Carbon Ion Therapy: A Modern Review of an Emerging Technology

Revolutionizing cancer treatment in India: Evaluating the unmet need, economics, and a roadmap for project implementation of particle therapy

INTRODUCTION

This study aims to quantitatively assess eligible patients and project the demand for particle therapy facilities in India from 2020 to 2040. In addition, an economic analysis evaluates the financial feasibility of implementing this technology. The study also examines the prospective benefits and challenges of adopting this technology in India.

METHODOLOGY

Cancer incidence and projected trends were analyzed for pediatric patients using the Global Childhood Cancer microsimulation model and adult patients using the Globocan data. Economic cost evaluation is performed for large-scale combined particle (carbon and proton-three room fixed-beam), large-scale proton (one gantry and two fixed-beam), and small-scale proton (one gantry) facility.

RESULTS

By 2040, the estimated number of eligible patients for particle therapy is projected to reach 161,000, including approximately 14,000 pediatric cases. The demand for particle therapy facilities is projected to rise from 81 to 97 in 2020 to 121 to 146 by 2040. The capital expenditure is estimated to be only 3.7 times that of a standard photon linear accelerator over a 30-year period. Notably, the treatment cost can be reduced to USD 400 to 800 per fraction, substantially lower than that in high-income countries (USD 1000 to 3000 per fraction).

CONCLUSION

This study indicates that, in the Indian scenario, all particle therapy models are cost-beneficial and feasible, with large-scale proton therapy being the most suitable. Despite challenges such as limited resources, space, a skilled workforce, referral systems, and patient affordability, it offers substantial benefits. These include the potential to treat many patients and convenient construction and operational costs. An iterative phased implementation strategy can effectively overcome these challenges, paving the way for the successful adoption of particle therapy in India.

PLAIN LANGUAGE SUMMARY

In India, the number of eligible patients benefiting from high-precision particle therapy technology is projected to rise till 2040. Despite high upfront costs, our study finds the long-term feasibility of all particle therapy models, potentially offering a substantial reduction in treatment cost compared to high-income countries. Despite challenges, India can succeed with an iterative phased approach.

Transcriptomic response of prostate cancer cells to carbon ion and photon irradiation with focus on androgen receptor and TP53 signaling

BACKGROUND

Radiotherapy is essential in the treatment of prostate cancer. An alternative to conventional photon radiotherapy is the application of carbon ions, which provide a superior intratumoral dose distribution and less induced damage to adjacent healthy tissue. A common characteristic of prostate cancer cells is their dependence on androgens which is exploited therapeutically by androgen deprivation therapy in the advanced prostate cancer stage. Here, we aimed to analyze the transcriptomic response of prostate cancer cells to irradiation by photons in comparison to carbon ions, focusing on DNA damage, DNA repair and androgen receptor signaling.

METHODS

Prostate cancer cell lines LNCaP (functional TP53 and androgen receptor signaling) and DU145 (dysfunctional TP53 and androgen receptor signaling) were irradiated by photons or carbon ions and the subsequent DNA damage was assessed by immuno-cytofluorescence. Furthermore, the cells were treated with an androgen-receptor agonist. The effects of irradiation and androgen treatment on the gene regulation and the transcriptome were investigated by RT-qPCR and RNA sequencing, followed by bioinformatic analysis.

RESULTS

Following photon or carbon ion irradiation, both LNCaP and DU145 cells showed a dose-dependent amount of visible DNA damage that decreased over time, indicating occurring DNA repair. In terms of gene regulation, mRNAs involved in the TP53-dependent DNA damage response were significantly upregulated by photons and carbon ions in LNCaP but not in DU145 cells, which generally showed low levels of gene regulation after irradiation. Both LNCaP and DU145 cells responded to photons and carbon ions by downregulation of genes involved in DNA repair and cell cycle, partially resembling the transcriptome response to the applied androgen receptor agonist. Neither photons nor carbon ions significantly affected canonical androgen receptor-dependent gene regulation. Furthermore, certain genes that were specifically regulated by either photon or carbon ion irradiation were identified.

CONCLUSION

Photon and carbon ion irradiation showed a significant congruence in terms of induced signaling pathways and transcriptomic responses. These responses were strongly impacted by the TP53 status. Nevertheless, irradiation mode-dependent distinct gene regulations with undefined implication for radiotherapy outcome were revealed. Androgen receptor signaling and irradiations shared regulation of certain genes with respect to DNA-repair and cell-cycle.

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.

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.

Radiation Therapy Technology Advances and Mitigation of Subsequent Neoplasms in Childhood Cancer Survivors

PURPOSE

In this Pediatric Normal Tissue Effects in the Clinic (PENTEC) vision paper, challenges and opportunities in the assessment of subsequent neoplasms (SNs) from radiation therapy (RT) are presented and discussed in the context of technology advancement.

METHODS AND MATERIALS

The paper discusses the current knowledge of SN risks associated with historic, contemporary, and future RT technologies. Opportunities for research and SN mitigation strategies in pediatric patients with cancer are reviewed.

RESULTS

Present experience with radiation carcinogenesis is from populations exposed during widely different scenarios. Knowledge gaps exist within clinical cohorts and follow-up; dose-response and volume effects; dose-rate and fractionation effects; radiation quality and proton/particle therapy; age considerations; susceptibility of specific tissues; and risks related to genetic predisposition. The biological mechanisms associated with local and patient-level risks are largely unknown.

CONCLUSIONS

Future cancer care is expected to involve several available RT technologies, necessitating evidence and strategies to assess the performance of competing treatments. It is essential to maximize the utilization of existing follow-up while planning for prospective data collection, including standardized registration of individual treatment information with linkage across patient databases.

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.

How modern treatments have modified the role of surgery in pediatric low-grade glioma

Low-grade gliomas are the most common brain tumor of childhood, and complete resection offers a high likelihood of cure. However, in many instances, tumors may not be surgically accessible without substantial morbidity, particularly in regard to gliomas arising from the optic or hypothalamic regions, as well as the brainstem. When gross total resection is not feasible, alternative treatment strategies must be considered. While conventional chemotherapy and radiation therapy have long been the backbone of adjuvant therapy for low-grade glioma, emerging techniques and technologies are rapidly changing the landscape of care for patients with this disease. This article seeks to review the current and emerging modalities of treatment for pediatric low-grade glioma.

Dosimetric study for breathing-induced motion effects in an abdominal pancreas phantom for carbon ion mini-beam radiotherapy

BACKGROUND

Particle mini-beam therapy exhibits promise in sparing healthy tissue through spatial fractionation, particularly notable for heavy ions, further enhancing the already favorable differential biological effectiveness at both target and entrance regions. However, breathing-induced organ motion affects particle mini-beam irradiation schemes since the organ displacements exceed the mini-beam structure dimensions, decreasing the advantages of spatial fractionation.

PURPOSE

In this study, the impact of breathing-induced organ motion on the dose distribution was examined at the target and organs at risk(OARs) during carbon ion mini-beam irradiation for pancreatic cancer.

METHODS

As a first step, the carbon ion mini-beam pattern was characterized with Monte Carlo simulations. To analyze the impact of breathing-induced organ motion on the dose distribution of a virtual pancreas tumor as target and related OARs, the anthropomorphic Pancreas Phantom for Ion beam Therapy (PPIeT) was irradiated with carbon ions. A mini-beam collimator was used to deliver a spatially fractionated dose distribution. During irradiation, varying breathing motion amplitudes were induced, ranging from 5 to 15 mm. Post-irradiation, the 2D dose pattern was analyzed, focusing on the full width at half maximum (FWHM), center-to-center distance (ctc), and the peak-to-valley dose ratio (PVDR).

RESULTS

The mini-beam pattern was visible within OARs, while in the virtual pancreas tumor a more homogeneous dose distribution was achieved. Applied motion affected the mini-beam pattern within the kidney, one of the OARs, reducing the PVDR from 3.78  ± $\pm$  0.12 to 1.478  ± $\pm$  0.070 for the 15 mm motion amplitude. In the immobile OARs including the spine and the skin at the back, the PVDR did not change within 3.4% comparing reference and motion conditions.

CONCLUSIONS

This study provides an initial understanding of how breathing-induced organ motion affects spatial fractionation during carbon ion irradiation, using an anthropomorphic phantom. A decrease in the PVDR was observed in the right kidney when breathing-induced motion was applied, potentially increasing the risk of damage to OARs. Therefore, further studies are needed to explore the clinical viability of mini-beam radiotherapy with carbon ions when irradiating abdominal regions.

The Use of Proton and Carbon Ion Radiation Therapy for Sarcomas

The unique physical and biological characteristics of proton and carbon ions allow for improved sparing of normal tissues, decreased integral dose to the body, and increased biological effect through high linear energy transfer. These properties are particularly useful for sarcomas given their histology, wide array of locations, and age of diagnosis. This review summarizes the literature and describes the clinical situations in which these heavy particles have advantages for treating sarcomas.

An investigation of neutron shielding and activation performances of four types of concrete for carbon ion therapy facility

Carbon ions have unique physical and biological properties that allow for precise targeting of tumors while minimizing damage to surrounding healthy tissues. The emitted neutrons dominate the radiation field in the treatment room and pose challenges for radiological shielding. Concrete is extensively utilized in the construction of radiotherapy facilities due to its good shielding characteristics, and it can be easily poured into the desired shapes and thickness. The difference in composition of concrete affects the characteristics of neutron attenuation and activation performance. Therefore, the purpose of this study is to clarify the shielding properties and activation performances of four types of concrete for carbon ion therapy facilities. The Monte Carlo method is used to analyze the neutron spectra from thick targets upon carbon ion bombardment. Furthermore, the deep attenuation efficiency of the secondary neutron in different compositions of concrete is discussed. The shielding design is developed to ensure compliance with the prescribed dose limit outside the shielding during operation. Finally, the induced radioactivity in concrete is estimated for both short-term and long-term operation. The produced radionuclides inventories and depth profiling are determined. This study reveals the shielding and radioactivity issue of carbon ion therapy facilities and is expected to aid in the design or construction of similar facilities.

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.

Clinical indications for carbon-ion radiotherapy in the UK: A critical review

INTRODUCTION

Carbon-ion radiotherapy (CIRT) has unique radiobiological properties that cause increased radiobiological effect and tumour control, especially with hypoxic tissues. This critical review aimed to evaluate clinical response to CIRT across all published tumour sites to establish if there is a clinical need for a CIRT centre in the UK.

METHODS

A critical review was performed using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Literature searching was undertaken in November 2022 within the PubMed, Science Direct, SCOPUS and Web of Science databases using the term 'carbon ion radiotherapy' in the title, abstract or author keywords.

RESULTS

After critical appraisal, data was extracted from 78 primary study papers. Strong evidence supported use of CIRT for chondrosarcoma, chordoma, nasopharyngeal, non-small cell lung cancer (NSCLC), oral cavity, prostate, rectal and salivary gland tumours. Further research is needed to strengthen the evidence base for some other tumour types.

CONCLUSION

The UK's incidence and mortality rates suggest a clinical need for CIRT for chondrosarcoma, chordoma, NSCLC, oral cavity, prostate, and rectal tumours. There is a need to improve survivorship amongst pancreatic, liver, and oesophageal cancer patients. Data published relating to CIRT for these tumours is promising but of lower quality and more research is needed in these areas.

IMPLICATIONS FOR PRACTICE

The clinical response to CIRT for certain tumours suggests the need for a carbon-ion centre in the UK. Demand for further research [phase III trials] has been identified, giving the UK opportunity to establish a research centre, with opportunity to treat, contributing to world-renowned research whilst improving patient outcomes.

The contribution of high-LET track to DNA damage formation and cell death for Monoenergy and SOBP carbon ion irradiation

Carbon ion radiotherapy (CIRT) is a heavy ion charge particle therapy with 29 years of prominent use. Despite advantages like high relative biological effectiveness (RBE), improved quality of life, and reduced treatment time, challenges persist, especially regarding heavy nuclear fragments. Our research addresses these challenges in horizontal irradiation, aiming to comprehend Monoenergetic and Spread-Out Bragg peak (SOBP) carbon ion beam trajectories using cell survival analysis and visualizing biological effects through DNA damage (γ-H2AX). This reveals repair-related protein foci near the Bragg peak. CR-39, a plastic nuclear track detector, was explored to understand high-linear energy transfer (LET) tracks and radiation quality near the Bragg peak. Findings unveil high-LET DNA damage signatures through aligned γ-H2AX foci, correlating with LET values in SOBP. CR-39 visualized high-LET particle exposure, indicating comet-type etch-pits at the Bragg peak and suggesting carbon ion fragmentation. Unexpectedly, dot-type etch-pits in irradiated and post-Bragg peak regions indicated high-LET neutron production. This investigation highlights the intricate interplay of carbon ion beams, stressing the importance of understanding LET variations, DNA damage patterns, and undesired secondary exposure.

A meta-analysis comparing efficacy and safety between proton beam therapy versus carbon ion radiotherapy

BACKGROUND

This study aimed to compare the outcomes of proton beam therapy (PBT) and carbon ion radiotherapy (CIRT) by a systematic review and meta-analysis of the existing clinical evidence.

METHODS

A systematic literature search was performed to identify studies comparing the clinical outcomes of PBT and CIRT. The included studies were required to report oncological outcomes (local control [LC], progression-free survival [PFS], or overall survival [OS]) or adverse events.

RESULTS

Eighteen articles comprising 1857 patients (947 treated with PBT and 910 treated with CIRT) were included in the analysis. The pooled analysis conducted for the overall population yielded average hazard ratios of 0.690 (95% confidence interval (CI), 0.493-0.967, p = 0.031) for LC, 0.952 (95% CI, 0.604-1.500, p = 0.590) for PFS, and 1.183 (0.872-1.607, p = 0.281) for OS with reference to CIRT. The subgroup analyses included patients treated in the head and neck, areas other than the head and neck, and patients with chordomas and chondrosarcomas. These analyses revealed no significant differences in most outcomes, except for LC in the subgroup of patients treated in areas other than the head and neck. Adverse event rates were comparable in both groups, with an odds ratio (OR) of 1.097 (95% CI, 0.744-1.616, p = 0.641). Meta-regression analysis for possible heterogeneity did not demonstrate a significant association between treatment outcomes and the ratio of biologically effective doses between modalities.

CONCLUSION

This study highlighted the comparability of PBT and CIRT in terms of oncological outcomes and adverse events.

International Consensus Statement on Allergy and Rhinology: Sinonasal Tumors

BACKGROUND

Sinonasal neoplasms, whether benign and malignant, pose a significant challenge to clinicians and represent a model area for multidisciplinary collaboration in order to optimize patient care. The International Consensus Statement on Allergy and Rhinology: Sinonasal Tumors (ICSNT) aims to summarize the best available evidence and presents 48 thematic and histopathology-based topics spanning the field.

METHODS

In accordance with prior International Consensus Statement on Allergy and Rhinology documents, ICSNT assigned each topic as an Evidence-Based Review with Recommendations, Evidence-Based Review, and Literature Review based on the level of evidence. An international group of multidisciplinary author teams were assembled for the topic reviews using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses format, and completed sections underwent a thorough and iterative consensus-building process. The final document underwent rigorous synthesis and review prior to publication.

RESULTS

The ICSNT document consists of four major sections: general principles, benign neoplasms and lesions, malignant neoplasms, and quality of life and surveillance. It covers 48 conceptual and/or histopathology-based topics relevant to sinonasal neoplasms and masses. Topics with a high level of evidence provided specific recommendations, while other areas summarized the current state of evidence. A final section highlights research opportunities and future directions, contributing to advancing knowledge and community intervention.

CONCLUSION

As an embodiment of the multidisciplinary and collaborative model of care in sinonasal neoplasms and masses, ICSNT was designed as a comprehensive, international, and multidisciplinary collaborative endeavor. Its primary objective is to summarize the existing evidence in the field of sinonasal neoplasms and masses.

Using the photon isoeffective dose formalism to compare and combine BNCT and CIRT in a head and neck tumour

Boron Neutron Capture Therapy (BNCT) is a radiotherapy technique based on the enrichment of tumour cells with suitable 10-boron concentration and on subsequent neutron irradiation. Low-energy neutron irradiation produces a localized deposition of radiation dose caused by boron neutron capture reactions. Boron is vehiculated into tumour cells via proper borated formulations, able to accumulate in the malignancy more than in normal tissues. The neutron capture releases two high-LET charged particles (i.e., an alpha particle and a lithium ion), losing their energy in a distance comparable to the average dimension of one cell. Thus BNCT is selective at the cell level and characterized by high biological effectiveness. As the radiation field is due to the interaction of neutrons with the components of biological tissues and with boron, the dosimetry requires a formalism to express the absorbed dose into photon-equivalent units. This work analyzes a clinical case of an adenoid cystic carcinoma treated with carbon-ion radiotherapy (CIRT), located close to optic nerve and deep-seated as a practical example of how to apply the formalism of BNCT photon isoeffective dose and how to evaluate the BNCT dose distribution against CIRT. The example allows presenting different dosimetrical and radiobiological quantities and drawing conclusions on the potential of BNCT stemming on the clinical result of the CIRT. The patient received CIRT with a dose constraint on the optic nerve, affecting the peripheral part of the Planning Target Volume (PTV). After the treatment, the tumour recurred in this low-dose region. BNCT was simulated for the primary tumour, with the goal to calculate the dose distribution in isoeffective units and a Tumour Control Probability (TCP) to be compared with the one of the original treatment. BNCT was then evaluated for the recurrence in the underdosed region which was not optimally covered by charged particles due to the proximity of the optic nerve. Finally, a combined treatment consisting in BNCT and carbon ion therapy was considered to show the consistency and the potential of the model. For the primary tumour, the photon isoeffective dose distribution due to BNCT was evaluated and the resulted TCP was higher than that obtained for the CIRT. The formalism produced values that are consistent with those of carbon-ion. For the recurrence, BNCT dosimetry produces a similar TCP than that of primary tumour. A combined treatment was finally simulated, showing a TCP comparable to the BNCT-alone with overall dosimetric advantage in the most peripheral parts of the treatment volume. Isoeffective dose formalism is a robust tool to analyze BNCT dosimetry and to compare it with the photon-equivalent dose calculated for carbon-ion treatment. This study introduces for the first time the possibility to combine the dosimetry obtained by two different treatment modalities, showing the potential of exploiting the cellular targeting of BNCT combined with the precision of charged particles in delivering an homogeneous dose distribution in deep-seated tumours.

Effects of nuclear interaction corrections and trichrome fragment spectra modelling on dose and linear energy transfer distributions in carbon ion radiotherapy

Background and Purpose

Nuclear interaction correction (NIC) and trichrome fragment spectra modelling improve relative biological effectiveness-weighted dose (DRBE) and dose-averaged linear energy transfer (LETd) calculation for carbon ions. The effect of those novel approaches on the clinical dose and LET distributions was investigated.

Materials and Methods

The effect of the NIC and trichrome algorithm was assessed, creating single beam plans for a virtual water phantom with standard settings and NIC + trichrome corrections. Reference DRBE and LETd distributions were simulated using FLUKA version 2021.2.9. Thirty clinically applied scanned carbon ion treatment plans were recalculated applying NIC, trichrome and NIC + trichrome corrections, using the LEM low dose approximation and compared to clinical plans (base RS). Four treatment sites were analysed: six prostate adenocarcinoma, ten head and neck, nine locally advanced pancreatic adenocarcinoma and five sacral chordoma. The FLUKA and clinical plans were compared in terms of DRBE deviations for D98%, D50%, D2% for the clinical target volume (CTV) and D50% in ring-like dose regions retrieved from isodose curves in base RS plans. Additionally, region-based median LETd deviations and global gamma parameters were evaluated.

Results

Dose deviations comparing base RS and evaluation plans were within ± 1% supported by γ-pass rates over 97% for all cases. No significant LETd deviations were reported in the CTV, but significant median LETd deviations were up to 80% for very low dose regions.

Conclusion

Our results showed improved accuracy of the predicted DRBE and LETd. Considering clinically relevant constraints, no significant modifications of clinical protocols are expected with the introduction of NIC + trichrome.

High-Linear Energy Transfer Irradiation in Clinical Carbon-Ion Beam With the Linear Energy Transfer Painting Technique for Patients With Head and Neck Cancer

Purpose

Dose-averaged linear energy transfer (LETd) is one of the important factors in determining clinical outcomes for carbon-ion radiation therapy. Innovative LET painting (LP) has been developed as an advanced form of conventional intensity modulated carbon-ion radiation therapy (IMIT) at the QST Hospital. The study had 2 motivations: to increase the minimum LETd (LETdmin) and to improve uniformity of the LETd distribution within the gross tumor volume (GTV) by using LP treatment plans for patients with head and neck cancer while maintaining the relative biologic effectiveness (RBE)-weighted dose coverage within the planning tumor volume (PTV) the same as in the conventional IMIT plan.

Methods and Materials

The LP treatment plans were designed with the in-house treatment planning system. For the plans, LETd constraints and LETdmin, goal-LETd, and maximum-LETd (LETdmax) constraints for the GTV were added to the conventional dose constraints in the IMIT prescription. For 13 patients with head and neck cancer, the RBE-weighted dose to 90% (D90) and 50% (D50) of the PTV and the LETdmin, mean (LETdmean), and LETdmax values within the GTV in the LP plans were evaluated by comparing them with those in the conventional IMIT plans.

Results

The LP for 13 patients with head and neck cancer could keep D90s and D50s for the PTV within 1.0% of those by the conventional IMIT. Among the 13 patients, the mean LETdmin of the LP plans for the GTV was 59.2 ± 7.9 keV/μm, whereas that of the IMIT plans was 45.9 ± 6.0 keV/μm. The LP increased the LETdmin to 8 to 24 keV/μm for the GTV compared with IMIT.

Conclusions

While maintaining the dose coverage to the PTV as comparable to that for IMIT, the LP increased the mean LETdmin to 13.2 keV/μm for the GTV. For a GTV up to 170 cm3, LETd > 44 keV/μm could be achieved using LP, which according to previous studies was associated with lower recurrence. In addition, the LP method delivered more uniform LETd distributions compared with IMIT.

Ion-Type Dependence of DNA Electronic Excitation in Water under Proton, α-Particle, and Carbon Ion Irradiation: A First-Principles Simulation Study

Understanding how the electronic excitation of DNA changes in response to different high-energy particles is central to advancing ion beam cancer therapy and other related approaches, such as boron neutron capture therapy. While protons have been the predominant ions of choice in ion beam cancer therapy, heavier ions, particularly carbon ions, have drawn significant attention over the past decade. Carbon ions are expected to transfer larger amounts of energy according to linear response theory. However, molecular-level details of the electronic excitation under heavier ion irradiation remain unknown. In this work, we use real-time time-dependent density functional theory simulations to examine the quantum-mechanical details of DNA electronic excitations in water under proton, α-particle, and carbon ion irradiation. Our results show that the energy transfer does indeed increase for the heavier ions, while the excitation remains highly conformal. However, the increase in the energy transfer rate, measured by electronic stopping power, does not match the prediction by the linear response model, even when accounting for the velocity dependence of the irradiating ion's charge. The simulations also reveal that while the number of holes generated on DNA increases for heavier ions, the increase is only partially responsible for the larger stopping power. Larger numbers of highly energetic holes formed from the heavier ions also contribute significantly to the increased electronic stopping power.

Effect of Linear Energy Transfer on Cystamine's Radioprotective Activity: A Study Using the Fricke Dosimeter with 6-500 MeV per Nucleon Carbon Ions-Implication for Carbon Ion Hadrontherapy

(1) Background: Radioprotective agents have garnered considerable interest due to their prospective applications in radiotherapy, public health medicine, and situations of large-scale accidental radiation exposure or impending radiological emergencies. Cystamine, an organic diamino-disulfide compound, is recognized for its radiation-protective and antioxidant properties. This study aims to utilize the aqueous ferrous sulfate (Fricke) dosimeter to measure the free-radical scavenging capabilities of cystamine during irradiation by fast carbon ions. This analysis spans an energy range from 6 to 500 MeV per nucleon, which correlates with "linear energy transfer" (LET) values ranging from approximately 248 keV/μm down to 9.3 keV/μm. (2) Methods: Monte Carlo track chemistry calculations were used to simulate the radiation-induced chemistry of aerated Fricke-cystamine solutions across a broad spectrum of cystamine concentrations, ranging from 10-6 to 1 M. (3) Results: In irradiated Fricke solutions containing cystamine, cystamine is observed to hinder the oxidation of Fe2+ ions, an effect triggered by oxidizing agents from the radiolysis of acidic water, resulting in reduced Fe3+ ion production. Our simulations, conducted both with and without accounting for the multiple ionization of water, confirm cystamine's ability to capture free radicals, highlighting its strong antioxidant properties. Aligning with prior research, our simulations also indicate that the protective and antioxidant efficiency of cystamine diminishes with increasing LET of the radiation. This result can be attributed to the changes in the geometry of the track structures when transitioning from lower to higher LETs. (4) Conclusions: If we can apply these fundamental research findings to biological systems at a physiological pH, the use of cystamine alongside carbon-ion hadrontherapy could present a promising approach to further improve the therapeutic ratio in cancer treatments.

Anti-tumor Effect of High Doses of Carbon Ions and X-Rays during Irradiation of Ehrlich Ascites Carcinoma Cells Ex Vivo

The effect of carbon ions (12C) with the energy of 400 MeV/nucleon on the dynamics of induction and growth rate of solid tumors in mice under irradiation of Ehrlich ascites carcinoma cells (EAC) ex vivo at doses of 5-30 Gy relative to the action of equally effective doses of X-ray radiation was studied. The dynamics of tumor induction under the action of 12C and X-rays had a similar character and depended on the dose during 3 months of observation. The value of the latent period, both when irradiating cells with 12C and X-ray, increased with increasing dose, and the interval for tumor induction decreased. The rate of tumor growth after ex vivo irradiation of EAC cells was independent of either dose or type of radiation. The dose at which EAC tumors are not induced within 90 days was 30 Gy for carbon ions and 60 Gy for X-rays. The value of the relative biological effectiveness of carbon ions, calculated from an equally effective dose of 50% probability of tumors, was 2.59.

High-LET charged particles: radiobiology and application for new approaches in radiotherapy

The number of patients treated with charged-particle radiotherapy as well as the number of treatment centers is increasing worldwide, particularly regarding protons. However, high-linear energy transfer (LET) particles, mainly carbon ions, are of special interest for application in radiotherapy, as their special physical features result in high precision and hence lower toxicity, and at the same time in increased efficiency in cell inactivation in the target region, i.e., the tumor. The radiobiology of high-LET particles differs with respect to DNA damage repair, cytogenetic damage, and cell death type, and their increased LET can tackle cells' resistance to hypoxia. Recent developments and perspectives, e.g., the return of high-LET particle therapy to the US with a center planned at Mayo clinics, the application of carbon ion radiotherapy using cost-reducing cyclotrons and the application of helium is foreseen to increase the interest in this type of radiotherapy. However, further preclinical research is needed to better understand the differential radiobiological mechanisms as opposed to photon radiotherapy, which will help to guide future clinical studies for optimal exploitation of high-LET particle therapy, in particular related to new concepts and innovative approaches. Herein, we summarize the basics and recent progress in high-LET particle radiobiology with a focus on carbon ions and discuss the implications of current knowledge for charged-particle radiotherapy. We emphasize the potential of high-LET particles with respect to immunogenicity and especially their combination with immunotherapy.

Radiation dose, schedule, and novel systemic targets for radio-immunotherapy combinations

Immunotherapy combinations are being investigated to expand the benefit of immune checkpoint blockade across many cancer types. Radiation combinations, in particular using stereotactic body radiotherapy, are of keen interest because of underlying mechanistic rationale, safety, and availability as a standard of care in certain cancers. In addition to direct tumor cytotoxicity, radiation therapy has immunomodulatory effects such as induction of immunogenic cell death, enhancement of antigen presentation, and expansion of the T-cell receptor repertoire as well as recruitment and increased activity of tumor-specific effector CD8+ cells. Combinations of radiation with cytokines and/or chemokines and anti-programmed death 1 and anticytotoxic T-lymphocyte antigen 4 therapies have demonstrated safety and feasibility, as well as the potential to improve long-term outcomes and possibly induce out of irradiated field or abscopal responses. Novel immunoradiotherapy combinations represent a promising therapeutic approach to overcome radioresistance and further enhance systemic immunotherapy. Potential benefits include reversing CD8+ T-cell exhaustion, inhibiting myeloid-derived suppressor cells, and reversing M2 macrophage polarization as well as decreasing levels of colony-stimulating factor-1 and transforming growth factor-β. Here, we discuss current data and mechanistic rationale for combining novel immunotherapy agents with radiation therapy.

A TOPAS model for lens-based proton radiography

Objective.Proton Radiography can be used in conjunction with proton therapy for patient positioning, real-time estimates of stopping power, and adaptive therapy in regions with motion. The modeling capability shown here can be used to evaluate lens-based radiography as an instantaneous proton-based radiographic technique. The utilization of user-friendly Monte Carlo program TOPAS enables collaborators and other users to easily conduct medical- and therapy- based simulations of the Los Alamos Neutron Science Center (LANSCE). The resulting transport model is an open-source Monte Carlo package for simulations of proton and heavy ion therapy treatments and concurrent particle imaging.Approach.The four-quadrupole, magnetic lens system of the 800-MeV proton beamline at LANSCE is modeled in TOPAS. Several imaging and contrast objects were modelled to assess transmission at energies from 230-930 MeV and different levels of particle collimation. At different proton energies, the strength of the magnetic field was scaled according toβγ,the inverse product of particle relativistic velocity and particle momentum.Main results.Materials with high atomic number, Z, (gold, gallium, bone-equivalent) generated more contrast than materials with low-Z (water, lung-equivalent, adipose-equivalent). A 5-mrad collimator was beneficial for tissue-to-contrast agent contrast, while a 10-mrad collimator was best to distinguish between different high-Z materials. Assessment with a step-wedge phantom showed water-equivalent path length did not scale directly according to predicted values but could be mapped more accurately with calibration. Poor image quality was observed at low energies (230 MeV), but improved as proton energy increased, with sub-mm resolution at 630 MeV.Significance.Proton radiography becomes viable for shallow bone structures at 330 MeV, and for deeper structures at 630 MeV. Visibility improves with use of high-Z contrast agents. This modality may be particularly viable at carbon therapy centers with accelerators capable of delivering high energy protons and could be performed with carbon therapy.

Carbon Ion Radiotherapy: An Evidence-Based Review and Summary Recommendations of Clinical Outcomes for Skull-Base Chordomas and Chondrosarcomas

Skull-base chordoma and chondrosarcoma are rare radioresistant tumors treated with surgical resection and/or radiotherapy. Because of the established dosimetric and biological benefits of heavy particle therapy, we performed a systematic and evidence-based review of the clinical outcomes of patients with skull-base chordoma and chondrosarcoma treated with carbon ion radiotherapy (CIRT). A literature review was performed using a MEDLINE search of all articles to date. We identified 227 studies as appropriate for review, and 24 were ultimately included. The published data illustrate that CIRT provides benchmark disease control outcomes for skull-base chordoma and chondrosarcoma, respectively, with acceptable toxicity. CIRT is an advanced treatment technique that may provide not only dosimetric benefits over conventional photon therapy but also biologic intensification to overcome mechanisms of radioresistance. Ongoing research is needed to define the magnitude of benefit, patient selection, and cost-effectiveness of CIRT compared to other forms of radiotherapy.

An international approach to estimating the indications and number of eligible patients for carbon ion radiation therapy (CIRT) in Australia

BACKGROUND AND PURPOSE

To establish the treatment indications and potential patient numbers for carbon ion radiation therapy (CIRT) at the proposed national carbon ion (and proton) therapy facility in the Westmead precinct, New South Wales (NSW), Australia.

METHODS

An expert panel was convened, including representatives of four operational and two proposed international carbon ion facilities, as well as NSW-based CIRT stakeholders. They met virtually to consider CIRT available evidence and experience. Information regarding Japanese CIRT was provided pre- and post- the virtual meeting. Published information for South Korea was included in discussions.

RESULTS

There was jurisdictional variation in the tumours treated by CIRT due to differing incidences of some tumours, referral patterns, differences in decisions regarding which tumours to prioritise, CIRT resources available and funding arrangements. The greatest level of consensus was reached that CIRT in Australia can be justified currently for patients with adenoid cystic carcinomas and mucosal melanomas of the head and neck, hepatocellular cancer and liver metastases, base of skull meningiomas, chordomas and chondrosarcomas. Almost 1400 Australian patients annually meet the consensus-derived indications now.

CONCLUSION

A conservative estimate is that 1% of cancer patients in Australia (or 2% of patients recommended for radiation therapy) may preferentially benefit from CIRT for initial therapy of radiation resistant tumours, or to boost persistently active disease after other therapies, or for re-irradiation of recurrent disease. On this basis, one national carbon ion facility with up to four treatment rooms is justified for Australian patients.

Simulation study of comparative dosimetric analysis of coplanar horizontal-port scanned carbon-ion beam therapy in the head and neck

OBJECTIVE

Carbon-ion radiotherapy (CIRT) has demonstrated success in treating radioresistant disease within the head and neck, owing to its unique physical and radiobiological properties. Construction cost remains prohibitive; a center offering only a horizontal port may bridge this difficulty, but removal of the vertical port may prohibit treatment of disease near critical organs-at-risk. Building a center only containing a horizontal treatment port has been proposed as one method for cost savings.

METHODS

20 complex cases of head and neck cancer previously treated with conventional CIRT were retrospectively planned using horizontal-port-only treatment incorporating non-coplanar treatment angles to achieve greater degrees of freedom. These were dosimetrically compared with the previous plans.

RESULTS

Comparable D95 coverage of both planning target volume and gross tumor volume with ability to meet organ-at-risk constraints were feasible with horizontal-port-only treatment. Collectively differences were noted in PTV D95, brain stem Dmax, contralateral eye Dmax and V10 Gy (RBE); further qualitative differences were noted on a plan-by-plan basis dependent on disease location.

CONCLUSION

Horizontal-port-only treatment employing non-coplanar angles was feasible for complicated head and neck disease typically treated with CIRT, though careful consideration is necessary on a plan-by-plan basis.

ADVANCES IN KNOWLEDGE

It is worth noting that non-coplanar approaches are not typically used with the current treatment gantry and may extend further the difference between horizontal port planning and a gantry-based gold-standard.

Evaluation of the Yield of DNA Double-Strand Breaks for Carbon Ions Using Monte Carlo Simulation and DNA Fragment Distribution

PURPOSE

The aim of this work was to provide a method to evaluate the yield of DNA double-strand breaks (DSBs) for carbon ions, overcoming the bias in existing methods due to the nonrandom distribution of DSBs.

METHODS AND MATERIALS

A previously established biophysical program based on the radiation track structure and a multilevel chromosome model was used to simulate DNA damage induced by x-rays and carbon ions. The fraction of activity retained (FAR) as a function of absorbed dose or particle fluence was obtained by counting the fraction of DNA fragments larger than 6 Mbp. Simulated FAR curves for the 250 kV x-rays and carbon ions at various energies were compared with measurements using constant-field gel electrophoresis. The doses or fluences at the FAR of 0.7 based on linear interpolation were used to estimate the simulation error for the production of DSBs.

RESULTS

The relative difference of doses at the FAR of 0.7 between simulation and experiment was -8.5% for the 250 kV x-rays. The relative differences of fluences at the FAR of 0.7 between simulations and experiments were -17.5%, -42.2%, -18.2%, -3.1%, 10.8%, and -14.5% for the 34, 65, 130, 217, 2232, and 3132 MeV carbon ions, respectively. In comparison, the measurement uncertainty was about 20%. Carbon ions produced remarkably more DSBs and DSB clusters per unit dose than x-rays. The yield of DSBs for carbon ions, ranging from 10 to 16 Gbp-1Gy-1, increased with linear energy transfer (LET) but plateaued in the high-LET end. The yield of DSB clusters first increased and then decreased with LET. This pattern was similar to the relative biological effectiveness for cell survival for heavy ions.

CONCLUSIONS

The estimated yields of DSBs for carbon ions increased from 10 Gbp-1Gy-1 in the low-LET end to 16 Gbp-1Gy-1 in the high-LET end with 20% uncertainty.

Recent advances progress in radiotherapy for breast cancer after breast-conserving surgery: a review

Adjuvant radiotherapy after breast-conserving surgery has become an integral part of the treatment of breast cancer. In recent years, the development of radiotherapy technology has made great progress in this field, including the comparison of the curative effects of various radiotherapy techniques and the performance of the segmentation times. The choice of radiotherapy technology needs to be co-determined by clinical evidence practice and evaluated for each individual patient to achieve precision radiotherapy. This article discusses the treatment effects of different radiotherapy, techniques, the risk of second cancers and short-range radiation therapy techniques after breast-conserving surgery such as hypo fractionated whole breast irradiation and accelerated partial breast irradiation. The choice of radiotherapy regimen needs to be based on the individual condition of the patient, and the general principle is to focus on the target area and reduce the irradiation of the normal tissues and organs. Short-range radiotherapy and hypofractionated are superior to conventional radiotherapy and are expected to become the mainstream treatment after breast-conserving surgery.

Particle radiotherapy for breast cancer

Breast cancer is the most common malignant tumor in female patients. Along with surgery, radiotherapy is one of the most commonly prescribed treatments for breast cancer. Over the past few decades, breast cancer radiotherapy technology has significantly improved. Nevertheless, related posttherapy complications should not be overlooked. Common complications include dose-related coronary toxicity, radiation pneumonia, and the risk of second primary cancer of the contralateral breast. Particle radiotherapy with protons or carbon ions is widely attracting interest as a potential competitor to conventional photon radiotherapy because of its superior physical and biological characteristics. This article summarizes the results of clinical research on proton and carbon-ion radiotherapy for treating breast cancer.

Selecting Optimal Proton Pencil Beam Scanning Plan Parameters to Reduce Dose Discrepancy between Discrete Spot Plan and Continuous Scanning: A Proof-of-Concept Study

Pencil beam scanning delivered with continuous scanning has several advantages over conventional discrete spot scanning. Such advantages include improved beam delivery efficiency and reduced beam delivery time. However, a move dose is delivered between consecutive spots with continuous scanning, and current treatment planning systems do not take this into account. Therefore, continuous scanning and discrete spot plans have an inherent dose discrepancy. Using the operating parameters of the state-of-the-art particle therapy system, we conducted a proof-of-concept study in which we systematically generated 28 plans for cubic targets with different combinations of plan parameters and simulated the dose discrepancies between continuous scanning and a planned one. A nomograph to guide the selection of plan parameters was developed to reduce the dose discrepancy. The effectiveness of the nomograph was evaluated with two clinical cases (one prostate and one liver). Plans with parameters guided by the nomograph decreased dose discrepancy than those used standard plan parameters. Specifically, the 2%/2 mm gamma passing rate increased from 96.3% to 100% for the prostate case and from 97.8% to 99.7% for the liver case. The CTV DVH root mean square error decreased from 2.2% to 0.2% for the prostate case and from 1.8% to 0.9% for the liver case. The decreased dose discrepancy may allow the relaxing of the delivery constraint for some cases, leading to greater benefits in continuous scanning. Further investigation is warranted.

Enhancing Immunogenicity in Metastatic Melanoma: Adjuvant Therapies to Promote the Anti-Tumor Immune Response

Advanced melanoma is an aggressive form of skin cancer characterized by low survival rates. Less than 50% of advanced melanoma patients respond to current therapies, and of those patients that do respond, many present with tumor recurrence due to resistance. The immunosuppressive tumor-immune microenvironment (TIME) remains a major obstacle in melanoma therapy. Adjuvant treatment modalities that enhance anti-tumor immune cell function are associated with improved patient response. One potential mechanism to stimulate the anti-tumor immune response is by inducing immunogenic cell death (ICD) in tumors. ICD leads to the release of damage-associated molecular patterns within the TIME, subsequently promoting antigen presentation and anti-tumor immunity. This review summarizes relevant concepts and mechanisms underlying ICD and introduces the potential of non-ablative low-intensity focused ultrasound (LOFU) as an immune-priming therapy that can be combined with ICD-inducing focal ablative therapies to promote an anti-melanoma immune response.

Ferroptosis: a novel regulated cell death participating in cellular stress response, radiotherapy, and immunotherapy

BACKGROUND

Ferroptosis is a regulated cell death mode triggered by iron-dependent toxic membrane lipid peroxidation. As a novel cell death modality that is morphologically and mechanistically different from other forms of cell death, such as apoptosis and necrosis, ferroptosis has attracted extensive attention due to its association with various diseases. Evidence on ferroptosis as a potential therapeutic strategy has accumulated with the rapid growth of research on targeting ferroptosis for tumor suppression in recent years.

METHODS

We summarize the currently known characteristics and major regulatory mechanisms of ferroptosis and present the role of ferroptosis in cellular stress responses, including ER stress and autophagy. Furthermore, we elucidate the potential applications of ferroptosis in radiotherapy and immunotherapy, which will be beneficial in exploring new strategies for clinical tumor treatment.

RESULT AND CONCLUSION

Based on specific biomarkers and precise patient-specific assessment, targeting ferroptosis has great potential to be translated into practical new approaches for clinical cancer therapy, significantly contributing to the prevention, diagnosis, prognosis, and treatment of cancer.

The Future of Radioactive Medicine

The discovery of X rays in the late 19th century heralded the beginning of a new age in medicine, and the advent of channeling the power of radiation to diagnose and treat human disease. Radiation has been leveraged in medicine in a multitude of ways and is a critical element of cancer care including screening, diagnosis, surveillance, and interventional treatments. Modern radiotherapy techniques include a multitude of methodologies utilizing both externally and internally delivered radiation from a variety of approaches. This review provides a comprehensive overview of contemporary radiotherapy methodologies, the field of radiopharmaceuticals and theranostics, effects of low dose radiation and highlights the phenomena of fear of exposure to radiation and its impact in modern medicine.

Comparing Oncologic Outcomes and Toxicity for Combined Modality Therapy vs. Carbon-Ion Radiotherapy for Previously Irradiated Locally Recurrent Rectal Cancer

No standard treatment paradigm exists for previously irradiated locally recurrent rectal cancer (PILRRC). Carbon-ion radiotherapy (CIRT) may improve oncologic outcomes and reduce toxicity compared with combined modality therapy (CMT). Eighty-five patients treated at Institution A with CIRT alone (70.4 Gy/16 fx) and eighty-six at Institution B with CMT (30 Gy/15 fx chemoradiation, resection, intraoperative electron radiotherapy (IOERT)) between 2006 and 2019 were retrospectively compared. Overall survival (OS), pelvic re-recurrence (PR), distant metastasis (DM), or any disease progression (DP) were analyzed with the Kaplan-Meier model, with outcomes compared using the Cox proportional hazards model. Acute and late toxicities were compared, as was the 2-year cost. The median time to follow-up or death was 6.5 years. Median OS in the CIRT and CMT cohorts were 4.5 and 2.6 years, respectively (p ≤ 0.01). No difference was seen in the cumulative incidence of PR (p = 0.17), DM (p = 0.39), or DP (p = 0.19). Lower acute grade ≥ 2 skin and GI/GU toxicity and lower late grade ≥ 2 GU toxicities were associated with CIRT. Higher 2-year cumulative costs were associated with CMT. Oncologic outcomes were similar for patients treated with CIRT or CMT, although patient morbidity and cost were lower with CIRT, and CIRT was associated with longer OS. Prospective comparative studies are needed.

Fluorodeoxyglucose positron emission tomography (FDG/PET) shows the effect of carbon-ion radiotherapy (CIRT); with pathologic confirmation

Response evaluation of carbon-ion radiotherapy poses a diagnostic challenge. Due to its functional aspects, fluorodeoxyglucose positron emission tomography (FDG/PET) has a role in the diagnosis of photon radiation therapy. In addition, several studies suggested that FDG/PET may be useful to select the optimal site for performing a diagnostic biopsy. Here, we report a 73-year-old female in which FDG/PET was effective in determining the recurrence of liposarcoma and the therapeutic effect. Based on the results of FDG/PET, we could make a pathologic definitive diagnosis and selectively performing carbon-ion radiotherapy for active tumors.

Acute and long-term toxicity of whole pelvis proton radiation therapy for definitive or adjuvant management of gynecologic cancers

OBJECTIVE

To characterize long-term toxicity and disease outcomes with whole pelvis (WP) pencil beam scanning proton radiation therapy (PBS PRT) for gynecologic malignancies.

METHODS

We reviewed 23 patients treated from 2013 to 2019 with WP PBS PRT for endometrial, cervical, and vaginal cancer. We report acute and late Grade (G)2+ toxicities, graded by Common Terminology Criteria for Adverse Events, Version 5. Disease outcomes were assessed by Kaplan-Meier method.

RESULTS

Median age was 59 years. Median follow up was 4.8 years. 12 (52.2%) had uterine cancer, 10 (43.5%) cervical, 1 (4.3%) vaginal. 20 (86.9%) were treated post-hysterectomy. 22 (95.7%) received chemotherapy, 12 concurrently (52.2%). The median PBS PRT dose was 50.4GyRBE (range, 45-62.5). 8 (34.8% had para-aortic/extended fields. 10 (43.5%) received brachytherapy boost. Median follow up was 4.8 years. 5-year actuarial local control was 95.2%, regional control 90.9%, distant control 74.7%, both disease control and progression-free survival 71.2%. Overall survival was 91.3%. In the acute period, 2 patients (8.7%) had G2 genitourinary (GU) toxicity, 6 (26.1%) had gastrointestinal (GI) G2-3 toxicity, 17 (73.9%) had G2-4 hematologic (H) toxicity. In the late period, 3 (13.0%) had G2 GU toxicity, 1 (4.3%) had G2 GI toxicity, 2 (8.7%) had G2-3H toxicity. The mean small bowel V15Gy was 213.4 cc. Mean large bowel V15 Gy was 131.9 cc.

CONCLUSIONS

WP PBS PRT for gynecologic malignancies delivers favorable locoregional control. Rates of GU and GI toxicity are low. Acute hematologic toxicity was most common, which may be related to the large proportion of patients receiving chemotherapy.

Relationship between the tumor microenvironment and the efficacy of the combination of radiotherapy and immunotherapy

Activating and recruiting the immune system is critical for successful cancer treatment. Since the discovery of immune checkpoint inhibitors, immunotherapy has become the standard of care for many types of cancers. However, many patients fail to respond to immunotherapy. Further research is needed to understand the mechanisms of resistance and adjuvant therapies that can help sensitize patients to immunotherapies. Here, we will discuss how radiotherapy can change the tumor microenvironment and work synergistically with immunotherapy. We will examine different pre-clinical models focusing on their limitations and their unique advantages in studying the efficacy of treatments and the tumor microenvironment. We will also describe emerging findings from clinical trials testing the combination of immunotherapy and radiotherapy.

Rotating Gantries Provide Individualized Beam Arrangements for Charged Particle Therapy

PURPOSE

This study evaluates beam angles used to generate highly individualized proton therapy treatment plans for patients eligible for carbon ion radiotherapy (CIRT).

METHODS AND MATERIALS

We retrospectively evaluated patients treated with pencil beam scanning intensity modulated proton therapy from 2015 to 2020 who had indications for CIRT. Patients were treated with a 190° rotating gantry with a robotic patient positioning system. Treatment plans were individualized to provide maximal prescription dose delivery to the tumor target volume while sparing organs at risk. The utilized beam angles were grouped, and anatomic sites with at least 10 different beam angles were sorted into histograms.

RESULTS

A total of 467 patients with 484 plans and 1196 unique beam angles were evaluated and characterized by anatomic treatment site and the number of beam angles utilized. The most common beam angles used were 0° and 180°. A wide range of beam angles were used in treating almost all anatomic sites. Only esophageal cancers had a predominantly unimodal grouping of beam angles. Pancreas cancers showed a modest grouping of beam angles.

CONCLUSIONS

The wide distribution of beam angles used to treat CIRT-eligible patients suggests that a rotating gantry is optimal to provide highly individualized beam arrangements.

Pragmatic, Prospective Comparative Effectiveness Trial of Carbon Ion Therapy, Surgery, and Proton Therapy for the Management of Pelvic Sarcomas (Soft Tissue/Bone) Involving the Bone: The PROSPER Study Rationale and Design

Surgical treatment of pelvic sarcoma involving the bone is the standard of care but is associated with several sequelae and reduced functional quality of life (QOL). Treatment with photon and proton radiotherapy is associated with relapse. Carbon ion radiotherapy (CIRT) may reduce both relapse rates and treatment sequelae. The PROSPER study is a tricontinental, nonrandomized, prospective, three-arm, pragmatic trial evaluating treatments of pelvic sarcoma involving the bone. Patients aged at least 15 years are eligible for inclusion. Participants must have an Eastern Cooperative Oncology Group Performance Status score of two or less, newly diagnosed disease, and histopathologic confirmation of pelvic chordoma, chondrosarcoma, osteosarcoma, Ewing sarcoma with bone involvement, rhabdomyosarcoma (RMS) with bone involvement, or non-RMS soft tissue sarcoma with bone involvement. Treatment arms include (1) CIRT (n = 30) delivered in Europe and Asia, (2) surgical treatment with or without adjuvant radiotherapy (n = 30), and (3) proton therapy (n = 30). Arms two and three will be conducted at Mayo Clinic campuses in Arizona, Florida, and Minnesota. The primary end point is to compare the 1-year change in functional QOL between CIRT and surgical treatment. Additional comparisons among the three arms will be made between treatment sequelae, local control, and other QOL measures.

Prompt-gamma fall-off estimation with C-ion irradiation at clinical energies, using a knife-edge slit camera: A Monte Carlo study

PURPOSE

In-vivo range verification has been a hot topic in particle therapy since two decades. Many efforts have been done for proton therapy, while fewer studies were conducted considering a beam of carbon ions. In the present work, a simulation study was performed to show whether it is possible to measure the prompt-gamma fall-off inside the high neutron background typical of carbon-ion irradiation, using a knife-edge slit camera. In addition to this, we wanted to estimate the uncertainty in retrieving the particle range in the case of a pencil beam of C-ions at clinically relevant energy of 150 MeVu.

METHODS

For these purposes, the Monte Carlo code FLUKA was adopted for simulations and three different analytical methods were implemented to get the accuracy in the range retrieval of the simulated set-up.

RESULTS

The analysis of simulation data has brought to the promising and desired precision of about 4 mm in the determination of the dose profile fall-off in case of a spill irradiation, for which all the three cited methods were coherent in their predictions.

CONCLUSIONS

The Prompt Gamma Imaging technique should be further studied as a tool to reduce range uncertainties affecting carbon ion radiation therapy.

Advances in Urological Cancer in 2022, from Basic Approaches to Clinical Management

This Special Issue includes 12 articles and 3 reviews dealing with several basic and clinical aspects of prostate, renal, and urinary tract cancer published during 2022 in Cancers, and intends to serve as a multidisciplinary chance to share the last advances in urological neoplasms [...].

Radio-fluorogenic nanoclay gel dosimeters with reduced linear energy transfer dependence for carbon-ion beam radiotherapy

PURPOSE

The precise assessment of the dose distribution of high linear energy transfer (LET) radiation remains a challenge, because the signal of most dosimeters will be saturated due to the high ionization density. Such measurements are particularly important for heavy-ion beam cancer therapy. On this basis, the present work examined the high LET effect associated with three-dimensional gel dosimetry based on radiation-induced chemical reactions. The purpose of this study was to create an ion beam radio-fluorogenic gel dosimeter with a reduced effect of LET.

METHODS

Nanoclay radio-fluorogenic gel (NC-RFG) dosimeters were prepared, typically containing 100 μM dihydrorhodamine 123 (DHR123) and 2.0 wt% nanoclay together with catalytic additives promoting Fenton or Fenton-like reactions. The radiological properties of NC-RFG dosimeters having different compositions in response to a carbon-ion beam were investigated using a fluorescence gel scanner.

RESULTS

An NC-RFG dosimeter capable of generating a fluorescence intensity distribution reflecting the carbon-ion beam dose profile was obtained. It was clarified that the reduction of the unfavorable LET dependence results from an acceleration of the reactions between DHR123 and H₂ O₂ , which is a molecular radiolysis product. The effects of varying the preparation conditions on the radiological properties of these gels were also examined. The optimum H₂ O₂ catalyst was determined to include 1 mM Fe³⁺ ions, and the addition of 100 mM pyridine was also found to increase the sensitivity.

CONCLUSIONS

This technique allows the first-ever evaluation of the depth-dose profile of a carbon-ion beam at typical therapeutic levels of several Gy without LET effect.

Radiation Therapy for Retroperitoneal Sarcomas: A Strass-Ful Situation

Locoregional recurrence (LRR) is the predominant pattern of relapse and often the cause of death in patients with retroperitoneal sarcomas (RPS). As a result, reducing LRR is a critical objective for RPS patients. However, unlike soft tissue sarcomas (STS) of the superficial trunk and extremity where the benefits of radiation therapy (RT) are well-established, the role of RT in the retroperitoneum remains controversial. Historically, preoperative or postoperative RT, either alone or in combination with intraoperative radiation (IORT), was commonly justified for RPS based on extrapolation from the superficial trunk and extremity STS literature. However, long-awaited results were recently published from the European Organization for Research and Treatment of Cancer (EORTC) STRASS study of preoperative radiotherapy plus surgery versus surgery alone for patients with RPS; there was no statistical difference in the primary endpoint of abdominal recurrence-free survival. However, several subset analyses and study limitations complicate the interpretation of the results. This review explores and contextualizes the body of evidence regarding RT's role in managing RPS.

Heavy-ion radiation-induced colitis and colorectal carcinogenesis in Il10-/- mice display co-activation of β-catenin and NF-κB signaling

Space radiation-induced gastrointestinal (GI) cancer risk models for future interplanetary astronauts are being developed that primarily rely on quantitative animal model studies to assess radiation-quality effects of heavy-ion space radiation exposure in relation to γ-rays. While current GI-cancer risk estimation efforts are focused on sporadic GI-cancer mouse models, emerging in-vivo data on heavy-ion radiation-induced long-term GI-inflammation are indicative of a higher but undetermined risk of GI-inflammation associated cancers, such as colitis-associated cancer (CAC). Therefore, we aimed to assess radiation quality effects on colonic inflammation, colon cancer incidence, and associated signaling events using an in-vivo CAC model i.e., Il10-/- mice. Male Il10-/- mice (8-10 weeks, n = 12/group) were irradiated with either sham, γ-rays or heavy-ions (28Si or 56Fe), and histopathological assessments for colitis and CAC were conducted at 2.5 months post-exposure. qPCR analysis for inflammation associated gene transcripts (Ptges and Tgfb1), and in-situ staining for markers of cell-proliferation (phospho-histone H3), oncogenesis (active-β-catenin, and cyclin D1), and inflammation (phospho-p65NF-κB, iNOS, and COX2) were performed. Significantly higher colitis and CAC frequency were noted after heavy-ion exposure, relative to γ and control mice. Higher CAC incidence after heavy-ion exposure was associated with greater activation of β-catenin and NF-κB signaling marked by induced expression of common downstream inflammatory (iNOS and COX2) and pro-proliferative (Cyclin D1) targets. In summary, IR-induced colitis and CAC incidence in Il10-/- mice depends on radiation quality and display co-activation of β-catenin and NF-κB signaling.

Particle Therapy: Clinical Applications and Biological Effects

Particle therapy is a developing area of radiotherapy, mostly involving the use of protons, neutrons and carbon ions for cancer treatment. The reduction of side effects on healthy tissues in the peritumoral area is an important advantage of particle therapy. In this review, we analyze state-of-the-art particle therapy, as compared to conventional photon therapy, to identify clinical benefits and specify the mechanisms of action on tumor cells. Systematization of published data on particle therapy confirms its successful application in a wide range of cancers and reveals a variety of biological effects which manifest at the molecular level and produce the particle therapy-specific molecular signatures. Given the rapid progress in the field, the use of particle therapy holds great promise for the near future.

Inhibition of DNA synthesis and cancer therapies

Cancer is a worldwide problem afflicting 19 million people. Inhibition of DNA synthesis has been a cornerstone of anticancer therapy. A variety of chemotherapy drugs have been developed and many of these are aimed at inhibiting DNA synthesis, as they damage DNA, form DNA adduct and interfere with DNA synthesis. Another type of chemotherapy interferes with the synthesis of nucleotide pools. There are also other types of drugs that inhibit topoisomerases resulting in the interference with DNA replication and transcription. Significant progress has been made regarding radiation therapy that includes X-ray (and γ-ray), proton therapy and heavy ion therapy. The Auger therapy is a type of radiation therapy that differs from X-ray, proton or heavy ion therapy. The method relies on the use of high Z elements such as gadolinium, iodine, gold or silver. Irradiation of these elements results in the release of electrons including the Auger electrons that have strong DNA damaging effect. Tamanoi et al. developed novel nanoparticles containing gadolinium or iodine to place high Z elements at the periphery of the nucleus thus localizing them close to DNA. Irradiation with monochromatic X-ray resulted in the formation of double-strand DNA breaks leading to the destruction of tumor mass. Comparison of conventional X-ray therapy and the Auger therapy is discussed.

Biological Mechanisms to Reduce Radioresistance and Increase the Efficacy of Radiotherapy: State of the Art

Cancer treatment with ionizing radiation (IR) is a well-established and effective clinical method to fight different types of tumors and is a palliative treatment to cure metastatic stages. Approximately half of all cancer patients undergo radiotherapy (RT) according to clinical protocols that employ two types of ionizing radiation: sparsely IR (i.e., X-rays) and densely IR (i.e., protons). Most cancer cells irradiated with therapeutic doses exhibit radio-induced cytotoxicity in terms of cell proliferation arrest and cell death by apoptosis. Nevertheless, despite the more tailored advances in RT protocols in the last few years, several tumors show a relatively high percentage of RT failure and tumor relapse due to their radioresistance. To counteract this extremely complex phenomenon and improve clinical protocols, several factors associated with radioresistance, of both a molecular and cellular nature, must be considered. Tumor genetics/epigenetics, tumor microenvironment, tumor metabolism, and the presence of non-malignant cells (i.e., fibroblast-associated cancer cells, macrophage-associated cancer cells, tumor-infiltrating lymphocytes, endothelial cells, cancer stem cells) are the main factors important in determining the tumor response to IR. Here, we attempt to provide an overview of how such factors can be taken advantage of in clinical strategies targeting radioresistant tumors.