeted effects as well as non-targeted radiation bystander effects (RIBE) and abscopal effects (RIAE). Radiation-induced targeted effects in the CNS include autophagy and various changes in tumor cells due to radiation sensitivity, which can be regulated by microRNAs. Non-targeted radiation effects are mainly induced by gap junctional communication between cells, exosomes containing microRNAs can be transduced by intracellular endocytosis to regulate RIBE and RIAE. In this review, we discuss the involvement of microRNAs in radiation-induced targeted effects, as well as exosomes and/or exosomal microRNAs in non-targeted radiation effects in the CNS. As a target pathway, we also discuss the Akt pathway which is regulated by microRNAs, exosomes, and/or exosomal microRNAs in radiation-induced targeted effects and RIBE in CNS tumor cells. As the CNS-derived exosomes can cross the blood-brain-barrier (BBB) into the bloodstream and be isolated from peripheral blood, exosomes and exosomal microRNAs can emerge as promising minimally invasive biomarkers and therapeutic targets for radiation-induced targeted and non-targeted effects in the CNS.