Carbon ion radiotherapy boost in the treatment of glioblastoma: a randomized phase I/III clinical trial

CCNA2 and NEK2 regulate glioblastoma progression by targeting the cell cycle

Glioblastoma (GBM) is characterized by significant heterogeneity, leading to poor survival outcomes for patients, despite the implementation of comprehensive treatment strategies. The roles of cyclin A2 (CCNA2) and NIMA related kinase 2 (NEK2) have been extensively studied in numerous cancers, but their specific functions in GBM remain to be elucidated. The present study aimed to investigate the potential molecular mechanisms of CCNA2 and NEK2 in GBM. CCNA2 and NEK2 expression and prognosis in glioma were evaluated by bioinformatics methods. In addition, the distribution of CCNA2 and NEK2 expression in GBM subsets was determined using pseudo-time analysis and tricycle position of single-cell sequencing. Gene Expression Omnibus and Kyoto Encyclopedia of Genes and Genome databases were employed and enrichment analyses were conducted to investigate potential signaling pathways in GBM subsets and a nomogram was established to predict 1-, 2- and 3-year overall survival probability in GBM. CCNA2 and NEK2 expression levels were further validated by western blot analysis and immunohistochemical staining in GBM samples. High expression of CCNA2 and NEK2 in glioma indicates poor clinical outcomes. Single-cell sequencing of GBM revealed that these genes were upregulated in a subset of positive neural progenitor cells (P-NPCs), which showed significant proliferation and progression properties and may activate G2M checkpoint pathways. A comprehensive nomogram predicts 1-, 2- and 3-year overall survival probability in GBM by considering P-NPCs, age, chemotherapy and radiotherapy scores. CCNA2 and NEK2 regulate glioblastoma progression by targeting the cell cycle, thus indicating the potential of novel therapy directed to CCNA2 and NEK2 in GBM.

Review of Recent Improvements in Carbon Ion Radiation Therapy in the Treatment of Glioblastoma

Purpose

This article provides an overview of the physical and biologic properties of carbon ions, followed by an examination of the latest clinical outcomes in patients with glioma who have received carbon ion radiation therapy.

Methods and Materials

According to thee articles that have been reviewed, glioma represents the predominant form of neoplastic growth in the brain, accounting for approximately 51% of all malignancies affecting the nervous system. Currently, high-grade glioma, specifically glioblastoma, comprises 15% of cases and is associated with a high mortality rate. The development of novel drugs for the treatment of high-grade tumors has been impeded by various factors, such as the blood-brain barrier and tumor heterogeneity, despite numerous endeavors. According to the definition of tumor grade established by the World Health Organization, the conventional treatment involves surgical resection followed by adjuvant radiation and chemotherapy. Despite numerous attempts in photon radiation therapy to apply the highest possible dose to the tumor site while minimizing damage to healthy tissue, there has been no success in increasing patient survival. The primary cause of resistance to conventional radiation therapy methods, namely x-ray and gamma-ray, is attributed to the survival of radio-resistant glioma stem cells, which have the potential to trigger a recurrence of tumors. Particle beams, such as protons and carbon ions, can deposit the highest dose to a confined region, thus offering a more accurate dose distribution compared with photon beams.

Results

Carbon ions exhibit higher linear energy transfer and relative biologic effectiveness compared with photons, potentially enabling them to overcome radio-resistant tumor cells.

Conclusions

Therefore, it can be hypothesized that carbon ion radiation therapy may show superior efficacy in destroying neoplastic cells with reduced negative outcomes compared with x-ray radiation therapy.

Carbon Ions for Hypoxic Tumors: Are We Making the Most of Them?

Hypoxia, which is associated with abnormal vessel growth, is a characteristic feature of many solid tumors that increases their metastatic potential and resistance to radiotherapy. Carbon-ion radiation therapy, either alone or in combination with other treatments, is one of the most promising treatments for hypoxic tumors because the oxygen enhancement ratio decreases with increasing particle LET. Nevertheless, current clinical practice does not yet fully benefit from the use of carbon ions to tackle hypoxia. Here, we provide an overview of the existing experimental and clinical evidence supporting the efficacy of C-ion radiotherapy in overcoming hypoxia-induced radioresistance, followed by a discussion of the strategies proposed to enhance it, including different approaches to maximize LET in the tumors.

Carbon-ion radiotherapy boost with standard dose proton radiation for incomplete-resected high-grade glioma: a phase 1 study

Background

To investigate the maximal tolerated dose (MTD) of a carbon-ion radiotherapy (CIRT) boost prior to standard dose proton radiotherapy (PRT) for newly diagnosed glioblastoma (GBM) and anaplastic astrocytoma (AA) patients with residual lesion after resection.

Methods

In total, 18 patients with high-grade glioma (HGG) (16 with GBM and 2 with AA) were enrolled in a prospective 3×3 design phase 1 trial. We investigated four dose-levels of CIRT boost [9 (starting level), 12, 15, and 18 Gy relative biological effectiveness (RBE)] delivered in three equal fractions prior to the standard dose PRT (60 Gy RBE in 30 fractions). Concurrent temozolomide (TMZ) was not provided during the CIRT boost but was initiated on the first day of PRT. Acute and late toxicities were scored based on the Common Terminology Criteria for Adverse Events (CTCAE, v 4.03). Dose-limiting toxicities (DLTs) were defined as radiation-induced severe toxicities (≥ grade 3).

Results

With a median follow-up of 17.9 months, no severe (≥ grade 3) acute or late toxicities were observed in patients treated with the first three dose levels (CIRT boost doses of 9, 12, 15 Gy RBE). Severe late toxicity (grade 3 radiation necrosis) was observed in the first patient treated with the 18 Gy RBE CIRT boost level. Therefore, this trial was terminated and the MTD of the induction CIRT boost was determined at 15 Gy RBE in 3 fractions. At the time of this analysis, both patients with AA were alive without disease progression. The progression-free survival (PFS) and overall survival (OS) for GBM at 12 months were 50.6% and 78.6%, respectively.

Conclusions

Particle beam radiotherapy consisting of a CIRT boost of 15 Gy RBE (in 3 fractions) following standard dose PRT (60 Gy RBE in 30 fractions), and used in conjunction with TMZ, is safe and potentially effective for patients with HGG.

Perfusion MR prior to radiotherapy is a strong predictor of survival in high-grade gliomas after proton and carbon ion radiotherapy

Background

To assess the survival predictability of perfusion magnetic resonance imaging (MRI) by the normalized cerebral blood volume (nCBV) prior to particle beam radiotherapy (PBRT) in high-grade glioma (HGG) patients underwent particle therapy.

Methods

The study retrieved dynamic susceptibility contrast MRI acquired prior to PBRT between 6/2015 and 3/2019 in 45 patients with HGG. Maximum nCBV (nCBVmax) within or adjacent to surgical/tumor bed was measured using 'hot-spot' method. The predictive values of nCBVmax for progression-free survival (PFS) and overall survival (OS) were assessed in univariate Kaplan-Meier curve and multivariate Cox proportional hazards (CPH) models. Nomograms based on CPH results were constructed to individualize the predicted probability of OS and PFS.

Results

The Kaplan-Meier curves and all CPH models based on nCBVmax as continuous variable (nCBVmax-C), group by cut-off derived from median value and Youden-index method showed that nCBVmax prior to radiotherapy was a strong predictor for both PFS and OS in HGG patients who underwent PBRT. Nomograms built on CPH models showed similar excellent performance in both discrimination and calibration.

Conclusions

Perfusion imaging prior to PBRT is a strong predictor of survival in HGG. Novel perfusion MR-based nomogram with prospective validation could potentially be formally used in future clinical practice to individualize survival probability.

Unraveling Mitochondrial Determinants of Tumor Response to Radiation Therapy

Radiotherapy represents a highly targeted and efficient treatment choice in many cancer types, both with curative and palliative intents. Nevertheless, radioresistance, consisting in the adaptive response of the tumor to radiation-induced damage, represents a major clinical problem. A growing body of the literature suggests that mechanisms related to mitochondrial changes and metabolic remodeling might play a major role in radioresistance development. In this work, the main contributors to the acquired cellular radioresistance and their relation with mitochondrial changes in terms of reactive oxygen species, hypoxia, and epigenetic alterations have been discussed. We focused on recent findings pointing to a major role of mitochondria in response to radiotherapy, along with their implication in the mechanisms underlying radioresistance and radiosensitivity, and briefly summarized some of the recently proposed mitochondria-targeting strategies to overcome the radioresistant phenotype in cancer.

Roadmap: helium ion therapy

Helium ion beam therapy for the treatment of cancer was one of several developed and studied particle treatments in the 1950s, leading to clinical trials beginning in 1975 at the Lawrence Berkeley National Laboratory. The trial shutdown was followed by decades of research and clinical silence on the topic while proton and carbon ion therapy made debuts at research facilities and academic hospitals worldwide. The lack of progression in understanding the principle facets of helium ion beam therapy in terms of physics, biological and clinical findings persists today, mainly attributable to its highly limited availability. Despite this major setback, there is an increasing focus on evaluating and establishing clinical and research programs using helium ion beams, with both therapy and imaging initiatives to supplement the clinical palette of radiotherapy in the treatment of aggressive disease and sensitive clinical cases. Moreover, due its intermediate physical and radio-biological properties between proton and carbon ion beams, helium ions may provide a streamlined economic steppingstone towards an era of widespread use of different particle species in light and heavy ion therapy. With respect to the clinical proton beams, helium ions exhibit superior physical properties such as reduced lateral scattering and range straggling with higher relative biological effectiveness (RBE) and dose-weighted linear energy transfer (LET_d) ranging from ∼4 keVμm^-1to ∼40 keVμm^-1. In the frame of heavy ion therapy using carbon, oxygen or neon ions, where LET_dincreases beyond 100 keVμm^-1, helium ions exhibit similar physical attributes such as a sharp lateral penumbra, however, with reduced radio-biological uncertainties and without potentially spoiling dose distributions due to excess fragmentation of heavier ion beams, particularly for higher penetration depths. This roadmap presents an overview of the current state-of-the-art and future directions of helium ion therapy: understanding physics and improving modeling, understanding biology and improving modeling, imaging techniques using helium ions and refining and establishing clinical approaches and aims from learned experience with protons. These topics are organized and presented into three main sections, outlining current and future tasks in establishing clinical and research programs using helium ion beams-A. Physics B. Biological and C. Clinical Perspectives.

A randomized controlled phase III study comparing hadrontherapy with carbon ions versus conventional radiotherapy - including photon and proton therapy - for the treatment of radioresistant tumors: the ETOILE trial

BACKGROUND

Some cancers such as sarcomas (bone and soft tissue sarcomas) and adenoid cystic carcinomas are considered as radioresistant to low linear energy transfer radiation (including photons and protons) and may therefore beneficiate from a carbon ion therapy. Despite encouraging results obtained in phase I/II trials compared to historical data with photons, the spread of carbon ions has been limited mainly because of the absence of randomized medical data. The French health authorities stressed the importance of having randomized data for carbon ion therapy.

METHODS

The ETOILE study is a multicenter prospective randomized phase III trial comparing carbon ion therapy to either advanced photon or proton radiotherapy for inoperable or macroscopically incompletely resected (R2) radioresistant cancers including sarcomas and adenoid cystic carcinomas. In the experimental arm, carbon ion therapy will be performed at the National Center for Oncological Hadrontherapy (CNAO) in Pavia, Italy. In the control arm, photon or proton radiotherapy will be carried out in referent centers in France. The primary endpoint is progression-free survival (PFS). Secondary endpoints are overall survival and local control, toxicity profile, and quality of life. In addition, a prospective health-economic study and a radiobiological analysis will be conducted. To demonstrate an absolute improvement in the 5-year PFS rate of 20% in favor of carbon ion therapy, 250 patients have to be included in the study.

DISCUSSION

So far, no clinical study of phase III has demonstrated the superiority of carbon ion therapy compared to conventional radiotherapy, including proton therapy, for the treatment of radioresistant tumors.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT02838602 . Date of registration: July 20, 2016. The posted information will be updated as needed to reflect protocol amendments and study progress.

Flourish of Proton and Carbon Ion Radiotherapy in China

Proton and heavy ion therapy offer superior relative biological effectiveness (RBE) in the treatment of deep-seated tumors compared with conventional photon radiotherapy due to its Bragg-peak feature of energy deposition in organs. Many proton and carbon ion therapy centers are active all over the world. At present, five particle radiotherapy institutes have been built and are receiving patient in China, mainly including Wanjie Proton Therapy Center (WPTC), Shanghai Proton Heavy Ion Center (SPHIC), Heavy Ion Cancer Treatment Center (HIMM), Chang Gung Memorial Hospital (CGMH), and Ruijin Hospital affiliated with Jiao Tong University. Many cancer patients have benefited from ion therapy, showing unique advantages over surgery and chemotherapy. By the end of 2020, nearly 8,000 patients had been treated with proton, carbon ion or carbon ion combined with proton therapy. So far, there is no systemic review for proton and carbon ion therapy facility and clinical outcome in China. We reviewed the development of proton and heavy ion therapy, as well as providing the representative clinical data and future directions for particle therapy in China. It has important guiding significance for the design and construction of new particle therapy center and patients’ choice of treatment equipment.

Radiotherapy for glioblastoma: clinical issues and nanotechnology strategies

Glioblastoma multiforme (GBM) is the most common primary brain cancer in adults with poor prognosis. Despite the current state of knowledge on its genetic characteristics, relatively little progress has been made in improving the treatment of patients with this fatal disease. Radiotherapy (RT) has been identified as a crucial treatment for GBM following surgical resection to improve both local control and survival. Unfortunately, radiotherapy resistance is frequently observed in GBM patients, which is the major reason for the high mortality rate of cancer patients. Radioresistance of GBM is often multifactorial and heterogeneous, and associated with the recurrence of GBM after surgery. Nanotechnology has gained increasing attention and has already been investigated for optimization of radiosensitization due to the unique properties of nanobiomaterials, such as photoelectric decay characteristics or potential as carriers for drug delivery to the central nervous system. A large body of preclinical data has accumulated over the past several years, in which nanotechnology-based strategies exhibit promising potential to enhance the radiosensitivity of GBM, both in cellular and animal models. In this review, we summarize the mechanisms of GBM radioresistance, including tumor cell-intrinsic factors as well as tumor microenvironment (TME). We further discuss current nano-biotechnology-based radiosensitizer in the treatment of GBM, summarize the latest findings, highlight challenges, and put forward prospects for the future of nano-radiosensitizers. These data suggest that nanotechnology has the potential to address many of the clinical challenges and nanobiomaterials would become promising next-generation radiotherapy sensitizers for GBM treatment.

Carbon ion radiotherapy boosts anti-tumour immune responses by inhibiting myeloid-derived suppressor cells in melanoma-bearing mice

Numerous studies have shown that carbon ion radiotherapy (CIRT) induces anti-cancer immune responses in melanoma patients, yet the mechanism remains elusive. The abundance of myeloid-derived suppressor cells (MDSC) in the tumour microenvironment is associated with therapeutic efficacy and disease outcome. This study analysed the changes in the immune contexture in response to the carbon ion treatment. The murine melanoma B16, MelanA, and S91 tumour models were established in syngeneic immunocompetent mice. Then, the tumours were irradiated with carbon ion beams, and flow cytometry was utilised to observe the immune contexture changes in the bone marrow, peripheral blood, spleen, and tumours. The immune infiltrates in the tumour tissues were further assessed using haematoxylin/eosin staining and immunohistochemistry. The immunoblot detected the expression of proteins associated with the JAK/STAT signalling pathway. The secretion of immune-related cytokines was examined using ELISA. Compared to conventional radiotherapy, particle beams have distinct advantages in cancer therapy. Here, the use of carbon ion beams (5 GyE) for melanoma-bearing mice was found to reduce the population of MDSC in the bone marrow, peripheral blood, and spleen of the animals via a JAK2/STAT3-dependent mechanism. The percentage of CD3⁺, CD4⁺, CD8⁺ T cells, macrophages, and natural killer cells increased after radiation, resulting in reduced tumour growth and prolonged overall survival in the three different mouse models of melanoma. This study, therefore, substantiated that CIRT boosts anti-tumour immune responses via the inhibition of MDSC.

Role of Mitochondria in Radiation Responses: Epigenetic, Metabolic, and Signaling Impacts

Until recently, radiation effects have been considered to be mainly due to nuclear DNA damage and their management by repair mechanisms. However, molecular biology studies reveal that the outcomes of exposures to ionizing radiation (IR) highly depend on activation and regulation through other molecular components of organelles that determine cell survival and proliferation capacities. As typical epigenetic-regulated organelles and central power stations of cells, mitochondria play an important pivotal role in those responses. They direct cellular metabolism, energy supply and homeostasis as well as radiation-induced signaling, cell death, and immunological responses. This review is focused on how energy, dose and quality of IR affect mitochondria-dependent epigenetic and functional control at the cellular and tissue level. Low-dose radiation effects on mitochondria appear to be associated with epigenetic and non-targeted effects involved in genomic instability and adaptive responses, whereas high-dose radiation effects (>1 Gy) concern therapeutic effects of radiation and long-term outcomes involving mitochondria-mediated innate and adaptive immune responses. Both effects depend on radiation quality. For example, the increased efficacy of high linear energy transfer particle radiotherapy, e.g., C-ion radiotherapy, relies on the reduction of anastasis, enhanced mitochondria-mediated apoptosis and immunogenic (antitumor) responses.

SP1 transcriptionally activates NLRP6 inflammasome and induces immune evasion and radioresistance in glioma cells

Glioma accounts for approximately 80% of all malignant brain tumors. This study aimed to investigate the interaction between specificity protein 1 (SP1) and NLR family pyrin domain containing 6 (NLRP6) and their roles in the activity of glioma cells. Differentially expressed genes in glioma were identified using transcriptome analysis tools, and a protein-protein-interaction network was performed based on the DEGs. SP1 and NLRP6 were abundantly expressed in glioma cells and indicated unfavorable prognosis of patients according to the GEO datasets. SP1could bind to the promoter of NLRP6 and induce its transcriptional activity. Downregulation of SP1 reduced proliferation, migration and invasion of glioma U87 cells in vitro as well as tumorigenesis in vivo. The malignancy of cells was restored after NLRP6 upregulation. Downregulation of SP1 in glioma cells also increased proliferation of CD8+ T cells and the immune activity in U87 cells, and it reduced the radioresistance of U87 cells. However, the immune evasion and radioresistance of glioma cells were restored upon NLRP6 upregulation. NLRP6 mediated the innate immune pathway through an ASC/caspase-1/IL-1β axis. To conclude, this study suggested that SP1 interacts with NLRP6 inflammasome to enhance malignant behaviors, immune evasion and radioresistance in glioma cells.

Carbon-ion radiotherapy in osteosarcoma of the mandible: a case report

Carbon-ion radiotherapy (CIRT) is on the rise as a treatment choice for malignant tumor. Compared to conventional radiotherapy, particle beams have different physical and biological properties. Particle beam provides a low entry dose, deposits most of the energy at the endpoint of the flight path, and forms an asymptotic dose peak (the "Bragg peak"). Compared to protons, carbon with its larger mass decreases beam scattering, resulting in a sharper dose distribution border. We report a 50-year-old male who underwent CIRT without surgical resection on osteosarcoma of the mandible. After CIRT, the patient's pain was gone, and the malignant mass remained stable with accompanying necrosis. Nine months later, however, magnetic resonance imaging demonstrated progression of the left mandibular osteosarcoma with pulmonary metastases. After multidisciplinary discussion, concurrent chemoradiotherapy was conducted. While necrotic bone segments came out of the mandible during subsequent periodic outpatient visits, the tumor itself was stable. Thirty months after his first visit and diagnosis, the patient is waiting for chemotherapy. Although CIRT is superior in treating radioresistant hypoxic disease, CIRT is in its infancy, so care must be taken for its indications and complications.

MDM2/X Inhibitors as Radiosensitizers for Glioblastoma Targeted Therapy

Inhibition of the MDM2/X-p53 interaction is recognized as a potential anti-cancer strategy, including the treatment of glioblastoma (GB). In response to cellular stressors, such as DNA damage, the tumor suppression protein p53 is activated and responds by mediating cellular damage through DNA repair, cell cycle arrest and apoptosis. Hence, p53 activation plays a central role in cell survival and the effectiveness of cancer therapies. Alterations and reduced activity of p53 occur in 25-30% of primary GB tumors, but this number increases drastically to 60-70% in secondary GB. As a result, reactivating p53 is suggested as a treatment strategy, either by using targeted molecules to convert the mutant p53 back to its wild type form or by using MDM2 and MDMX (also known as MDM4) inhibitors. MDM2 down regulates p53 activity via ubiquitin-dependent degradation and is amplified or overexpressed in 14% of GB cases. Thus, suppression of MDM2 offers an opportunity for urgently needed new therapeutic interventions for GB. Numerous small molecule MDM2 inhibitors are currently undergoing clinical evaluation, either as monotherapy or in combination with chemotherapy and/or other targeted agents. In addition, considering the major role of both p53 and MDM2 in the downstream signaling response to radiation-induced DNA damage, the combination of MDM2 inhibitors with radiation may offer a valuable therapeutic radiosensitizing approach for GB therapy. This review covers the role of MDM2/X in cancer and more specifically in GB, followed by the rationale for the potential radiosensitizing effect of MDM2 inhibition. Finally, the current status of MDM2/X inhibition and p53 activation for the treatment of GB is given.

Application of New Radiosensitizer Based on Nano-Biotechnology in the Treatment of Glioma

Glioma is the most common intracranial malignant tumor, and its specific pathogenesis has been unclear, which has always been an unresolved clinical problem due to the limited therapeutic window of glioma. As we all know, surgical resection, chemotherapy, and radiotherapy are the main treatment methods for glioma. With the development of clinical trials and traditional treatment techniques, radiotherapy for glioma has increasingly exposed defects in the treatment effect. In order to improve the bottleneck of radiotherapy for glioma, people have done a lot of work; among this, nano-radiosensitizers have offered a novel and potential treatment method. Compared with conventional radiotherapy, nanotechnology can overcome the blood–brain barrier and improve the sensitivity of glioma to radiotherapy. This paper focuses on the research progress of nano-radiosensitizers in radiotherapy for glioma.

The Emerging Potential of Multi-Ion Radiotherapy

Research into high linear energy transfer (LET) radiotherapy now spans over half a century, beginning with helium and deuteron treatment in 1952 and today ranging from fast neutrons to carbon-ions. Owing to pioneering work initially in the United States and thereafter in Germany and Japan, increasing focus is on the carbon-ion beam: 12 centers are in operation, with five under construction and three in planning. While the carbon-ion beam has demonstrated unique and promising suitability in laboratory and clinical trials toward the hypofractionated treatment of hypoxic and/or radioresistant cancer, substantial developmental potential remains. Perhaps most notable is the ability to paint LET in a tumor, theoretically better focusing damage delivery within the most resistant areas. However, the technique may be limited in practice by the physical properties of the beams themselves. A heavy-ion synchrotron may provide irradiation with multiple heavy-ions: carbon, helium, and oxygen are prime candidates. Each ion varies in LET distribution, and so a methodology combining the use of multiple ions into a uniform LET distribution within a tumor may allow for even greater treatment potential in radioresistant cancer.

A Ki-67 Index to Predict Treatment Response to the Capecitabine/Temozolomide Regimen in Neuroendocrine Neoplasms: A Retrospective Multicenter Study

OBJECTIVE

The efficacy of the capecitabine/temozolomide (CAPTEM) regimen has been demonstrated in metastatic neuroendocrine neoplasms (NENs), but because of varying response rates among the patients, biomarkers to predict its response are greatly needed. Here, we investigated the clinical utility of a Ki-67 index to predict the CAPTEM regimen objective responses and select patients who could benefit from this regimen.

METHODS

Metastatic NENs patients treated with the CAPTEM regimen from 4 high-volume medical centers were selected and grouped in a training and validation cohort. The classification and regression tree (CART) was generated to identify the optimal threshold of Ki-67 for stratifying the patients into different Ki-67 range groups based on their response to the CAPTEM regimen.

RESULTS AND CONCLUSIONS

The overall response rate (ORR) and disease control rate of the entire cohort (N = 151) were 26.5 and 76.2%, respectively, with a median progression-free survival (PFS) of 12.0 months. CART analysis showed that patients in the Ki-67 range group 10-40% demonstrated a significantly higher ORR than those in Ki-67 >40 and <10% groups (p < 0.001 in the training cohort and p = 0.036 in the validation cohort). Response to the CAPTEM regimen was not influenced by the expression of O6-methylguanine-DNA methyltransferase or primary tumor location. Multivariate analysis identified the Ki-67 index as the only independent prognostic factor for overall survival (p = 0.031) and PFS (p = 0.006). The proposed Ki-67 index was externally validated and could be used to clinically identify suitable metastatic NENs patients who could achieve an optimal cytoreduction using the CAPTEM regimen.

A Comparison Study of Machine Learning (Random Survival Forest) and Classic Statistic (Cox Proportional Hazards) for Predicting Progression in High-Grade Glioma after Proton and Carbon Ion Radiotherapy

Background

Machine learning (ML) algorithms are increasingly explored in glioma prognostication. Random survival forest (RSF) is a common ML approach in analyzing time-to-event survival data. However, it is controversial which method between RSF and traditional cornerstone method Cox proportional hazards (CPH) is better fitted. The purpose of this study was to compare RSF and CPH in predicting tumor progression of high-grade glioma (HGG) after particle beam radiotherapy (PBRT).

Methods

The study enrolled 82 consecutive HGG patients who were treated with PBRT at Shanghai Proton and Heavy Ion Center between 6/2015 and 11/2019. The entire cohort was split into the training and testing set in an 80/20 ratio. Ten variables from patient-related, tumor-related and treatment-related information were utilized for developing CPH and RSF for predicting progression-free survival (PFS). The model performance was compared in concordance index (C-index) for discrimination (accuracy), brier score (BS) for calibration (precision) and variable importance for interpretability.

Results

The CPH model demonstrated a better performance in terms of integrated C-index (62.9%) and BS (0.159) compared to RSF model (C-index = 61.1%, BS = 0.174). In the context of variable importance, CPH model indicated that age (P = 0.024), WHO grade (P = 0.020), IDH gene (P = 0.019), and MGMT promoter status (P = 0.040) were significantly correlated with PFS in the univariate analysis; multivariate analysis showed that age (P = 0.041), surgical completeness (P = 0.084), IDH gene (P = 0.057), and MGMT promoter (P = 0.092) had a significant or trend toward the relation with PFS. RSF showed that merely IDH and age were of positive importance for predicting PFS. A final nomogram was developed to predict tumor progression at the individual level based on CPH model.

Conclusions

In a relatively small dataset with HGG patients treated with PBRT, CPH outperformed RSF for predicting tumor progression. A comprehensive criterion with accuracy, precision, and interpretability is recommended in evaluating ML prognostication approaches for clinical deployment.

Impact of Hypoxia on Carbon Ion Therapy in Glioblastoma Cells: Modulation by LET and Hypoxia-Dependent Genes

Tumor hypoxia is known to limit the efficacy of ionizing radiations, a concept called oxygen enhancement ratio (OER). OER depends on physical factors such as pO₂ and linear energy transfer (LET). Biological pathways, such as the hypoxia-inducible transcription factors (HIF), might also modulate the influence of LET on OER. Glioblastoma (GB) is resistant to low-LET radiation (X-rays), due in part to the hypoxic environment in this brain tumor. Here, we aim to evaluate in vitro whether high-LET particles, especially carbon ion radiotherapy (CIRT), can overcome the contribution of hypoxia to radioresistance, and whether HIF-dependent genes, such as erythropoietin (EPO), influence GB sensitivity to CIRT. Hypoxia-induced radioresistance was studied in two human GB cells (U251, GL15) exposed to X-rays or to carbon ion beams with various LET (28, 50, 100 keV/µm), and in genetically-modified GB cells with downregulated EPO signaling. Cell survival, radiobiological parameters, cell cycle, and ERK activation were assessed under those conditions. The results demonstrate that, although CIRT is more efficient than X-rays in GB cells, hypoxia can limit CIRT efficacy in a cell-type manner that may involve differences in ERK activation. Using high-LET carbon beams, or targeting hypoxia-dependent genes such as EPO might reduce the effects of hypoxia.

Different Mechanisms Underlie the Metabolic Response of GBM Stem-Like Cells to Ionizing Radiation: Biological and MRS Studies on Effects of Photons and Carbon Ions

Glioblastoma multiforme (GBM) is a malignant primary brain tumor with very poor prognosis, high recurrence rate, and failure of chemo-radiotherapy, mainly due to a small fraction of cells with stem-like properties (GSCs). To study the mechanisms of GSCs resistance to radiation, two GSC lines, named line #1 and line #83, with different metabolic patterns and clinical outcome, were irradiated with photon beams and carbon ions and assessed by ¹H Magnetic Resonance Spectroscopy (MRS). Both irradiation modalities induced early cytotoxic effects in line #1 with small effects on cell cycle, whereas a proliferative G2/M cytostatic block was observed in line #83. MR spectroscopy signals from mobile lipids (ML) increased in spectra of line #1 after photon and C-ion irradiation with effects on lipid unsaturation level, whereas no effects were detected in line #83 spectra. Gamma-Aminobutyric Acid (GABA), glutamic acid (glu) and Phosphocreatine (pCr) signals showed a significant variation only for line #1 after carbon ion irradiation. Glucose (glc) level and lactate (Lac) extrusion behaved differently in the two lines. Our findings suggest that the differences in irradiation response of GSCs #1 and #83 lines are likely attributable to their different metabolic fingerprint rather than to the different radiation types.

Particle radiation therapy in the management of malignant glioma: Early experience at the Shanghai Proton and Heavy Ion Center

Background

The objective of this study was to evaluate the outcomes of patients with high‐grade glioma who received treatment with particle radiotherapy.

Methods

Between June 2015 and October 2018, 50 consecutive and nonselected patients with glioblastoma multiforme (n = 34) or anaplastic glioma (n = 16) were treated at the Shanghai Proton and Heavy Ion Center. Twenty‐four patients received proton radiotherapy (at a dose of 60 gray‐equivalents in 30 daily fractions), and 26 patients received proton radiotherapy plus a carbon‐ion radiotherapy (CIRT) boost in various dose‐escalating schemes. All patients received temozolomide because of their age or their O‐6‐methylguanine‐DNA methyltransferase (MGMT) promoter methylation status. Progression‐free survival (PFS) and overall survival (OS) rates, as well as treatment‐induced toxicities, were analyzed.

Results

At a median follow‐up of 14.3 months (range, 4.8‐39.6 months), the 12‐month and 18‐month OS rates were 87.8% (95% CI, 77.6%‐98.0%) and 72.8% (95% CI, 56.7%‐88.9%), respectively, and the 12‐month and 18‐month PFS rates were 74.2% (95% CI, 60.9%‐87.5%) and 59.8% (95% CI, 43.1%‐76.5%), respectively. Univariate analyses revealed that age (>50 vs ≤50 years), World Health Organization grade (3 vs 4), and Karnofsky performance status (>80 vs ≤80) were significant prognosticators for OS, and IDH mutation and World Health Organization grade were significant for predicting PFS. Furthermore, MGMT promoter methylation, performance status, and age showed a trend toward predicting PFS. No significant predictive factors for PFS or OS were identified in multivariate analyses. Twenty‐nine patients experienced grade 1 treatment‐related acute adverse effects, and 11 developed grade 1 (n = 6) or grade 2 (n = 5) late adverse effect of radiation‐induced brain necrosis. No grade 3, 4, or 5 toxicities were observed.

Conclusions

Particle radiotherapy produced 18‐month OS and PFS rates of 72.8% and 59.8%, respectively, with acceptable adverse effects in patients with high‐grade glioma. Particle radiotherapy at a dose ≥60 gray‐equivalents appears to be safe and potentially effective.

Particle radiotherapy with concurrent temozolomide could potentially produce better outcomes than conventional radiotherapy plus temozolomide. Particle radiotherapy to a dose of ≥60 gray‐equivalents with concurrent temozolomide is safe for patients with high‐grade glioma.

Clustered DNA Double-Strand Breaks: Biological Effects and Relevance to Cancer Radiotherapy

Cells manage to survive, thrive, and divide with high accuracy despite the constant threat of DNA damage. Cells have evolved with several systems that efficiently repair spontaneous, isolated DNA lesions with a high degree of accuracy. Ionizing radiation and a few radiomimetic chemicals can produce clustered DNA damage comprising complex arrangements of single-strand damage and DNA double-strand breaks (DSBs). There is substantial evidence that clustered DNA damage is more mutagenic and cytotoxic than isolated damage. Radiation-induced clustered DNA damage has proven difficult to study because the spectrum of induced lesions is very complex, and lesions are randomly distributed throughout the genome. Nonetheless, it is fairly well-established that radiation-induced clustered DNA damage, including non-DSB and DSB clustered lesions, are poorly repaired or fail to repair, accounting for the greater mutagenic and cytotoxic effects of clustered lesions compared to isolated lesions. High linear energy transfer (LET) charged particle radiation is more cytotoxic per unit dose than low LET radiation because high LET radiation produces more clustered DNA damage. Studies with I-SceI nuclease demonstrate that nuclease-induced DSB clusters are also cytotoxic, indicating that this cytotoxicity is independent of radiogenic lesions, including single-strand lesions and chemically "dirty" DSB ends. The poor repair of clustered DSBs at least in part reflects inhibition of canonical NHEJ by short DNA fragments. This shifts repair toward HR and perhaps alternative NHEJ, and can result in chromothripsis-mediated genome instability or cell death. These principals are important for cancer treatment by low and high LET radiation.

Hadrontherapy Interactions in Molecular and Cellular Biology

The resistance of cancer cells to radiotherapy is a major issue in the curative treatment of cancer patients. This resistance can be intrinsic or acquired after irradiation and has various definitions, depending on the endpoint that is chosen in assessing the response to radiation. This phenomenon might be strengthened by the radiosensitivity of surrounding healthy tissues. Sensitive organs near the tumor that is to be treated can be affected by direct irradiation or experience nontargeted reactions, leading to early or late effects that disrupt the quality of life of patients. For several decades, new modalities of irradiation that involve accelerated particles have been available, such as proton therapy and carbon therapy, raising the possibility of specifically targeting the tumor volume. The goal of this review is to examine the up-to-date radiobiological and clinical aspects of hadrontherapy, a discipline that is maturing, with promising applications. We first describe the physical and biological advantages of particles and their application in cancer treatment. The contribution of the microenvironment and surrounding healthy tissues to tumor radioresistance is then discussed, in relation to imaging and accurate visualization of potentially resistant hypoxic areas using dedicated markers, to identify patients and tumors that could benefit from hadrontherapy over conventional irradiation. Finally, we consider combined treatment strategies to improve the particle therapy of radioresistant cancers.

Subventricular zone volumetric and dosimetric changes during postoperative brain tumor irradiation and its impact on overall survival

PURPOSE

The aim of this retrospective study was to investigate the relationship between the dose to the subventricular zone (SVZ) and overall survival (OS) of 41 patients with glioblastoma multiforme (GBM), who were treated with an adaptive approach involving repeated topometric CT and replanning at two-thirds (40 Gy) of their course of postoperative radiotherapy for planning of a 20 Gy boost.

METHODS

We examined changes in the ipsilateral lateral ventricle (LV) and SVZ (iLV and iSVZ), as well as in the contralateral LV and SVZ (cLV and cSVZ). We evaluated the volumetric changes on both planning CT scans (primary CT1 and secondary CT2). The survival of the GBM patients was analyzed using the Kaplan-Meier method; the multivariate Cox regression was also performed.

RESULTS

Median follow-up and OS were 34.5 months and 17.6 months, respectively. LV and SVZ structures exhibited significant volumetric changes on CT2, resulting in an increase of dose coverage. At a cut-off point of 58 Gy, a significant correlation was detected between the iSVZ2 mean dose and OS (27.8 vs 15.6 months, p = 0.048). In a multivariate analysis, GBM patients with a shorter time to postoperative chemoradiotherapy (<3.8 weeks), with good performance status (≥70%) and higher mean dose (≥58 Gy) to the iSVZ2 had significantly better OS.

CONCLUSIONS

Significant anatomical and dose distribution changes to the brain structures were observed, which have a relevant impact on the dose-effect relationship for GBM; therefore, involving the iSVZ in the target volume should be considered and adapted to the changes.

Comparison of the effects of photon, proton and carbon-ion radiation on the ecto-calreticulin exposure in various tumor cell lines

Background

Accumulating evidence suggested that radiotherapy can activate anti-tumor immune responses by triggering immunogenic cell death (ICD) of tumor cells. Calreticulin is regarded as one of the most important markers of ICD. The cell surface translocation of calreticulin (ecto-CRT) serves as an "eat me" signal for phagocytosis of dying cells, which plays a pivotal role in activating anti-tumor immunity. However, there is limited knowledge describing the effects of proton and carbon-ion radiation on ecto-CRT exposure. Hence, we investigated ecto-CRT exposure in multiple human carcinoma cell lines irradiated by proton and carbon-ion in comparison to photon.

Methods

This study examined four human cancer cell lines including A549 (lung adenocarcinoma), U251MG (glioma), Tca8113 (tongue squamous carcinoma), and CNE-2 (nasopharyngeal carcinoma). Cell lines were irradiated with photon, proton or carbon-ion at 0, 2, 4, 10 Gy (physical dose). The ecto-CRT exposure level was analyzed by flow cytometry at 12, 24, and 48 h post-irradiation. The median fluorescence intensity was calculated by FlowJo.

Results

All three types of radial beam increased ecto-CRT exposure of the 4 tumor cell lines in a time-dependent manner. Ecto-CRT exposure significantly elevated 1.5-2.4 times over 48 h post-irradiation compared with controls (P<0.05). Proton and photon increased ecto-CRT exposure with dose escalation. Photon and proton at 10 Gy increased the most ecto-CRT exposure (P<0.05), while carbon-ion increased most ecto-CRT exposure at 4 Gy rather than 10 or 2 Gy. When compared with iso-physical dose at 48 h post-irradiation, proton showed a similar effectiveness with photon. While carbon-ion has significantly stronger effects on increasing ecto-CRT than proton and photon at 2 and 4 Gy, but changed oppositely at 10 Gy (P<0.05).

Conclusions

All the three types of radiation can increase the ecto-CRT exposure in a time-dependent manner. Proton and photon radiation were equally effective in inducing ecto-CRT exposure, while carbon-ion revealed a different effectiveness in comparison to photon and proton.