Determination of dose-response calibration curves for gamma radiation using gamma-H2AX immunofluorescence based biodosimetry.

Background: Gamma-H2AX immunofluorescence assay has gained popularity as a DNA double strand break marker. In this work, we have investigated the potential use of gamma H2AX immunofluorescence assay as a biological dosimeter for estimation of dose in our institution. Materials and methods: Seven healthy individuals were selected for the study and the blood samples collected from the first five individuals were irradiated to low doses (0-10 cGy) and high doses (50-500 cGy) in a telecobalt unit. All the samples were processed for gamma-H2AX immunofluorescence assay and the dose-response calibration curves for low and high doses were determined. In order to validate the determined dose-response calibration curves, the blood samples obtained from the sixth and seventh subjects were delivered a test dose of 7.5 cGy and 250 cGy. In addition, time and cost required to complete the assay were also reported. Results: The goodness of fit (R2) values was found to be 0.9829 and 0.9766 for low and high dose-response calibration curves. The time required to perform the gamma-H2AX immunofluorescence assay was found to be 7 hours and 30 minutes and the estimated cost per sample was 5000 rupees (~ 60 USD). Conclusion: Based on this study we conclude that the individual dose-response calibration curves determined with gamma-H2AX immunofluorescence assay for both low and high dose ranges of gamma radiation can be used for biological dosimetry. Further, the gamma-H2AX immunofluorescence assay can be used as a rapid cost-effective biodosimetric tool for institutions with an existing confocal microscope facility.

Differential network analysis reveals the key role of the ECM-receptor pathway in α-particle-induced malignant transformation.

Space particle radiation is a major environmental factor in spaceflight, and it is known to cause body damage and even trigger cancer, but with unknown molecular etiologies. To examine these causes, we developed a systems biology approach by focusing on the co-expression network analysis of transcriptomics profiles obtained from single high-dose (SE) and multiple low-dose (ME) α-particle radiation exposures of BEAS-2B human bronchial epithelial cells. First, the differential network and pathway analysis based on the global network and the core modules showed that genes in the ME group had higher enrichment for the extracellular matrix (ECM)-receptor interaction pathway. Then, collagen gene COL1A1 was screened as an important gene in the ME group assessed by network parameters and an expression study of lung adenocarcinoma samples. COL1A1 was found to promote the emergence of the neoplastic characteristics of BEAS-2B cells by both in vitro experimental analyses and in vivo immunohistochemical staining. These findings suggested that the degree of malignant transformation of cells in the ME group was greater than that of the SE, which may be caused by the dysregulation of the ECM-receptor pathway.

Experimental evidence that carbon-ion radiotherapy utilizes cytotoxic T lymphocyte-mediated anti-tumor immunity for shrinking tumors compared to X-ray therapy.

The therapeutic efficacy of radiotherapy (RT) is primarily driven by two factors: biophysical DNA damage in cancer cells and radiation-induced anti-tumor immunity. However, Anti-tumor immune responses between X-ray RT (XRT) and carbon-ion RT (CIRT) remain unclear. In this study, we, employed mouse models to assess the immunological contribution, especially cytotoxic T-lymphocyte (CTL)-mediated immunity, to the therapeutic effectiveness of XRT and CIRT in shrinking tumors. We irradiated mouse intradermal tumors of B16F10-ovalbumin (OVA) mouse melanoma cells and 3LL-OVA mouse lung cancer cells with carbon-ion beams or X-rays in the presence or absence of CTLs. CTL removal was performed by administration of anti-CD8 monoclonal antibody (mAb) in mice. Based on tumor growth delay, we determined the tumor growth and regression curves. The enhancement ratio (ER) of the slope of regression lines in the presence of CTLs, relative to the absence of CTLs, indicates the dependency of RT on CTLs for shrinking mouse tumors, and the biological effectiveness (RBE) of CIRT relative to XRT were calculated. Tumor growth curves revealed that the elimination of CD8+ CTLs by administrating anti-CD8 mAb accelerated tumor growth compared to the presence of CTLs in both RTs. The ERs were larger in CIRT compared to XRT in the B16F10-OVA tumor models, but not in the 3LL-OVA models, suggesting a greater contribution of CTL-mediated anti-tumor immunity to tumor reduction in CIRT compared to XRT in the B16F10-OVA tumor model. In addition, the RBE values for both models were larger in the presence of CTLs compared to models without CTLs, suggesting that CIRT may utilize CTL-mediated anti-tumor immunity more than X-ray. The findings from this study suggest that although immunological contribution to therapeutic efficacy may vary depending on the type of tumor cell, CIRT utilizes CTL-mediated immunity to a greater extent compared to XRT.

Pathway-based analyses of gene expression profiles at low doses of ionizing radiation.

Radiation exposure poses a significant threat to human health. Emerging research indicates that even low-dose radiation once believed to be safe, may have harmful effects. This perception has spurred a growing interest in investigating the potential risks associated with low-dose radiation exposure across various scenarios. To comprehensively explore the health consequences of low-dose radiation, our study employs a robust statistical framework that examines whether specific groups of genes, belonging to known pathways, exhibit coordinated expression patterns that align with the radiation levels. Notably, our findings reveal the existence of intricate yet consistent signatures that reflect the molecular response to radiation exposure, distinguishing between low-dose and high-dose radiation. Moreover, we leverage a pathway-constrained variational autoencoder to capture the nonlinear interactions within gene expression data. By comparing these two analytical approaches, our study aims to gain valuable insights into the impact of low-dose radiation on gene expression patterns, identify pathways that are differentially affected, and harness the potential of machine learning to uncover hidden activity within biological networks. This comparative analysis contributes to a deeper understanding of the molecular consequences of low-dose radiation exposure.

The photo-protective role of vitamin D in the microalga Emiliania huxleyi.

An essential interaction between sunlight and eukaryotes involves vitamin D production through exposure to ultraviolet (UV) radiation. While extensively studied in vertebrates, the role of vitamin D in non-animal eukaryotes like microalgae remains unclear. Here, we investigate the potential involvement of vitamin D in the UV-triggered response of Emiliania huxleyi, a microalga inhabiting shallow ocean depths that are exposed to UV. Our results show that E. huxleyi produces vitamin D2 and D3 in response to UV. We further demonstrate that E. huxleyi responds to external administration of vitamin D at the transcriptional level, regulating protective mechanisms that are also responsive to UV. Our data reveal that vitamin D addition enhances algal photosynthetic performance while reducing harmful reactive oxygen species buildup. This study contributes to understanding the function of vitamin D in E. huxleyi and its role in non-animal eukaryotes, as well as its potential importance in marine ecosystems.

Phytosanitary irradiation treatment of the aerial root mealybug, Pseudococcus baliteus (Hemiptera: Pseudococcidae).

The aerial root mealybug, Pseudococcus baliteus Lit (Hemiptera: Pseudococcidae), is an important invasive and quarantine pest that poses a potential threat to fruits, vegetables, and ornamental plants. As a result, phytosanitary treatments are necessary to ensure the commodities of international trade are free from these pests. To determine the minimum absorbed dose required for phytosanitary irradiation (PI) application, irradiation dose-response and large-scale confirmatory tests were conducted. Eggs that were 2, 4, and 6 days old and late gravid females (containing 0-day-old eggs) of P. baliteus were X-ray irradiated with doses of 10, 20, 40, 60, 80, 100, and 120 Gray (Gy). The efficacy of preventing egg-hatching (mortality) was compared using two-way ANOVA, 95% confidence interval overlapping and lethal dose ratio test in probit analysis. The radiotolerance sequence of mealybugs egg was found to be 0 < 2 ≈ 4 < 6-day-old eggs, and their estimated LD99.9968 values with 95% confidence interval were 132.0 (118.9-149.5), 137.6 (125.2-153.7), 145.5 (134.5-159.1), and 157.4 (144.6-173.6) Gy, respectively. Subsequently, target doses of 135 and 145 Gy were used in the confirmatory gamma radiation treatments. No F1 generation neonates developed from a total of 47,316 late females irradiated at the measured dose of 107.7-182.5 Gy, resulting in the treatment efficiency of 99.9937% at the 95% confidence level. Therefore, the highest dose of 183 Gy measured in the confirmatory tests is recommended as the minimum absorbed dose in PI treatment of P. baliteus for establishing national and international standards.

Terahertz technology and its applications in head and neck diseases.

The terahertz (THz) radiation refers to electromagnetic waves between infrared and millimeter waves. THz technology has shown a significant potential for medical diagnosis and biomedical applications over the past three decades. Therefore, exploring the biological effects of THz waves has become an important new field in life sciences. Specifically, THz radiation has been proved to be able to diagnose and treat several head and neck diseases. In this review, we primarily discuss the biological characteristics of THz waves and clinical applications of THz technology, focusing on the research progress of THz technology in head and neck diseases (brain cancer, hypopharyngeal cancer, oral diseases, thyroid nodules, Alzheimer's disease, eyes diseases, and otitis). The future application perspectives of THz technologies in head and neck diseases are also highlighted and proposed.

Human understandable thyroid ultrasound imaging AI report system - A bridge between AI and clinicians.

Artificial intelligence (AI) enables accurate diagnosis of thyroid cancer; however, the lack of explanation limits its application. In this study, we collected 10,021 ultrasound images from 8,079 patients across four independent institutions to develop and validate a human understandable AI report system named TiNet for thyroid cancer prediction. TiNet can extract thyroid nodule features such as texture, margin, echogenicity, shape, and location using a deep learning method conforming to the clinical diagnosis standard. Moreover, it offers excellent prediction performance (AUC 0.88) and provides quantitative explanations for the predictions. We conducted a reverse cognitive test in which clinicians matched the correct ultrasound images according to TiNet and clinical reports. The results indicated that TiNet reports (87.1% accuracy) were significantly easier to understand than clinical reports (81.6% accuracy; p < 0.001). TiNet can serve as a bridge between AI-based diagnosis and clinicians, enhancing human-AI cooperative medical decision-making.

A study of indirect action's impact on simulated neutron-induced DNA damage.

Objective.The risk of radiobiological stochastic effects associated with neutrons is strongly energy dependent. Recent Monte Carlo studies simulating neutron-irradiated nuclear DNA have demonstrated that this energy dependence is correlated with the relative biological effectiveness (RBE) of neutrons to inflict DNA damage clusters that contain difficult-to-repair double-strand breaks. However, these previous investigations were either limited to modeling direct radiation action or considered the effects of both direct and indirect action together without distinguishing between the two. In this study, we aimed to quantify the influence of indirect action in neutron irradiation scenarios and acquire novel estimations of the energy-dependent neutron RBE for inducing DNA damage clusters due to both direct and indirect action.Approach.We explored the role of indirect action in neutron-induced DNA damage by integrating a validated indirect action model into our existing simulation pipeline. Using this pipeline, we performed track-structure simulations of monoenergetic neutron irradiations (1 eV to 10 MeV) in a nuclear DNA model and analyzed the resulting simple and clustered DNA lesions. We repeated the irradiation simulations for 250 keV x-rays that acted as our reference radiation.Main results.Including indirect action significantly increased the occurrence of DNA lesions. We found that indirect action tends to amplify the damage due to direct action by inducing DNA lesions in the vicinity of directly-induced lesions, resulting in additional and larger damage clusters. Our neutron RBE results are qualitatively similar to but lower in magnitude than the established radiation protection factors and the results of previous similar investigations, due to the greater relative impact of indirect action in photon-induced damage than in neutron-induced damage.Significance.Although our model for neutron-induced DNA damage has some important limitations, our findings suggest that the energy-dependent risk of neutron-induced stochastic effects may not be completely modeled alone by the relative potential of neutrons to inflict clustered lesions via direct and indirect action in DNA damage.

Epigenetic drugs in somatostatin type 2 receptor radionuclide theranostics and radiation transcriptomics in mouse pheochromocytoma models.

Pheochromocytomas and paragangliomas (PCCs/PGLs) are catecholamine-producing tumors. In inoperable and metastatic cases, somatostatin type 2 receptor (SSTR2) expression allows for peptide receptor radionuclide therapy with [177Lu]Lu-DOTA-TATE. Insufficient receptor levels, however, limit treatment efficacy. This study evaluates whether the epigenetic drugs valproic acid (VPA) and 5-Aza-2'-deoxycytidine (DAC) modulate SSTR2 levels and sensitivity to [177Lu]Lu-DOTA-TATE in two mouse PCC models (MPC and MTT). Methods: Drug-effects on Sstr2/SSTR2 were investigated in terms of promoter methylation, mRNA and protein levels, and radiotracer binding. Radiotracer uptake was measured in subcutaneous allografts in mice using PET and SPECT imaging. Tumor growth and gene expression (RNAseq) were characterized after drug treatments. Results: DAC alone and in combination with VPA increased SSTR2 levels along with radiotracer uptake in vitro in MPC (high-SSTR2) and MTT cells (low-SSTR2). MTT but not MPC allografts responded to DAC and VPA combination with significantly elevated radiotracer uptake, although activity concentrations remained far below those in MPC tumors. In both models, combination of DAC, VPA and [177Lu]Lu-DOTA-TATE was associated with additive effects on tumor growth delay and specific transcriptional responses in gene sets involved in cancer and treatment resistance. Effects of epigenetic drugs were unrelated to CpG island methylation of the Sstr2 promoter. Conclusion: This study demonstrates that SSTR2 induction in mouse pheochromocytoma models has some therapeutic benefit that occurs via yet unknown mechanisms. Transcriptional changes in tumor allografts associated with epigenetic treatment and [177Lu]Lu-DOTA-TATE provide first insights into genetic responses of PCCs/PGLs, potentially useful for developing additional strategies to prevent tumor recurrence.

Strategies for Preclinical Studies Evaluating the Biological Effects of an Accelerator-Based Boron Neutron Capture Therapy System.

This review discusses the strategies of preclinical studies intended for accelerator-based (AB)-boron neutron capture therapy (BNCT) clinical trials, which were presented at the National Cancer Institute (NCI) Workshop on Neutron Capture Therapy held from April 20 to 22, 2022. Clinical studies of BNCT have been conducted worldwide using reactor neutron sources, with most targeting malignant brain tumors, melanoma, or head and neck cancer. Recently, small accelerator-based neutron sources that can be installed in hospitals have been developed. AB-BNCT clinical trials for recurrent malignant glioma, head and neck cancers, high-grade meningioma, melanoma, and angiosarcoma have all been conducted in Japan. The necessary methods, equipment, and facilities for preclinical studies to evaluate the biological effects of AB-BNCT systems in terms of safety and efficacy are described, with reference to two examples from Japan. The first is the National Cancer Center, which is equipped with a vertical downward neutron beam, and the other is the University of Tsukuba, which has a horizontal neutron beam. The preclinical studies discussed include cell-based assays to evaluate cytotoxicity and genotoxicity, in vivo cytotoxicity and efficacy of BNCT, and radioactivation measurements.

Short-Term Grape Consumption Diminishes UV-Induced Skin Erythema.

Over three million Americans are affected by skin cancer each year, largely as a result of exposure to sunlight. The purpose of this study was to determine the potential of grape consumption to modulate UV-induced skin erythema. With 29 human volunteers, we report that nine demonstrated greater resistance to UV irradiation of the skin after consuming the equivalent of three servings of grapes per day for two weeks. We further explored any potential relationship to the gut-skin axis. Alpha- and beta-diversity of the gut microbiome were not altered, but grape consumption modulated microbiota abundance, enzyme levels, and KEGG pathways. Striking differences in the microbiome and metabolome were discerned when comparing the nine individuals showing greater UV resistance with the 20 non-responders. Notably, three urinary metabolites, 2'-deoxyribonic acid, 3-hydroxyphenyl acetic and scyllo-inositol, were depressed in the UV-resistant group. A ROC curve revealed a 71.8% probability that measurement of urinary 2'-deoxyribonic acid identifies a UV skin non-responder. 2'-Deoxyribonic acid is cleaved from the DNA backbone by reactive oxygen species. Three of the nine subjects acquiring UV resistance following grape consumption showed a durable response, and these three demonstrated unique microbiomic and metabolomic profiles. Variable UV skin sensitivity was likely due to glutathione S-transferase polymorphisms. We conclude that a segment of the population is capable of demonstrating greater resistance to a dermal response elicited by UV irradiation as a result of grape consumption. It is uncertain if modulation of the gut-skin axis leads to enhanced UV resistance, but there is correlation. More broadly, it is reasonable to expect that these mechanisms relate to other health outcomes anticipated to result from grape consumption.

Daily irradiation versus irradiation at two- to three-day intervals in stereotactic radiotherapy for patients with 1-5 brain metastases: study protocol for a multicenter open-label randomized phase II trial.

BACKGROUND: Radiobiological daily changes within tumors are considered to be quite different between stereotactic radiotherapy (SRT) (e.g., 50 Gy in 4 fractions) and conventional radiotherapy (e.g., 60 Gy in 30 fractions). We aim to assess the optimal interval of irradiation in SRT and compare outcomes of daily irradiation with irradiation at two- to three-day intervals in SRT for patients with one to five brain metastases (BM). METHODS: This study is conducted as a multicenter open-label randomized phase II trial. Patients aged 20 or older with one to five BM, less than 3.0 cm diameter, and Karnofsky Performance Status ≥70 are eligible. A total of 70 eligible patients will be enrolled. After stratifying by the number of BMs (1, 2 vs. 3-5) and diameter of the largest tumor (< 2 cm vs. ≥ 2 cm), we randomly assigned patients (1:1) to receive daily irradiation (Arm 1), or irradiation at two- to three-day intervals (Arm 2). Both arms are performed with total dose of 27-30 Gy in 3 fractions. The primary endpoint is an intracranial local control rate, defined as intracranial local control at initially treated sites. We use a randomized phase II screening design with a two-sided α of 0∙20. The phase II trial is positive with p < 0.20. All analyses are intention to treat. This study is registered with the UMIN-clinical trials registry, number UMIN000048728. DISCUSSION: This study will provide an assessment of the impact of SRT interval on local control, survival, and toxicity for patients with 1-5 BM. The trial is ongoing and is recruiting now. TRIAL REGISTRATION: UMIN000048728. Date of registration: August 23, 2022. https://center6.umin.ac.jp/cgi-bin/ctr/ctr_view_reg.cgi?recptno=R000055515 .

Updates in combined approaches of radiotherapy and immune checkpoint inhibitors for the treatment of breast cancer.

Breast cancer is the most prevalent non-skin cancer diagnosed in females and developing novel therapeutic strategies to improve patient outcomes is crucial. The immune system plays an integral role in the body's response to breast cancer and modulating this immune response through immunotherapy is a promising therapeutic option. Although immune checkpoint inhibitors were recently approved for the treatment of breast cancer patients, not all patients respond to immune checkpoint inhibitors as a monotherapy, highlighting the need to better understand the biology underlying patient response. Additionally, as radiotherapy is a critical component of breast cancer treatment, understanding the interplay of radiation and immune checkpoint inhibitors will be vital as recent studies suggest that combined therapies may induce synergistic effects in preclinical models of breast cancer. This review will discuss the mechanisms supporting combined approaches with radiotherapy and immune checkpoint inhibitors for the treatment of breast cancer. Moreover, this review will analyze the current clinical trials examining combined approaches of radiotherapy, immunotherapy, chemotherapy, and targeted therapy. Finally, this review will evaluate data regarding treatment tolerance and potential biomarkers for these emerging therapies aimed at improving breast cancer outcomes.

Radiation-Induced Rescue Effect: Insights from Microbeam Experiments.

The present paper reviews a non-targeted effect in radiobiology known as the Radiation-Induced Rescue Effect (RIRE) and insights gained from previous microbeam experiments on RIRE. RIRE describes the mitigation of radiobiological effects in targeted irradiated cells after they receive feedback signals from co-cultured non-irradiated bystander cells, or from the medium previously conditioning those co-cultured non-irradiated bystander cells. RIRE has established or has the potential of establishing relationships with other non-traditional new developments in the fields of radiobiology, including Radiation-Induced Bystander Effect (RIBE), Radiation-Induced Field Size Effect (RIFSE) and ultra-high dose rate (FLASH) effect, which are explained. The paper first introduces RIRE, summarizes previous findings, and surveys the mechanisms proposed for observations. Unique opportunities offered by microbeam irradiations for RIRE research and some previous microbeam studies on RIRE are then described. Some thoughts on future priorities and directions of research on RIRE exploiting unique features of microbeam radiations are presented in the last section.

Effect of X-ray irradiation on development, flight, and reproduction of Spodoptera litura.

Spodoptera litura is an omnivorous pest that has spread globally. Because irradiation sterilization technology has a great potential for control of S. litura, the effect of 25-150 Gy doses of X-rays on pupal survival, flight and reproductive variables of adult moths were analyzed in this research. The X-ray irradiation with the dose of 25-150 Gy significantly affected the reproductive ability of females. Irradiating male pupae with 25-150 Gy doses of X-rays had no effect on mating, life span, or flight ability of adult moths, but significantly reduced survival and fecundity of their offspring, and the sterility rate of the F1 generation was 52.65%-99.9%. The results of logistic curve fitting showed that the sterility impact was 84% at the most appropriate irradiation dose (71.26 Gy). The sterility control was 91% in an indoor mating competition experiment when the release ratio of irradiated males (75 Gy) to nonirradiated males reached 12.6:1. The effects of X-ray irradiation doses on biological variables of S. litura and the most effective release ratio determined here provide a theoretical foundation for using radiation sterilization technology to control S. litura.

Irradiation combined with PD-L1-/- and autophagy inhibition enhances the antitumor effect of lung cancer via cGAS-STING-mediated T cell activation.

Radiotherapy combined with immune checkpoint blockade has gradually revealed the superiority in the antitumor therapy; however, the contribution of host PD-L1 remains elusive. In this study, we found that the activation of CD8+ T cells was strikingly increased in both irradiated PD-L1-expressing primary tumor and distant non-irradiated syngeneic tumor in PD-L1-deficient mouse host, and thus enhanced radiation-induced antitumor abscopal effect (ATAE) by activating cGAS-STING pathway. Notably, the autophagy inhibitors distinctively promoted dsDNA aggregation in the cytoplasm and increased the release of cGAS-STING-regulated IFN-ß from irradiated cells, which further activated bystander CD8+ T cells to release IFN-γ and contributed to ATAE. These findings revealed a signaling cascade loop that the cytokines released from irradiated tumor recruit CD8+ T cells that in turn act on the tumor cells with amplified immune responses in PD-L1-deficient host, indicating a potential sandwich therapy strategy of RT combined with PD-L1 blockage and autophagy inhibition.

Using oxygen dose histograms to quantify voxelised ultra-high dose rate (FLASH) effects in multiple radiation modalities.

Purpose.To introduce a methodology to predict tissue sparing effects in pulsed ultra-high dose rate radiation exposures which could be included in a dose-effect prediction system or treatment planning system and to illustrate it by using three published experiments.Methods and materials.The proposed system formalises the variability of oxygen levels as an oxygen dose histogram (ODH), which provides an instantaneous oxygen level at a delivered dose. The histogram concept alleviates the need for a mechanistic approach. At each given oxygen level the oxygen fixation concept is used to calculate the change in DNA-damage induction compared to the fully hypoxic case. Using the ODH concept it is possible to estimate the effect even in the case of multiple pulses, partial oxygen depletion, and spatial oxygen depletion. The system is illustrated by applying it to the seminal results by Town (Nat. 1967) on cell cultures and the pre-clinical experiment on cognitive effects by Montay-Gruelet al(2017Radiother. Oncol.124365-9).Results.The proposed system predicts that a possible FLASH-effect depends on the initial oxygenation level in tissue, the total dose delivered, pulse length and pulse repetition rate. The magnitude of the FLASH-effect is the result of a redundant system, in that it will have the same specific value for a different combination of these dependencies. The cell culture data are well represented, while a correlation between the pre-clinical experiments and the calculated values is highly significant (p < 0.01).Conclusions. A system based only on oxygen related effects is able to quantify most of the effects currently observed in FLASH-radiation.

Roadmap: helium ion therapy.

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