Carbon ion radiotherapy in Japan: an assessment of 20 years of clinical experience

Dose Constraints in Carbon-Ion Radiation Therapy to Minimize the Risk of Pectoral Myositis

Purpose

Carbon-ion radiation therapy (C-ion RT) is an emerging nonsurgical treatment for early stage breast cancer, offering biological advantages such as high linear energy transfer (LET) and precise dose distribution. However, the risk of radiation-induced toxicity, particularly pectoral myositis, remains unclear. This study evaluates the relationship between RBE-weighted dose, LET, and pectoral myositis in patients receiving C-ion RT.

Patients and Methods

Fourteen patients with cT0-1N0M0 breast cancer were treated with C-ion RT (46-50 Gy [RBE]) in the prone position. Magnetic resonance imaging was performed pretreatment and at 3-month intervals post treatment to assess pectoral myositis. RBE-weighted dose-volume histograms and LET distributions were analyzed. Statistical comparisons between patients with and without pectoral myositis were conducted using chi-square and t-tests.

Results

Four of 14 patients (29%) developed pectoral myositis, all within 3 months of treatment. Higher RBE-weighted doses in small volumes of pectoralis major muscle were significantly associated with myositis (D2 cm3 >10 Gy [RBE], P = .014). The D0.1 cm3 to the pectoralis major muscle in patients without pectoral myositis was consistently below 33 Gy (RBE). However, LET distributions showed no significant correlation with myositis development.

Conclusion

This study is the first to evaluate pectoral myositis after C-ion RT for breast cancer. The findings suggest that high RBE-weighted doses in small muscle volumes increase the risk of myositis, while LET is not a significant factor. Establishing dose constraints for the pectoralis major muscle is crucial to minimize radiation-induced toxicity. Further studies with larger cohorts are needed to validate these results.

Carbon ion irradiation mobilizes antitumor immunity: from concept to the clinic

Carbon ion radiotherapy (CIRT), a type of particle therapy, is at the forefront of clinical oncology treatments due to its superior physical properties and biological performance. Although CIRT has demonstrated outstanding therapeutic outcomes in clinical settings, the biological mechanisms underpinning its effects, particularly its immunogenic potential and the superiority of its induced antitumor immune response compared to photon radiotherapy, remain areas of active investigation. This review summarizes the latest research progress on the mechanisms of antitumor immune responses triggered by CIRT and discusses preclinical and clinical studies related to combined CIRT and immunotherapy (CCIT). Against the backdrop of extensive research and significant clinical efficacy achieved by combining radiotherapy with immunotherapy, this review provides a theoretical foundation for a better understanding of the superior tumor cell-killing effects of CIRT and the underlying immunological mechanisms. Further insights into the factors affecting the efficacy, toxic effects, and developmental limitations of this combination therapy mode will be instrumental in guiding the conduction of CCIT studies.

A biological optimization method for carbon therapy via iterative Jacobian-based linearization

Objective.Carbon ion radiotherapy (CIRT) can provide higher biological effectiveness and cause more damage to cancer cells compared to photon or proton radiotherapy, especially for radio-resistant tumors. The optimization of biological dose is essential for CIRT, to achieve the desirable tumoricidal dose while mitigating biological damage to normal tissues and organs at risk (OAR). However, the biological optimization for CIRT is mathematically challenging, due to the nonlinear nature of biological dose model, which can lead to computational inaccuracy and inefficiency. This work will develop an accurate and efficient biological optimization method for CIRT.Approach.The proposed method is called iterative Jacobian-based linearization (IJL). In IJL, the biological dose is modeled as the product of the physical dose and relative biological effect, which is based on the linear-quadratic model via the local effect model in this work, and the optimization objective consists of dose-volume histogram based biological dose objectives within clinical target volume and OAR. The optimization algorithm for IJL is through iterative convex relaxation, in which the nonlinear biological dose is iteratively linearized using Jacobian-based approximations and the linear subproblems are solved using alternating direction method of multipliers. To compare with IJL, the limited-memory quasi-Newton (QN) method (limited-memory version) is developed that directly solves the same nonlinear biological optimization problem.Main results.Compared to the QN, IJL demonstrated superior plan accuracy, e.g. better OAR sparing with the reduction of biological dose in the CTV-surrounding volume (PTV1cm) to 89.7%, 95.0%, 88.3% for brain, lung, and abdomen, respectively; IJL also had higher computational efficiency, with approximately 1/10 the computational time per iteration and continuously decreasing objectives (while being stagnated for QN after certain number of iterations).Significance.A novel optimization algorithm, IJL, incorporating iterative linearization of biological dose, is proposed to accurately and efficiently solve the biological optimization problem for CIRT. It demonstrates superior plan accuracy and computational efficiency compared to the direct nonlinear QN optimization method.

Feasibility and safety of Taipei Veterans General Hospital Heavy Ion Therapy Center: The first carbon-ion irradiation facility in Taiwan

BACKGROUND

Unlike conventional photon radiotherapy, particle therapy has the advantage of dose distribution. Carbon-ion radiotherapy is also advantageous in terms of biological effectiveness and other radiobiological aspects. These benefits lead to a higher response probability for previously known radioresistant tumor types. Therefore, Taipei Veterans General Hospital, which is located in the northern district of Taipei, built the first carbon-ion irradiation facility in Taiwan.

METHODS

Taipei Veterans General Hospital completed a phase 1 trial to evaluate the safety of carbon-ion radiotherapy. Six patients (4 males and 2 females with prostate adenocarcinoma, sacral chordoma, hepatocellular carcinoma, lung adenocarcinoma, or parotid high-grade carcinoma) were enrolled in this study. The mean age of the patients was 62.7 years. The mean dose was 57.3 Gy(RBE) (fraction range, 4-16 Gy[RBE]).

RESULTS

During this phase 1 trial, all patients were monitored for 3 months to evaluate acute toxicity and short-term outcomes after treatment with carbon irradiation. Only 2 patients experienced grade 2 toxicity, which resolved without medication 1 month after completing treatment. The tumor response demonstrated 1 complete response, 1 partial response, and 4 cases of stable disease.

CONCLUSION

Carbon-ion radiotherapy was determined to be an effective and safe treatment.

Carbon-Ion Radiation Therapy for Adenocarcinoma of the Uterine Cervix: Clinical Outcomes of a Multicenter Prospective Registry-Based Study in Japan (2016-2020)

PURPOSE

Cases of adenocarcinoma of the uterine cervix (AUC) have poorer prognoses than those of squamous cell carcinoma. Carbon-ion radiation therapy (CIRT) outcomes for AUC have been reported in retrospective or single-institutional prospective studies but not prospective multicenter studies. We present the results of CIRT for AUC in a prospective multicenter study using a nationwide hospital-based registry in Japan.

METHODS AND MATERIALS

Patients with locally advanced untreated AUC who received CIRT at 4 Japanese centers between June 2016 and April 2020 were included in this study. In the absence of organ dysfunction, up to 5 weekly 40 mg/m2 cisplatin courses were administered. The primary endpoints were 2-year overall survival and local control rates. The secondary endpoints were 2-year disease-free survival rate and late adverse events (AEs).

RESULTS

Forty-two patients were enrolled with a median age of 54 years (range, 34-76 years). Patients were diagnosed with stage IIB (n = 26), IIIB (n = 12), or IVA (n = 4) disease. The median follow-up period was 24 months. The 2-year overall survival, local control, and disease-free survival rates were 97.5% (95% CI, 92.7%-100.0%), 80.9% (95% CI, 66.9%-94.8%), and 64.3% (48.1%-80.4%), respectively. Two patients developed grade 3 rectum/sigmoid AE. One patient required urinary diversion surgery during a salvage operation for local tumor recurrence (grade 3 genitourinary AE). No other grade 3 or worse toxicities were reported.

CONCLUSION

CIRT is an effective treatment for locally advanced AUC. Further research is required to validate the safety and efficacy of CIRT for AUC.

Radioresistant, Rare, Recurrent, and Radioinduced: 4Rs of Hadrontherapy for Patients Selections

Purpose

To describe the role of hadrontherapy (HT) in treating radioresistant, rare, recurrent, and radio-induced tumors, which can be defined, in assonance with the 4Rs of radiobiology, the "4Rs" of HT indications.

Materials and Methods

This is a narrative review written by a multidisciplinary team consisting of radiation oncologists, radiobiologists, and physicists on the current literature on HT, particularly carbon ion radiation therapy. To refine HT indications within the context of the "4Rs" framework, we evaluated tumor histologies across different clinical indication settings and emphasized the radiobiological mechanisms contributing to the effectiveness of HT.

Results

For rare, radioresistant, recurrent, and radio-induced tumors, HT has proven to be effective and safe, achieving high rates of local response with mild toxicity. The current review shows that the biological parameters can assist clinicians in identifying appropriate cases for HT treatment.

Conclusion

Biological characteristics of the tumor support the administration of HT in radioresistant, rare, recurrent, and radio-induced tumors and should be considered during multidisciplinary discussions.

Irradiation-responsive PRDM10-DT modulates the angiogenic response in human NSCLC cells in an SP1-dependent manner via the miR-663a/TGF-β1 axis

BACKGROUND

Photon radiation has been shown to stimulate the secretion of radioresistant factors from tumor cells, ultimately promoting tumor angiogenesis and metastasis. On the other hand, heavy-ion radiotherapy has been demonstrated to control tumor angiogenesis and metastasis levels. The molecular mechanisms responsible for the different angiogenic responses to photon and heavy-ion irradiation are not fully understood. This study aims to explore the irradiation-responsive genes related to tumor angiogenesis and reveal the regulatory effect.

METHODS

In order to clarify the potential regulatory mechanisms of tumor angiogenesis after X-ray or carbon ion (C-ion) irradiation, we performed RNA-sequencing (RNA-seq), as well as bioinformatics, public database analysis, Western blotting, immunohistochemistry, and immunofluorescence.

RESULTS

In this study, we identified the long intergenic noncoding RNA PRDM10 divergent transcript (PRDM10-DT), which was responsive to X-rays but not carbon ions. Mechanistically, PRDM10-DT triggers tumor angiogenesis by upregulating the TGF-β1/VEGF signaling pathway through its competitive binding to miR-663a. Additionally, the transcription factor SP1 facilitated the transcription of PRDM10-DT by binding to its promoter region. It's notable that the DNA-binding activity of SP1 was enhanced by reactive oxygen species (ROS). The knockdown of either PRDM10-DT or SP1 effectively inhibited NSCLC angiogenesis and metastasis.

CONCLUSION

These results illustrate the proangiogenic function of the PRDM10-DT/miR-663a/TGF-β1 axis and reveal the regulatory role of ROS and SP1 in the upstream response to radiation, with differential ROS production mediating the differential angiogenesis levels after X-ray and C-ion irradiation. Our findings suggest the potential of PRDM10-DT as a nucleic acid biomarker after radiotherapy and that targeting this gene could be a therapeutic strategy to counteract angiogenesis in NSCLC radiotherapy.

Nuclear interaction correction based on dual-energy computed tomography in carbon-ion radiotherapy

Objective.Accurate dose predictions are crucial to maximizing the benefits of carbon-ion therapy (CIT). Carbon beams incident on the human body cause nuclear interactions with tissues, resulting in changes in the constituent nuclides and leading to dose errors that are conventionally corrected using conventional single-energy computed tomography (SECT). Dual-energy computed tomography (DECT) has frequently been used for stopping power estimation in particle therapy and is well suited for correcting nuclear reactions because of its detailed body-tissue elemental information. This study proposes a correction method for the absolute dose in CIT that considers changes in nuclide composition resulting from nuclear reactions with body tissues, as a novel application of DECT.Approach.The change in dose associated with nuclear reactions is determined by correcting each integrated depth dose component of the carbon beam using a nuclear interaction correction factor. This factor is determined based on the stopping power, mass density, and nuclear interaction cross-section in body tissue. The stopping power and mass density were calculated using established methods, whereas the nuclear interaction cross-section was newly defined through a conversion equation derived from the effective atomic number.Main results.Nuclear interaction correction factors and corrected doses were determined for 85 body tissues with known compositions, comparing them with existing SECT-based methods. The root-mean-square errors of the SECT- and DECT-based nuclear interaction correction factors relative to theoretical values were 0.66% and 0.39%, respectively.Significance.This indicates a notable enhancement in the estimation accuracy with DECT. The dose calculations in uniform body tissues derived from SECT showed slight over-correction in adipose and bone tissues, whereas those based on DECT were almost consistent with theoretical values. Our proposed method demonstrates the potential of DECT for enhancing dose calculation accuracy in CIT, complementing its established role in stopping power estimation.

Recent developments in the field of radiotherapy for the management of lung cancer

Lung cancer has a poor prognosis, and further improvements in outcomes are needed. Radiotherapy plays an important role in the treatment of unresectable lung cancer, and there have been recent developments in the field of radiotherapy for the management of lung cancer. However, to date, there have been few reviews on the improvement in treatment outcomes associated with high precision radiotherapy for lung cancer. Thus, this review aimed to summarize the recent developments in radiotherapy techniques and indicate the future directions in the use of radiotherapy for lung cancer. Stereotactic body radiotherapy (SBRT) for unresectable stage I lung cancer has been reported to improve local control rates without severe adverse events, such as radiation pneumonitis. For locally advanced lung cancer, a combination of chemoradiotherapy and adjuvant immune checkpoint inhibitors dramatically improves treatment outcomes, and intensity-modulated radiotherapy (IMRT) enables safer radiation therapy with less frequent pneumonitis. Particle beam therapy, such as carbon-ion radiotherapy and proton beam therapy, has been administered as advanced medical care for patients with lung cancer. Since 2024, it has been covered under insurance for early stage lung cancer with tumors ≤ 5 cm in size in Japan. In addition to chemotherapy, local ablative radiotherapy improves treatment outcomes in patients with oligometastatic stage IV lung cancer. A particular problem with radiotherapy for lung cancer is that the target location changes with respiratory motion, and various physical methods have been used to control respiratory motion. Recently, coronavirus disease has had a major impact on lung cancer treatment, and cancer treatment during situations, such as the coronavirus pandemic, must be performed carefully. To improve treatment outcomes for lung cancer, it is necessary to fully utilize evolving radiotherapy modalities, and the role of radiotherapy in lung cancer treatment is expected to increase.

Optimal radiation dose to induce an abscopal effect by combining carbon-ion radiotherapy and anti-CTLA4 antibody

BACKGROUND AND PURPOSE

Although carbon-ion radiotherapy (CIRT) has led to good outcomes, controlling metastasis is still crucial for improving overall survival. This study aimed to evaluate the effectiveness of by two combinations, one of CIRT and anti-CTLA4 antibody, the other of CIRT and anti-PD-1 antibody, applied at different radiation doses for distal tumour and metastasis suppression.

MATERIALS AND METHODS

Murine cancer cells (colon carcinoma Colon-26 cells for experiments and osteosarcoma LM8 cells for verification) were grafted into both sides of the hind legs of syngeneic mice. Right-side tumours were irradiated with 3 Gy or 10 Gy CIRT while the left-side tumours were not irradiated, followed by the administration of the anti-CTLA4 antibody or anti-PD-1 antibody. The diameter of the tumours in both legs was measured 3 times per week after irradiation. The number of pulmonary metastases was evaluated within 3 weeks after irradiation.

RESULTS

Compared with the control group, the high-dose group showed promising anti-cancer benefits in terms of both irradiated tumours and lung metastasis, but neither 10 Gy CIRT combined with the anti-CTLA4 antibody nor 10 Gy CIRT combined with the anti-PD-1 antibody suppressed the growth of distant unirradiated tumours. In the low-dose group, the effect on primary tumour control was slightly weaker than that in the high-dose treatment group, but significant suppressive effects on both distant unirradiated tumours and metastases were observed following 3 Gy CIRT combined with anti-CTLA4 antibody treatment. Specifically, the volume of distant unirradiated tumours decreased by 40 % compared with that of the control group, and no lung metastasis was observed.

CONCLUSION

Our findings suggest that there is an optimal dose range for the abscopal effect generated with the CIRT combined with anti-CTLA4 antibody, and it highlights a new opportunity for increased induction efficiency of the abscopal effect of combination therapy.

Significant Effect of Carbon-Ion Radiation Therapy Combined With Androgen Deprivation on Biochemical Recurrence Rates in High-Risk Prostate Cancer Patients: A Two-Center Controlled Trial Compare With X-Ray External Beam Radiation Therapy

OBJECTIVE

To compare the effects of carbon-ion radiation therapy (CIRT) and external beam radiotherapy (EBRT) on the prognosis of patients with prostate cancer.

METHODS

The effects of initial prostate-specific antigen (iPSA), clinical Tumor (cT) stage, radiotherapy method, and other clinical factors on the prognosis of 577 patients with radiotherapy were analyzed.

RESULTS

Cox regression analysis showed that CIRT (RR: 0.49, p = 0.0215), cT stage ≥ 3 (RR: 2.72, p = 0.0003), and iPSA ≥ 16 ng/mL (RR: 1.74, p = 0.0347) were independent predictors of biochemical recurrence (BCR). After propensity score matching (PSM), CIRT (RR: 0.42, p = 0.0147), cT stage ≥ 3 (RR: 2.55, p = 0.0092), and iPSA ≥ 16 ng/mL (RR: 2.12, p = 0.0366) were still the predictors of univariate analysis. In multivariate analysis, CIRT (RR: 0.42, p = 0.015) and cT stage≥ 3 (RR:2.21, p = 0.0332) were independent predictors of BCR. Among them, we used iPSA and cT stages to establish a new radiotherapy selection model based on BCR risk. Patients who met more than one factor (score ≥ 1) and underwent CIRT had significantly better BCR progression-free survival (PFS) than those who received EBRT (p ≤ 0.01). This was also confirmed by Kaplan-Meier analysis after PSM.

CONCLUSION

CIRT patients exhibited lower 5-year BCR rates compared to the EBRT group. Patients with a risk score of our model ≥ 1 undergoing CIRT were more likely to experience BCR benefits compared to those receiving EBRT.

Tumor-Targeted Catalytic Immunotherapy

Cancer immunotherapy holds significant promise for improving cancer treatment efficacy; however, the low response rate remains a considerable challenge. To overcome this limitation, advanced catalytic materials offer potential in augmenting catalytic immunotherapy by modulating the immunosuppressive tumor microenvironment (TME) through precise biochemical reactions. Achieving optimal targeting precision and therapeutic efficacy necessitates a thorough understanding of the properties and underlying mechanisms of tumor-targeted catalytic materials. This review provides a comprehensive and systematic overview of recent advancements in tumor-targeted catalytic materials and their critical role in enhancing catalytic immunotherapy. It highlights the types of catalytic reactions, the construction strategies of catalytic materials, and their fundamental mechanisms for tumor targeting, including passive, bioactive, stimuli-responsive, and biomimetic targeting approaches. Furthermore, this review outlines various tumor-specific targeting strategies, encompassing tumor tissue, tumor cell, exogenous stimuli-responsive, TME-responsive, and cellular TME targeting strategies. Finally, the discussion addresses the challenges and future perspectives for transitioning catalytic materials into clinical applications, offering insights that pave the way for next-generation cancer therapies and provide substantial benefits to patients in clinical settings.

FLASH radiotherapy: mechanisms, nanotherapeutic strategy and future development

Ultra-high dose-rate (FLASH) radiotherapy serves as an ideal procedure to treat tumors efficiently without harming normal tissues and has demonstrated satisfactory antitumor effects in multiple animal tumor models. However, the biological mechanisms of FLASH radiotherapy have not yet been fully elucidated, and the small number of devices delivering FLASH dose rate has limited its wide application. This review summarizes the possible biological mechanisms and antitumor effects of FLASH radiotherapy, its application in nanotherapeutic strategy, as well as its challenges and future development. Furthermore, some valuable guidance for promoting the progress of FLASH radiotherapy in nanotherapeutic strategies are provided.

Distinct patterns of osteoradionecrosis after photon-based radiotherapy and carbon ion radiotherapy for unresectable adenoid cystic carcinoma of the head and neck: case series from two institutions

BACKGROUND AND PURPOSE

To present the clinical outcomes of two series of patients treated with carbon-ion radiotherapy (CIRT) and definitive photon radiotherapy (RT) for adenoid cystic carcinoma of the head and neck (HN-ACC).

MATERIAL AND METHODS

The first cohort of six patients was referred from Oslo University Hospital (OUS) to Centro Nazionale di Adroterapia Oncologica (CNAO, Pavia, Italy) for CIRT in 2014-2017. The second cohort included 18 patients treated with definitive photon RT at OUS in 2005-2017. The primary endpoint was an evaluation of osteoradionecrosis (ORN) in the two cohorts. The secondary endpoints were treatment efficacy by local control (LC), progression-free survival (PFS), and overall survival (OS).

RESULTS

The tumor stage was T4 for all the patients in the CIRT group and 15 (84%) in the photon group. There were three (50%) patients with grade 3 ORN in the CIRT group compared to one (6%) with grade 3 ORN in the photon group (p = 0.05). The 5-year LC (95% CI), PFS, and OS rates in the CIRT group and the photon group were 33% (11-100) and 39% (19-76), 17% (9-100) and 23% (2-59), and 80% (52-100) and 50% (31-82), respectively.

INTERPRETATION

Half of the patients in the CIRT cohort experienced ORN requiring surgical management during the follow-up. Patients with ACC referred for CIRT often have a worse prognosis and more advanced disease than patients treated with photons. When returning from the referring center, these patients need close follow-up often in collaboration with treating centers to manage toxicity that impacts quality of life.

Advanced Radiotherapy Technologies in Spine Tumors: What the Surgeon Needs to Know

STUDY DESIGN

Narrative review of existing literature.

OBJECTIVES

Significant technological advancements in radiotherapy planning and delivery have enabled new radiotherapy techniques for the management of spine tumors. The objective of this study was to provide a comprehensive summary of these treatment techniques for practicing spine surgeons.

METHODS

A narrative review of the existing literature on stereotactic body radiation therapy (SBRT) and particle beam therapy (PBT) for the treatment of spine tumors was performed. The characteristics, implementation and evidence supporting these strategies in the management of primary spinal neoplasms were summarized.

RESULTS

The clinical effectiveness of SBRT for the control and symptom palliation of metastatic spinal tumors are well demonstrated in multiple clinical trials. Risks such as fracture, radiculopathy and plexopathy exist after spine SBRT, necessitating an individualized approach in a well experienced multidisciplinary setting. SBRT should be considered a key component of a well-rounded treatment plan for metastatic spine tumors in combination with surgery, vertebral augmentation, and drug therapy, where indicated, to achieve optimal patient outcomes. Additionally, PBT and SBRT are also leading to promising results for primary spine tumors, though comparative effectiveness studies and prospective clinical trials are required to establish these modalities more formally as alternatives to conventionally fractionated photon radiotherapy.

CONCLUSIONS

SBRT and PBT are emerging as effective and well tolerated treatment options for primary and metastatic spine tumors. Additional investigation is needed to personalize these treatment options and further strengthen these approaches as key components in a multidisciplinary approach to the management of spinal neoplasms.

An empirical model of carbon-ion relative biological effectiveness based on the linear correlation between radiosensitivity to photons and carbon ions

Objective.To develop an empirical model to predict carbon ion (C-ion) relative biological effectiveness (RBE).Approach.We used published cell survival data comprising 360 cell line/energy combinations to characterize the linear energy transfer (LET) dependence of cell radiosensitivity parameters describing the dose required to achieve a given survival level, e.g. 5% (D5%), which are linearly correlated between photon and C-ion radiations. Based on the LET response of the metrics D5%and D37%, we constructed a model containing four free parameters that predicts cells' linear quadratic model (LQM) survival curve parameters for C-ions,αCandβC, from the reference LQM parameters for photons,αXandβX, for a given C-ion LET value. We fit our model's free parameters to the training dataset and assessed its accuracy via leave-one out cross-validation. We further compared our model to the local effect model (LEM) and the microdosimetric kinetic model (MKM) by comparing its predictions against published predictions made with those models for clinically relevant LET values in the range of 23-107 keVμm-1.Main Results.Our model predicted C-ion RBE within ±7%-15% depending on cell line and dose which was comparable to LEM and MKM for the same conditions.Significance.Our model offers comparable accuracy to the LEM or MKM but requires fewer input parameters and is less computationally expensive and whose implementation is so simple we provide it coded into a spreadsheet. Thus, our model can serve as a pragmatic alternative to these mechanistic models in cases where cell-specific input parameters cannot be obtained, the models cannot be implemented, or for which their computational efficiency is paramount.

The first Korean carbon-ion radiation therapy facility: current status of the Heavy-ion Therapy Center at the Yonsei Cancer Center

PURPOSE

This report offers a detailed examination of the inception and current state of the Heavy-ion Therapy Center (HITC) at the Yonsei Cancer Center (YCC), setting it apart as the world's first center equipped with a fixed beam and two superconducting gantries for carbon-ion radiation therapy (CIRT).

MATERIALS AND METHODS

Preparations for CIRT at YCC began in 2013; accordingly, this center has completed a decade of meticulous planning and culminating since the operational commencement of the HITC in April 2023.

RESULTS

This report elaborates on the clinical preparation for adopting CIRT in Korea. It includes an extensive description of HITC's facility layout at YCC, which comprises the accelerator and treatment rooms. Furthermore, this report delineates the clinical workflow, criteria for CIRT application, and the rigorous quality assurance processes implemented at YCC. It highlights YCC's sophisticated radiation therapy infrastructure, collaborative initiatives, and the efficacious treatment of >200 prostate cancer cases utilizing CIRT.

CONCLUSION

This manuscript concludes by discussing the prospective influence of CIRT on the medical domain within Korea, spotlighting YCC's pioneering contribution and forecasting the widespread integration of this groundbreaking technology.

Vaginal Mucosal Melanoma Cell Activation in Response to Photon or Carbon Ion Irradiation

Purpose

Primary gynecological melanomas are uncommon with lower survival rates compared to cutaneous melanomas. Although melanocytes have been identified in a variety of mucosal membranes, little is known about their interactions or roles inside the mucosa layer. Melanin is a common pigment in nature and is endowed with several peculiar chemical, paramagnetic, and semiconductive characteristics. One of its latest explored functions is its interaction with ionizing radiation as a protective mechanism as well as its implication in the metastatic cascade of tumor cells.

Materials and Methods

In this work, we analyzed in vitro the effects of different doses of photon and carbon ion irradiation on dendrite formation, pigmentation, migration, and invasion abilities of human mucosal melanoma cells of the vagina. We evaluated the morphology and melanin production of HMV-II cells exposed to photon and carbon ion beams with single doses between 0.5 and 10 Gy.

Results

Our results showed that irradiation induces dendrite formation or elongation and pigmentation in HMV-II cells in a dose-type-dependent and radiation-type-dependent way but also a decrease in cell motility.

Conclusion

The present study describes for the first time an induction of dendritic formation, melanin production, and alterations in migration and invasion abilities by low-linear energy transfer and high-linear energy transfer radiation in human mucosal melanoma cells, suggesting a radioprotective response to further possible exposures increasing the radioresistance of these cells.

Impact of COVID-19 Pandemic on Carbon-Ion Radiation Therapy in Japan: A Japanese National Registry Study

Purpose

This study aimed to investigate the impact of the COVID-19 pandemic on carbon-ion radiation therapy (CIRT) in Japan by evaluating patient numbers and treatment trends from 2019 to 2022.

Patients and Methods

Data from 5 CIRT facilities were analyzed, encompassing a total of 13 224 patients treated over the 4-year period. Patient demographics, cancer types, treatment protocols, and adherence to national health insurance coverage were examined. The study period was divided into unaffected (2019), significantly affected (2020-2021), and poststabilization (2022) phases, corresponding to progression of the pandemic. For monthly analysis, the period during which a state of emergency was declared by the Japanese government was defined as the pandemic period.

Results

Prostate cancer comprised the majority of CIRT cases (62.4%), followed by hepatocellular carcinoma, bone and soft tissue tumors, locally advanced pancreatic cancer, and nonsquamous cell carcinoma of the head and neck. Despite the pandemic, the annual reduction in CIRT patients remained <5%, suggesting treatment continuity. Analysis of monthly treatment figures revealed a significant reduction in the number of patients with nonprostate cancers treated during the state of emergency, while a reduction in the number of prostate cancer treatments was observed approximately 6 months later. Although the number of COVID-19 patients continued to increase after 2022, the number of patients receiving CIRT increased after the state of emergency was declared.

Conclusion

Although there was a reduction in monthly CIRT patient numbers during the COVID-19 pandemic, yearly analysis revealed that this amounted to <5%.

PU-H71 (NSC 750424): a molecular masterpiece that targets HSP90 in cancer and beyond

Heat shock protein 90 (HSP90) is a pivotal molecular chaperone with multifaceted roles in cellular health and disease. Herein, we explore how HSP90 orchestrates cellular stress responses, particularly through its partnership with heat shock factor 1 (HSF-1). PU-H71, a selective inhibitor of HSP90, demonstrates significant potential in cancer therapy by targeting a wide array of oncogenic pathways. By inducing the degradation of multiple client proteins, PU-H71 disrupts critical signaling pathways such as MAPK, PI3K/Akt, JAK/STAT, EGFR, and mTOR, which are essential for cancer cell survival, proliferation, and metastasis. We examined its impact on combating triple-negative breast cancer and enhancing the effectiveness of carbon-ion beam therapy, offering new avenues for cancer treatment. Furthermore, the dual inhibition of HSP90A and HSP90B1 by PU-H71 proves highly effective in the context of myeloma, providing fresh hope for patients with this challenging malignancy. We delve into its potential to induce apoptosis in B-cell lymphomas that rely on Bcl6 for survival, highlighting its relevance in the realm of hematologic cancers. Shifting our focus to hepatocellular carcinoma, we explore innovative approaches to chemotherapy. Moreover, the current review elucidates the potential capacity of PU-H71 to suppress glial cell activation paving the way for developing novel therapeutic strategies for neuroinflammatory disorders. Additionally, the present report also suggests the promising role of PU-H71 in JAK2-dependent myeloproliferative neoplasms. Eventually, our report sheds more light on the multiple functions of HSP90 protein as well as the potential therapeutic benefit of its selective inhibitor PU-H71 in the context of an array of diseases, laying the foundations for the development of novel therapeutic approaches that could achieve better treatment outcomes.

Rotationally Intensified Proton Lattice: A Novel Lattice Technique Using Spot-Scanning Proton Arc Therapy

Purpose

The aim of this study was to explore the feasibility and dosimetric advantage of using spot-scanning proton arc (SPArc) for lattice radiation therapy in comparison with volumetric-modulated arc therapy (VMAT) and intensity modulated proton therapy (IMPT) lattice techniques.

Methods

Lattice plans were retrospectively generated for 14 large tumors across the abdomen, pelvis, lung, and head-and-neck sites using VMAT, IMPT, and SPArc techniques. Lattice geometries comprised vertices 1.5 cm in diameter that were arrayed in a body-centered cubic lattice with a 6-cm lattice constant. The prescription dose was 20 Gy (relative biological effectiveness [RBE]) in 5 fractions to the periphery of the tumor, with a simultaneous integrated boost of 66.7 Gy (RBE) as a minimum dose to the vertices. Organ-at-risk constraints per American Association of Physicists in Medicine Task Group 101were prioritized. Dose-volume histograms were extracted and used to identify maximum, minimum, and mean doses; equivalent uniform dose; D95%, D50%, D10%, D5%; V19Gy; peak-to-valley dose ratio (PVDR); and gradient index (GI). The treatment delivery time of IMPT and SPArc were simulated based on the published proton delivery sequence model.

Results

Median tumor volume was 577 cc with a median of 4.5 high-dose vertices per plan. Low-dose coverage was maintained in all plans (median V19Gy: SPArc 96%, IMPT 96%, VMAT 92%). SPArc generated significantly greater dose gradients as measured by PVDR (SPArc 4.0, IMPT 3.6, VMAT 3.2; SPArc-IMPT P = .0001, SPArc-VMAT P < .001) and high-dose GI (SPArc 5.9, IMPT 11.7, VMAT 17.1; SPArc-IMPT P = .001, SPArc-VMAT P < .01). Organ-at-risk constraints were met in all plans. Simulated delivery time was significantly improved with SPArc compared with IMPT (510 seconds vs 637 seconds, P < .001).

Conclusions

SPArc therapy was able to achieve high-quality lattice plans for various sites with superior gradient metrics (PVDR and GI) when compared with VMAT and IMPT. Clinical implementation is warranted.

Intensity Modulated Carbon Ion Radiation Therapy Using Pencil Beam Scanning Technology for Patients With Unresectable Sacrococcygeal Chordoma

Purpose

To investigate the safety and efficacy of intensity modulated carbon ion radiation therapy (IM-CIRT) using pencil beam scanning technology for patients with unresectable sacrococcygeal chordoma (SC).

Methods and Materials

A total of 35 patients with unresectable SC were retrospectively analyzed, including 54.3% (19/35) recurrent cases. In 68.6% (24/35) cases, tumor was located in S2 or above, and all cases were treated with hypofractionated IM-CIRT. The median dose was 70.4 Gy (range, 69-80 Gy) (relative biologic effectiveness) in 16 fractions (range, 16-23 fractions), typically delivered over 5 fractions per week.

Results

The 3-year overall survival, cause-specific survival, progression-free survival, locoregional progression-free survival, and distant metastasis-free survival rates with a median follow-up time of 42 months (range, 12-91 months) for the entire cohort were 93.2%, 96.3%, 61.8%, 80%, and 77.3%, respectively. Multivariate analysis revealed that gross tumor volume (hazard ratio, 3.807; 95% CI, 1.044-13.887; P = .043) was the only significant prognostic factor for progression-free survival and the dose for the gross tumor volume ≥70.4 Gy (relative biologic effectiveness) was relevant with significantly better locoregional progression-free survival (hazard ratio, 0.190; 95% CI, 0.038-0.940; P = .042). No significant prognostic factor for overall survival, cause-specific survival, and distant metastasis-free survival and no severe (ie, grade ≥3) acute toxicity were identified. Severe late toxicities occurred in 3 patients (8.57%): pain (1 patient), motor neuropathy (1 patient), and skin ulcer (1 patient). Furthermore, no severe toxicity related to urinary function or defecation was observed following IM-CIRT. Pain grades improved or remained unchanged in 85.7% of patients.

Conclusions

IM-CIRT produced acceptable 3-year outcomes without substantial late adverse effects, especially urinary and anorectal complications for SC, and did not appear to increase pain. IM-CIRT at high doses using hypofractionated radiation therapy may improve outcomes for local control and seems to be feasible even for postoperative recurrent SC.

Irradiation with Carbon Ions Effectively Counteracts Hypoxia-related Radioresistance in a Rat Prostate Carcinoma

PURPOSE

Hypoxia in tumors is associated with increased malignancy and resistance to conventional photon radiation therapy. This study investigated the potential of particle therapy to counteract radioresistance in syngeneic rat prostate carcinoma.

METHODS AND MATERIALS

Subcutaneously transplanted R3327-HI tumors were irradiated with photons or carbon ions under acute hypoxic conditions, induced by clamping the tumor-supplying artery 10 min before and during irradiation. Dose-response curves were determined for the endpoint "local tumor control within 300 days" and compared with previously published data acquired under oxic conditions. Doses at 50% tumor control probability (TCD50) were used to quantify hypoxia-induced radioresistance relative to that under oxic conditions and also to quantify the increased effectiveness of carbon ions under oxic and hypoxic conditions relative to photons.

RESULTS

Compared with those under oxic conditions, TCD50 values under hypoxic conditions increased by a factor of 1.53 ± 0.08 for photons and by a factor of 1.28 ± 0.06 for carbon ions (oxygen enhancement ratio). Compared with those for photons, TCD50 values for carbon ions decreased by a factor of 2.08 ± 0.13 under oxic conditions and by a factor of 2.49 ± 0.08 under hypoxic conditions (relative biological effectiveness). While the slope of the photon dose-response curves increased when changing from oxic to hypoxic conditions, the slopes were steeper and remained unchanged for carbon ions.

CONCLUSIONS

The reduced oxygen enhancement ratio of carbon ions indicated that the required dose increase in hypoxic tumors was 17% lower for carbon ions than for photons. Additionally, carbon ions reduced the effect of intertumor heterogeneity on the radiation response. Therefore, carbon ions may confer a significant advantage for the treatment of hypoxic tumors that are highly resistant to conventional photon radiation therapy.

A Practical Primer on Particle Therapy

PURPOSE

Particle therapy is a promising treatment technique that is becoming more commonly used. Although proton beam therapy remains the most commonly used particle therapy, multiple other heavier ions have been used in the preclinical and clinical settings, each with its own unique properties. This practical review aims to summarize the differences between the studied particles, discussing their radiobiological and physical properties with additional review of the available clinical data.

METHODS AND MATERIALS

A search was carried out on the PubMed databases with search terms related to each particle. Relevant radiobiology, physics, and clinical studies were included. The articles were summarized to provide a practical resource for practicing clinicians.

RESULTS

A total of 113 articles and texts were included in our narrative review. Currently, proton beam therapy has the most data and is the most widely used, followed by carbon, helium, and neutrons. Although oxygen, neon, silicon, and argon have been used clinically, their future use will likely remain limited as monotherapy.

CONCLUSIONS

This review summarizes the properties of each of the clinically relevant particles. Protons, helium, and carbon will likely remain the most commonly used, although multi-ion therapy is an emerging technique.

Secondary Osteosarcoma After Carbon-Ion Radiotherapy for Desmoid-Type Fibromatosis: A Case Report

BACKGROUND

Radiotherapy is considered an alternative treatment for unresectable or pharmacologically resistant desmoid-type fibromatosis. While it results in relatively good local control, the risk of secondary malignancy remains a concern.

CASE

We present a case of secondary osteosarcoma after carbon-ion radiation therapy (CIRT). A 31-year-old male patient presented with left thigh pain. The tumor was located between the left gluteus maximus and gluteus medius and extended to the vastus lateralis and biceps femoris. It was diagnosed as desmoid-type fibromatosis after needle biopsy. The patient was treated with several medications, including a cyclooxygenase 2 inhibitor and tamoxifen; however, his left thigh pain did not improve. He was treated with CIRT 1 year after diagnosis (67.2 Gy [relative biological effectiveness] 16fr/4wks). He developed osteosarcoma of the left femur 8 years later. He underwent chemotherapy and tumor excision with disarticulation of the left hip. Pulmonary metastasis was detected 6 and 17 months after the definitive surgery and excised using metastasectomy. However, he died due to the recurrence of multiple pulmonary metastases 29 months after the definitive surgery.

CONCLUSIONS

In this case, we believe that the low radiation dose to the femur may have caused secondary malignancy.

Combined effects of carbon ion radiation and PARP inhibitor on non-small cell lung carcinoma cells: Insights into DNA repair pathways and cell death mechanisms

The utilization of high linear energy transfer (LET) carbon ion (12C-ion) in radiotherapy has witnessed a notable rise in managing highly metastatic, recurrent, and chemo/radio-resistant human cancers. Non-small cell lung cancer (NSCLC) presents a formidable challenge due to its chemo-resistance and aggressive nature, resulting in poor prognosis and survival rates. In a previous study, we demonstrated that the combination of 12C-ion with the poly (ADP-ribose) polymerase (PARP) inhibitor (PARPi) olaparib significantly mitigated metastasis in A549 cells. Here, we delve into the underlying rationale behind the combined action of olaparib with 12C-ion, focusing on DNA repair pathways and cell death mechanisms in asynchronous NSCLC A549 cells following single and combined treatments. Evaluation included analysis of colony-forming ability, DNA damage assessed by γH2AX foci, expression profiling of key proteins involved in Homologous Recombination (HR) and Non-Homologous End Joining (NHEJ) repair pathways, caspase-3 activation, apoptotic body formation, and autophagic cell death. Our findings reveal that both PARPi olaparib and rucaparib sensitize A549 cells to 12C-ion exposure, with olaparib exhibiting superior sensitization. Moreover, 12C-ion exposure alone significantly downregulates both HR and NHEJ repair pathways by reducing the expression of MRE11--RAD51 and Ku70-Ku80 protein complexes at 24 h post-treatment. Notably, the combination of olaparib pre-treatment with 12C-ion markedly inhibits both HR and NHEJ pathways, culminating in DNA damage-induced apoptotic and autophagic cell death. Thus we are the first to demonstrate that olaparib sensitizes NSCLC cells to carbon ion by interfering with HR and NHEJ pathway. These insights underscore the promising therapeutic potential of combining PARP inhibition with carbon ion exposure for effective NSCLC management.

Particle Beam Radiobiology Status and Challenges: A PTCOG Radiobiology Subcommittee Report

Particle therapy (PT) represents a significant advancement in cancer treatment, precisely targeting tumor cells while sparing surrounding healthy tissues thanks to the unique depth-dose profiles of the charged particles. Furthermore, their linear energy transfer and relative biological effectiveness enhance their capability to treat radioresistant tumors, including hypoxic ones. Over the years, extensive research has paved the way for PT's clinical application, and current efforts aim to refine its efficacy and precision, minimizing the toxicities. In this regard, radiobiology research is evolving toward integrating biotechnology to advance drug discovery and radiation therapy optimization. This shift from basic radiobiology to understanding the molecular mechanisms of PT aims to expand the therapeutic window through innovative dose delivery regimens and combined therapy approaches. This review, written by over 30 contributors from various countries, provides a comprehensive look at key research areas and new developments in PT radiobiology, emphasizing the innovations and techniques transforming the field, ranging from the radiobiology of new irradiation modalities to multimodal radiation therapy and modeling efforts. We highlight both advancements and knowledge gaps, with the aim of improving the understanding and application of PT in oncology.

Understanding Relative Biological Effectiveness and Clinical Outcome of Prostate Cancer Therapy Using Particle Irradiation: Analysis of Tumor Control Probability With the Modified Microdosimetric Kinetic Model

PURPOSE

Recent experimental studies and clinical trial results might indicate that-at least for some indications-continued use of the mechanistic model for relative biological effectiveness (RBE) applied at carbon ion therapy facilities in Europe for several decades (LEM-I) may be unwarranted. We present a novel clinical framework for prostate cancer treatment planning and tumor control probability (TCP) prediction based on the modified microdosimetric kinetic model (mMKM) for particle therapy.

METHODS AND MATERIALS

Treatment plans of 91 patients with prostate tumors (proton: 46, carbon ions: 45) applying 66 GyRBE [RBE = 1.1 for protons and LEM-I, (α/β)x = 2.0 Gy, for carbon ions] in 20 fractions were recalculated using mMKM [(α/β)x = 3.1 Gy]). Based solely on the response data of photon-irradiated patient groups stratified according to risk and usage of androgen deprivation therapy, we derived parameters for an mMKM-based Poisson-TCP model. Subsequently, new carbon and helium ion plans, adhering to prescribed biological dose criteria, were generated. These were systematically compared with the clinical experience of Japanese centers employing an analogous fractionation scheme and existing proton plans.

RESULTS

mMKM predictions suggested significant biological dose deviation between the proton and carbon ion arms. Patients irradiated with protons received (3.25 ± 0.08)  GyRBEmMKM/Fx, whereas patients treated with carbon ions received(2.51 ± 0.05)  GyRBEmMKM/Fx. TCP predictions were (86 ± 3)% for protons and (52 ± 4)% for carbon ions, matching the clinical outcome of 85% and 50%. Newly optimized carbon ion plans, guided by the mMKM/TCP model, effectively replicated clinical data from Japanese centers. Using mMKM, helium ions exhibited similar target coverage as proton and carbon ions and improved rectum and bladder sparing compared with proton.

CONCLUSIONS

Our mMKM-based model for prostate cancer treatment planning and TCP prediction was validated against clinical data for proton and carbon ion therapy, and its application was extended to helium ion therapy. Based on the data presented in this work, mMKM seems to be a good candidate for clinical biological calculations in carbon ion therapy for prostate cancer.

Dosimetric impact of stopping power for human bone porosity with dual-energy computed tomography in scanned carbon-ion therapy treatment planning

Few reports have documented how the accuracy of stopping power ratio (SPR) prediction for porous bone tissue affects the dose distribution of scanned carbon-ion beam therapy. The estimated SPR based on single-energy computed tomography (SECT) and dual-energy CT (DECT) were compared for the femur of a Rando phantom which simulates the porosity of human bone, NEOBONE which is the hydroxyapatite synthetic bone substitute, and soft tissue samples. Dose differences between SECT and DECT were evaluated for a scanned carbon-ion therapy treatment plan for the Rando phantom. The difference in the water equivalent length was measured to extract the SPR of the examined samples. The differences for SPR estimated from the DECT-SPR conversion were small with - 1.8% and - 3.3% for the Rando phantom femur and NEOBONE, respectively, whereas the differences for SECT-SPR were between 7.6 and 70.7%, illustrating a 1.5-mm shift of the range and a dose difference of 13.3% at maximum point in the evaluation of the dose distribution. This study demonstrated that the DECT-SPR conversion method better estimated the SPR of the porosity of bone tissues than SECT-SPR followed by the accurate range of the carbon-ion beams on carbon-ion dose calculations.

Correlation between dose-volume parameters and rectal bleeding after 12 fractions of carbon ion radiotherapy for prostate cancer

BACKGROUND

Carbon ion radiotherapy (CIRT) is currently used to treat prostate cancer. Rectal bleeding is a major cause of toxicity even with CIRT. However, to date, a correlation between the dose and volume parameters of the 12 fractions of CIRT for prostate cancer and rectal bleeding has not been shown. Similarly, the clinical risk factors for rectal bleeding were absent after 12 fractions of CIRT.

AIM

To identify the risk factors for rectal bleeding in 12 fractions of CIRT for prostate cancer.

METHODS

Among 259 patients who received 51.6 Gy [relative biological effectiveness (RBE)], in 12 fractions of CIRT, 15 had grade 1 (5.8%) and nine had grade 2 rectal bleeding (3.5%). The dose-volume parameters included the volume (cc) of the rectum irradiated with at least x Gy (RBE) (Vx) and the minimum dose in the most irradiated x cc normal rectal volume (Dx).

RESULTS

The mean values of D6cc, D2cc, V10 Gy (RBE), V20 Gy (RBE), V30 Gy (RBE), and V40 Gy (RBE) were significantly higher in the patients with rectal bleeding than in those without. The cutoff values were D6cc = 34.34 Gy (RBE), D2cc = 46.46 Gy (RBE), V10 Gy (RBE) = 9.85 cc, V20 Gy (RBE) = 7.00 cc, V30 Gy (RBE) = 6.91 cc, and V40 Gy (RBE) = 4.26 cc. The D2cc, V10 Gy (RBE), and V20 Gy (RBE) cutoff values were significant predictors of grade 2 rectal bleeding.

CONCLUSION

The above dose-volume parameters may serve as guidelines for preventing rectal bleeding after 12 fractions of CIRT for prostate cancer.

Preliminary result of combined treatment with scanning carbon-ion radiotherapy and image-guided brachytherapy for locally advanced cervical adenocarcinoma

Although there is growing evidence of the efficacy of carbon-ion radiotherapy (CIRT) for locally advanced cervical adenocarcinoma, reports on combined treatment with CIRT and image-guided brachytherapy (IGBT) are scarce. We retrospectively analyzed patients with International Federation of Gynecology and Obstetrics (2008) stage II-IVA locally advanced cervical adenocarcinoma who received combined scanning CIRT (sCIRT) and IGBT between April 2019 and March 2022. sCIRT consisted of whole-pelvic irradiation with 36 Gy (relative biological effectiveness [RBE]) in 12 fractions and subsequent local boost irradiation with 19.2 Gy (RBE) in 4 fractions. Three sessions of IGBT were administered after completion of sCIRT. Concurrent chemotherapy using weekly cisplatin (40 mg/m2/week) was also administered. Efficacy, toxicity and dose-volume parameters were analyzed. Fifteen patients were included in the analysis. The median follow-up period was 25 months. The 2-year overall survival, progression-free survival and local control rates were 92.3% (95% confidence interval [CI] = 77.8-100%), 52.5% (95% CI = 26.9-78.1%) and 84.8% (95% CI = 65.2-100%), respectively. Neither severe acute toxicity necessitating treatment cessation nor grade 3 or higher late toxicity were observed. The sigmoid D2cm3 of the patient who developed grade 2 late sigmoid hemorrhage was 65.6 Gy, which exceeded the standard deviation and target dose. The combination of sCIRT and IGBT for locally advanced cervical adenocarcinoma showed acceptable efficacy and safety. Further large-scale and long-term studies are warranted to confirm the efficacy and safety of this treatment.

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.

Chronic Encapsulated Intracerebral Hematoma after Carbon Ion Therapy for Chordoma Mimicking Malignant Glioma: A Case Report

Chronic encapsulated intracerebral hematoma is a rare type of intracerebral hemorrhage. Reportedly, it is associated with vascular malformations, including arteriovenous malformations, cavernous hemangiomas, microaneurysms, and venous malformations. Recently, an association between chronic encapsulated intracerebral hematoma and stereotactic radiosurgery for arteriovenous malformations has been reported. In general, as the hematoma enlarges, symptoms progress slowly. In this report, we present a case of a 50-year-old woman who had undergone clivus chordoma resection and carbon ion therapy for the clivus respectively 27 and 20 years before developing chronic encapsulated intracerebral hematoma with rapidly progressing disturbance of consciousness. She was referred to our hospital because of difficulty walking due to left hemiparesis. Head computed tomography and magnetic resonance imaging showed a cystic lesion in the right temporal lobe with perifocal edema. On the second day of hospitalization, the patient's consciousness worsened. We suspected a malignant glioma and performed an emergency craniotomy; however, the pathological diagnosis was chronic encapsulated intracerebral hematoma. After the rehabilitation therapy, the patient became ambulatory and was discharged. To the date of reporting, the patient remained recurrence-free. Chronic encapsulated intracerebral hematoma may be due to invasive craniotomy or carbon ion therapy. It usually progresses slowly; however, in some cases, such as this one, it may cause rapid deterioration of consciousness.

Radioresistance or/and radiosensitivity of head and neck squamous cell carcinoma: biological angle

OBJECTIVE

This narrative review aimed to compile and summarize clinically relevant literature in radiation therapy and to discuss the potential in radioresistant and radiosensitive head and neck squamous cell carcinoma (HNSCC).

METHODS AND MATERIALS

Google Scholar, PubMed, and the Cochrane Library were retrieved using combined key words such as "radiotherapy" and "head and neck cancer." Search strings additionally queried were "radioresistant," "radiosensitive," "head and neck region," "squamous cell carcinoma," in combination with Boolean operators 'AND' and 'OR.' Subsequently, the resulting publications were included for review of the full text.

RESULTS

Radiotherapeutic responses currently in clinical observation referred to HNSCC scoping were selected into this review. The compiled mechanisms were then detailed concerning on the clinical significance, biological characteristics, and molecular function.

CONCLUSIONS

Brachytherapy or/and external-beam radiotherapy are crucial for treating HNSCC especially the early stage patients, but in some patients with locally advanced tumors, their outcome with radiation therapy is poor due to obvious radioresistance. The curative effects mainly depend on the response to radiation therapy so an updated review is needed to optimize further applications in HNSCC radiotherapy.

Inter-fractional error and intra-fractional motion of prostate and dosimetry comparisons of patient position registrations with versus without fiducial markers during treatment with carbon-ion radiotherapy

A few reports have discussed the influence of inter-fractional position error and intra-fractional motion on dose distribution, particularly regarding a spread-out Bragg peak. We investigated inter-fractional and intra-fractional prostate position error by monitoring fiducial marker positions. In 2020, data from 15 patients with prostate cancer who received carbon-ion beam radiotherapy (CIRT) with gold markers were investigated. We checked marker positions before and during irradiation to calculate the inter-fractional positioning and intra-fractional movement and evaluated the CIRT dose distribution by adjusting the planning beam isocenter and clinical target volume (CTV) position. We compared the CTV dose coverages (CTV receiving 95% [V95%] or 98% [V98%] of the prescribed dose) between skeletal and fiducial matching irradiation on the treatment planning system. For inter-fractional error, the mean distance between the marker position in the planning images and that in a patient starting irradiation with skeletal matching was 1.49 ± 1.11 mm (95th percentile = 1.85 mm). The 95th percentile (maximum) values of the intra-fractional movement were 0.79 mm (2.31 mm), 1.17 mm (2.48 mm), 1.88 mm (4.01 mm), 1.23 mm (3.00 mm), and 2.09 mm (8.46 mm) along the lateral, inferior, superior, dorsal, and ventral axes, respectively. The mean V95% and V98% were 98.2% and 96.2% for the skeletal matching plan and 99.5% and 96.8% for the fiducial matching plan, respectively. Fiducial matching irradiation improved the CTV dose coverage compared with skeletal matching irradiation for CIRT for prostate cancer.

Current status and prospect of particle therapy for esophageal cancer

Esophageal cancer is among the top causes of cancer-related mortality worldwide, and the main treatment modality for locally advanced esophageal cancer is concurrent chemoradiotherapy. The current photon-based radiotherapy modalities and procedures have increased the incidence of treatment-related cardiac and pulmonary complications. Additionally, anatomical changes in the esophagus resulting from diaphragmatic movement, weight loss, and tumor progression present challenges for radiotherapy. These challenges have spurred interest in particle therapies, such as proton beam therapy (PBT) and heavy-ion therapy, for esophageal cancer. This paper comprehensively reviews the dosimetric advantages, clinical efficacy, and limitations of PBT and heavy-ion therapy for esophageal cancer and discusses their prospects. This highlights the unique dosimetric benefits of these therapies, particularly their ability to deliver high-dose radiation precisely to the tumor while sparing the surrounding normal organs and tissues. Although PBT and heavy-ion therapy demonstrate superior clinical efficacy compared to photon therapy, they are not without limitations. Multiple studies are needed to further validate and supplement the existing clinical and preclinical data to better exploit the benefits of PBT and thereby provide improved survival advantages to these patients.

Effectiveness and Safety of Carbon Ion Radiotherapy in Solid Tumors: A Systematic Review and Meta-Analysis

PURPOSE

This systematic review and meta-analysis aimed to investigate the effectiveness of carbon ion radiotherapy (CIRT) compared to that of conventional radiotherapy in patients with various types of solid tumors.

MATERIALS AND METHODS

We systematically searched eight electronic databases from inception until August 2022 in accordance with the Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines. The comparative effectiveness of the different treatment options was assessed by a random-effects meta-analysis.

RESULTS

This review included 34 comparative studies and three treatment groups. Overall, the meta-analysis indicated comparable local control rates between the CIRT and control groups [pooled risk ratio (RR)=1.02, 95% confidence interval (CI) 0.90-1.15]. The local control rate in the CIRT group was higher than that in the photon therapy group, but slightly lower than that in the proton radiation therpy (PRT) group. Additionally, the CIRT group had significantly higher overall survival (OS) (RR=1.19, 95% CI=1.01-1.42) and progression-free survival (PFS) (RR=1.50, 95% CI=1.01-2.21) rates compared to the control group. In the subgroup analysis, survival rates were similar between the CIRT and PRT groups.

CONCLUSION

CIRT was associated with improved toxicity, local tumor control, OS, and PFS compared to conventional treatments. Therefore, CIRT was found to be a safe and effective option for achieving local control in patients with solid tumors.

Monte carlo simulation study on the dose and dose-averaged linear energy transfer distributions in carbon ion radiotherapy

Dose-averaged linear energy transfer (LETd) is conventionally evaluated from the relative biological effectiveness (RBE)-LETd fitted function used in the treatment planning system. In this study, we calculated the physical doses and their linear energy transfer (LET) distributions for patterns of typical CIRT beams using Monte Carlo (MC) simulation. The LETd was then deduced from the MC simulation and compared with that obtained from the conventional method. The two types of LETd agreed well with each other, except around the distal end of the spread-out Bragg peak. Furthermore, an MC simulation was conducted with the material composition of water and realistic materials. The profiles of physical dose and LETd were in good agreement for both techniques. These results indicate that the previous studies to analyze the minimum LETd in CIRT cases are valid for practical situations, and the material composition conversion to water little affects the dose distribution in the irradiation field.

Carbon ion radiotherapy for mesonephric adenocarcinoma of the uterine cervix: a case report

BACKGROUND

Mesonephric adenocarcinoma is an extremely rare subtype of uterine cervical cancer that is associated with a poor prognosis and for which a standardized treatment protocol has not been established. Carbon ion radiotherapy (CIRT) is an emerging radiotherapy modality that has been shown to have a favorable anti-tumor effect, even for tumors resistant to conventional photon radiotherapy or chemotherapy. However, there is no report on CIRT outcomes for mesonephric adenocarcinoma of the uterine cervix.

CASE PRESENTATION

We treated a 47-year-old Japanese woman with mesonephric adenocarcinoma of the uterine cervix (T2bN0M0 and stage IIB according to the 7th edition of the Union for International Cancer Control and International Federation of Gynecology and Obstetrics, respectively) with CIRT combined with brachytherapy and concurrent chemotherapy. CIRT consisted of whole pelvic irradiation and boost irradiation to the gross tumor; 36.0 Gy (relative biological effectiveness [RBE]) in 12 fractions and 19.2 Gy (RBE) in 4 fractions, respectively, performed once a day, four times per week. Computed tomography-based image-guided adaptive brachytherapy was performed after completion of CIRT, for which the D90 (i.e., the dose prescribed to 90% of the target volume) for the high-risk clinical target volume was 20.4 Gy in a total of 3 sessions in 2 weeks. A weekly cisplatin (40 mg/m2) dose was administered concomitantly with the radiotherapy for a total of five courses. From 4 months post-CIRT, the patient developed metastasis of the lung, with a total of 10 lung metastases over 70 months; these lesions were treated on each occasion by photon stereotactic body radiotherapy and/or systemic therapy. At 8 years from initial treatment (i.e., 2 years after the last treatment), the patient is alive without any evidence of recurrence and maintains a high quality of life.

CONCLUSIONS

This is the first report of CIRT for treatment of mesonephric adenocarcinoma of the uterine cervix. The present case indicates the potential efficacy of CIRT in combination with brachytherapy for treatment of this disease.

Excitation signal optimization for minimizing fluctuations in knock out slow extraction

The synchrotron is a circular particle accelerator used for high energy physics experiments, material and life science, as well as hadron cancer therapy. After acceleration to the desired energies, particle beams are commonly extracted from the synchrotron using the method of resonant slow extraction. The goal is to deliver a steady particle flux-referred to as spill-to experiments and treatment facilities over the course of seconds while slowly emptying the storage ring. Any uncontrolled intensity fluctuations in the spill are detrimental to the efficiency of beam usage, as they lead to detector pileups or detector interlocks, hindering experiments and cancer treatment. Among the most widely used extraction scheme in medical facilities is the Radio Frequency Knock Out (RF-KO) driven resonant slow extraction, where the stored beam is transversely excited with a radio frequency (RF) field and the spill intensity is controlled by the excitation signal strength. This article presents particle dynamics simulations of the RF-KO system with the focus on finding effective mechanism for minimizing the intensity fluctuations while maintaining a good extraction efficiency and other advantages of KO extraction. An improved beam excitation signal which optimizes these main objectives is found, and is rigorously compared experimentally with other commonly applied techniques.

A perspective on tumor radiation resistance following high-LET radiation treatment

High-linear energy transfer (LET) radiation is a promising alternative to conventional low-LET radiation for therapeutic gain against cancer owing to its ability to induce complex and clustered DNA lesions. However, the development of radiation resistance poses a significant barrier. The potential molecular mechanisms that could confer resistance development are translesion synthesis (TLS), replication gap suppression (RGS) mechanisms, autophagy, epithelial-mesenchymal transition (EMT) activation, release of exosomes, and epigenetic changes. This article will discuss various types of complex clustered DNA damage, their repair mechanisms, mutagenic potential, and the development of radiation resistance strategies. Furthermore, it highlights the importance of careful consideration and patient selection when employing high-LET radiotherapy in clinical settings.

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.

Laparoscopic polyglycolic acid spacer placement for locally recurrent rectal cancer

Carbon ion radiotherapy (CIRT) has received attention for the treatment of locally recurrent rectal cancer. When the surrounding primary organs are close to the irradiation site, a spacer is required to ensure safe irradiation. This work describes a novel technique using a bioabsorbable polyglycolic acid spacer placed laparoscopically and presents a technical report with five case studies. The short-term surgical outcomes were as follows: mean operating time 235 min with blood loss of 38 mL. CIRT was planned, and the patients underwent irradiation within 2 months of surgery. No pelvic infections occurred, and all procedures were performed safely. Herein, were present a technical report with reference to a video of the surgical procedure.

Killing two birds with one stone: Abscopal effect mechanism and its application prospect in radiotherapy

Abscopal effects are characterized by the emergence of neoplasms in regions unrelated to the primary radiation therapy site, displaying a gradual attenuation or regression throughout the progression of radiation therapy, which have been of interest to scientists since Mole's proposal in 1953. The incidence of abscopal effects in radiation therapy is intricately linked to the immune system, with both innate and adaptive immune responses playing crucial roles. Biological factors impacting abscopal effects ultimately exert their influence on the intricate workings of the immune system. Although abscopal effects are rarely observed in clinical cases, the underlying mechanism remains uncertain. This article examines the biological and physical factors influencing abscopal effects of radiotherapy. Through a review of preclinical and clinical studies, this article aims to offer a comprehensive understanding of abscopal effects and proposes new avenues for future research in this field. The findings presented in this article serve as a valuable reference for researchers seeking to explore this topic in greater depth.

Relative biological effectiveness of oxygen ion beams in the rat spinal cord: Dependence on linear energy transfer and dose and comparison with model predictions

Background and purpose

Ion beams exhibit an increased relative biological effectiveness (RBE) with respect to photons. This study determined the RBE of oxygen ion beams as a function of linear energy transfer (LET) and dose in the rat spinal cord.

Materials and methods

The spinal cord of rats was irradiated at four different positions of a 6 cm spread-out Bragg-peak (LET: 26, 66, 98 and 141 keV/µm) using increasing levels of single and split oxygen ion doses. Dose-response curves were established for the endpoint paresis grade II and based on ED50 (dose at 50 % effect probability), the RBE was determined and compared to model predictions.

Results

When LET increased from 26 to 98 keV/µm, ED50 decreased from 17.2 ± 0.3 Gy to 13.5 ± 0.4 Gy for single and from 21.7 ± 0.4 Gy to 15.5 ± 0.5 Gy for split doses, however, at 141 keV/µm, ED50 rose again to 15.8 ± 0.4 Gy and 17.2 ± 0.4 Gy, respectively. As a result, the RBE increased from 1.43 ± 0.05 to 1.82 ± 0.08 (single dose) and from 1.58 ± 0.04 to 2.21 ± 0.08 (split dose), respectively, before declining again to 1.56 ± 0.06 for single and 1.99 ± 0.06 for split doses at the highest LET. Deviations from RBE-predictions were model-dependent.

Conclusion

This study established first RBE data for the late reacting central nervous system after single and split doses of oxygen ions. The data was used to validate the RBE-dependence on LET and dose of three RBE-models. This study extends the existing data base for protons, helium and carbon ions and provides important information for future patient treatments with oxygen ions.

The rationale for a carbon ion radiation therapy facility in Australia

Australia has taken a collaborative nationally networked approach to achieve particle therapy capability. This supports the under-construction proton therapy facility in Adelaide, other potential proton centres and an under-evaluation proposal for a hybrid carbon ion and proton centre in western Sydney. A wide-ranging overview is presented of the rationale for carbon ion radiation therapy, applying observations to the case for an Australian facility and to the clinical and research potential from such a national centre.

Combined ion beam irradiation platform and 3D fluorescence microscope for cellular cancer research

To improve particle radiotherapy, we need a better understanding of the biology of radiation effects, particularly in heavy ion radiation therapy, where global responses are observed despite energy deposition in only a subset of cells. Here, we integrated a high-speed swept confocally-aligned planar excitation (SCAPE) microscope into a focused ion beam irradiation platform to allow real-time 3D structural and functional imaging of living biological samples during and after irradiation. We demonstrate dynamic imaging of the acute effects of irradiation on 3D cultures of U87 human glioblastoma cells, revealing characteristic changes in cellular movement and intracellular calcium signaling following ionizing irradiation.

Kaplan lecture 2023: lymphopenia in particle therapy

PURPOSE

Lymphopenia is now generally recognized as a negative prognostic factor in radiotherapy. Already at the beginning of the century we demonstrated that high-energy carbon ions induce less damage to the lymphocytes of radiotherapy patients than X-rays, even if heavy ions are more effective per unit dose in the induction of chromosomal aberrations in blood cells irradiated ex-vivo. The explanation was based on the volume effect, i.e. the sparing of larger volumes of normal tissue in Bragg peak therapy. Here we will review the current knowledge about the difference in lymphopenia between particle and photon therapy and the consequences.

CONCLUSIONS

There is nowadays an overwhelming evidence that particle therapy reduces significantly the radiotherapy-induced lymphopenia in several tumor sites. Because lymphopenia turns down the immune response to checkpoint inhibitors, it can be predicted that particle therapy may be the ideal partner for combined radiation and immunotherapy treatment and should be selected for patients where severe lymphopenia is expected after X-rays.

Carbon-Ion Radiation Therapy for Unresectable Locally Recurrent Colorectal Cancer: A Promising Curative Treatment for Both Radiation Therapy: Naïve Cases and Reirradiation Cases

PURPOSE

It is difficult to effectively cure patients with unresectable locally recurrent colorectal cancers (LRCRCs) using conventional chemotherapy or chemoradiation therapy. Furthermore, treatment options vary depending on the patient's history of radiation therapy. Carbon-ion radiation therapy (CIRT) is a potentially curative treatment for these patients. Here, we compare the treatment outcomes of radiation therapy-naïve cases (nRT) and re-irradiation cases (reRT).

METHODS AND MATERIALS

Patients with LRCRC treated with CIRT at QST Hospital between 2003 and 2019 were eligible. CIRT was administered daily 4 d/wk for 16 fractions. The total irradiated dose was set at 73.6 Gy (relative biologic effectiveness-weighted dose [RBE]) for nRT and 70.4 Gy (RBE) for reRT patients.

RESULTS

We included 390 nRT cases and 83 reRT cases. The median follow-up period from the initiation of CIRT was 48 (5-208) months. The 3-year overall survival (OS) rates for nRT and reRT were 73% (95% CI, 68%-77%) and 76% (65%-84%), respectively. The 5-year OS rates were 50% (45%-55%) and 50% (38%-61%), respectively. These rates did not differ significantly (P = .55). The 3-year local control (LC) rates for nRT (73.6 Gy) and reRT (70.4 Gy) cases were 80% (75%-84%) and 80% (68%-88%), respectively. The 5-year LC rates were 72% (67%-78%) and 69% (55%-81%), respectively, without a significant difference (P = .56).

CONCLUSIONS

Our results suggest that CIRT for LRCRC is a very effective and promising treatment for both nRT and reRT cases.

A radiobiological perspective on radioresistance or/and radiosensitivity of head and neck squamous cell carcinoma

Background

This article aimed to compile and summarize clinically relevant literature in radiation therapy, and to discuss the potential in radioresistant and radiosensitive head and neck cancer.

Study Design

Narrative review.

Materials and methods

Google Scholar, PubMed and the Cochrane Library were retrieved using combined key words such as "radiotherapy" and "head and neck cancer". Search strings additionally queried were "radioresistant", "radiosensitive", "head and neck region", "squamous cell carcinoma", in combination with Boolean Operators 'AND' and 'OR'. Subsequently, the resulting publications were included for review of the full text.

Results

Radiotherapeutic response currently in clinical observation referred to HNSCC scoping were selected into this review. The compiled mechanisms were then detailed concerning on the clinical significance, biological characteristics, and molecular function.

Conclusions

Brachytherapy or/and external-beam radiotherapy are crucial for treating HNSCC, especially the early stage patients, but in patients with locally advanced tumors, their outcome with radiation therapy is poor due to obvious radioresistance. The curative effects mainly depend on the response of radiation therapy, so an updated review is needed to optimize further applications in HNSCC radiotherapy.