Best practices and novel approaches for the preclinical development of drug-radiotherapy combinations for cancer treatment.

Drug-radiation combination therapy is a practical approach to improving clinical outcomes for many tumours. Unfortunately, most clinical combination studies combine drugs with radiotherapy empirically and do not exploit mechanistic synergy in cell death and the interconnectivity of molecular pathways of tumours or rationale for selecting the dose, fractionation, and schedule, which can result in suboptimal efficacy and exacerbation of toxic effects. However, opportunities exist to generate compelling preclinical evidence for combination therapies from fit-for-purpose translational studies for simulating the intended clinical study use scenarios with standardised preclinical assays and algorithms to evaluate complex molecular interactions and analysis of synergy before clinical research. Here, we analyse and discuss the core issues in the translation of preclinical data to enhance the relevance of preclinical assays, in vitro clonogenic survival along with apoptosis, in vivo tumour regression and growth delay assays, and toxicology of organs at risk without creating barriers to innovation and provide a synopsis of emerging areas in preclinical radiobiology.

Addressing challenges in low-income and middle-income countries through novel radiotherapy research opportunities.

Although radiotherapy continues to evolve as a mainstay of the oncological armamentarium, research and innovation in radiotherapy in low-income and middle-income countries (LMICs) faces challenges. This third Series paper examines the current state of LMIC radiotherapy research and provides new data from a 2022 survey undertaken by the International Atomic Energy Agency and new data on funding. In the context of LMIC-related challenges and impediments, we explore several developments and advances-such as deep phenotyping, real-time targeting, and artificial intelligence-to flag specific opportunities with applicability and relevance for resource-constrained settings. Given the pressing nature of cancer in LMICs, we also highlight some best practices and address the broader need to develop the research workforce of the future. This Series paper thereby serves as a resource for radiation professionals.

Access to diagnostic imaging and radiotherapy technologies for patients with cancer in the Baltic countries, eastern Europe, central Asia, and the Caucasus: a comprehensive analysis.

BACKGROUND: Only 10-40% of patients with cancer in low-income and middle-income countries were able to access curative or palliative radiotherapy in 2015. We aimed to assess the current status of diagnostic imaging and radiotherapy services in the Baltic countries, eastern Europe, central Asia, and the Caucasus by collecting and analysing local data. METHODS: This Access to Radiotherapy (ART) comprehensive analysis used data from 12 countries: the three Baltic countries (Estonia, Latvia, and Lithuania), two countries in eastern Europe (Moldova and Ukraine), four countries in central Asia (Kazakhstan, Kyrgyzstan, Tajikistan, and Uzbekistan), and three countries in the Caucasus (Armenia, Azerbaijan, and Georgia), referred to here as the ART countries. We were not able to obtain engagement from Turkmenistan. The primary outcome was to update the extent of shortfalls in the availability of diagnostic imaging and radiotherapy technologies and radiotherapy human resources for patients with cancer in former Soviet Union countries. Following the methods of previous similar studies, we developed three questionnaires-targeted towards radiation oncologists, regulatory authorities, and researchers-requesting detailed information on the availability of these resources. Authors from participating countries sent two copies of the appropriate questionnaire to each of 107 identified institutions and coordinated data collection at the national level. Questionnaires were distributed in English and Russian and responses in both languages were accepted. Two virtual meetings held on May 30 and June 1, 2022, were followed by an in-person workshop held in Almaty, Kazakhstan, in September, 2022, attended by representatives from all participating countries, to discuss and further validate the data submitted up to this point. The data were collected on a dedicated web page, developed by the International Cancer Expert Corps, and were then extracted and analysed. FINDINGS: Data were collected between May 10 and Nov 30, 2022. 81 (76%) of the 107 institutions contacted, representing all 12 ART countries, submitted 167 completed questionnaires. The Baltic countries, which are defined as high-income countries, had more diagnostic imaging equipment and radiotherapy human resources (eg, Latvia [1·74] and Lithuania [1·47] have a much higher number of radiation oncologists per 100 000 population than the other ART countries, all of which had <1 radiation oncologist per 100 000 population) and greater radiotherapy technological capacities (higher numbers of linear accelerators and, similar to Georgia, high total external beam radiotherapy capacity) than the other ART countries, as well as high cancer detection rates (Latvia 311 cases per 100 000 population, Lithuania 292, and Estonia 288 vs, for example, 178 in Armenia, 144 in Ukraine, and 72 in Kazakhstan) and low cancer mortality-to-cancer incidence ratios (Estonia 0·43, Latvia 0·49, and Lithuania 0·48; lower than all but Kazakhstan [0·41]). The highest cancer mortality-to-cancer incidence ratios were reported by Moldova (0·71) and Georgia (0·74). INTERPRETATION: Our findings show that the number of cancer cases, availability of diagnostic imaging equipment, radiation oncologists and radiotherapy capacity, and cancer mortality-to-cancer incidence ratios all vary substantially across the countries studied, with the three high-income, well resourced Baltic countries performing better in all metrics than the included countries in eastern Europe, central Asia, and the Caucasus. These data highlight the challenges faced by many countries in this study, and might help to justify increased investment of financial, human, and technological resources, with the aim to improve cancer treatment outcomes. FUNDING: US Department of Energy's National Nuclear Security Administration's Office of Radiological Security.

National Cancer Institute Collaborative Workshop on Shaping the Landscape of Brain Metastases Research: challenges and recommended priorities.

Brain metastases are an increasing global public health concern, even as survival rates improve for patients with metastatic disease. Both metastases and the sequelae of their treatment are key determinants of the inter-related priorities of patient survival, function, and quality of life, mandating a multidimensional approach to clinical care and research. At a virtual National Cancer Institute Workshop in September, 2022, key stakeholders convened to define research priorities to address the crucial areas of unmet need for patients with brain metastases to achieve meaningful advances in patient outcomes. This Policy Review outlines existing knowledge gaps, collaborative opportunities, and specific recommendations regarding consensus priorities and future directions in brain metastases research. Achieving major advances in research will require enhanced coordination between the ongoing efforts of individual organisations and consortia. Importantly, the continual and active engagement of patients and patient advocates will be necessary to ensure that the directionality of all efforts reflects what is most meaningful in the context of patient care.

Biomarkers for Biodosimetry and Their Role in Predicting Radiation Injury.

Radiation-related normal tissue injury sustained during cancer radiotherapy or in a radiological or mass casualty nuclear incident is a major health concern. Reducing the risk and mitigating consequences of radiation injury could have a broad impact on cancer patients and citizens. Efforts to discover biomarkers that can determine radiation dose, predict tissue damage, and aid medical triage are underway. Exposure to ionizing radiation causes changes in gene, protein, and metabolite expression that needs to be understood to provide a holistic picture for treating acute and chronic radiation-induced toxicities. We present evidence that both RNA (mRNA, microRNA, long noncoding RNA) and metabolomic assays may provide useful biomarkers of radiation injury. RNA markers may provide information on early pathway alterations after radiation injury that can predict damage and implicate downstream targets for mitigation. In contrast, metabolomics is impacted by changes in epigenetics, genetics, and proteomics and can be considered a downstream marker that incorporates all these changes to provide an assessment of what is currently happening within an organ. We highlight research from the past 10 years to understand how biomarkers may be used to improve personalized medicine in cancer therapy and medical decision-making in mass casualty scenarios.

Long-term expression changes of immune-related genes in prostate cancer after radiotherapy.

The expression of immune-related genes in cancer cells can alter the anti-tumor immune response and thereby impact patient outcomes. Radiotherapy has been shown to modulate immune-related genes dependent on the fractionation regimen. To identify long-term changes in gene expression after irradiation, PC3 (p53 deleted) and LNCaP (p53 wildtype) prostate cancer cells were irradiated with either a single dose (SD, 10 Gy) or a fractionated regimen (MF) of 10 fractions (1 Gy per fraction). Whole human genome arrays were used to determine gene expression at 24 h and 2 months after irradiation. Immune pathway activation was analyzed with Ingenuity Pathway Analysis software. Additionally, 3D colony formation assays and T-cell cytotoxicity assays were performed. LNCaP had a higher basal expression of immunogenic genes and was more efficiently killed by cytotoxic T-cells compared to PC3. In both cell lines, MF irradiation resulted in an increase in multiple immune-related genes immediately after irradiation, while at 2 months, SD irradiation had a more pronounced effect on radiation-induced gene expression. Both immunogenic and immunosuppressive genes were upregulated in the long term in PC3 cells by a 10 Gy SD irradiation but not in LNCaP. T-cell-mediated cytotoxicity was significantly increased in 10 Gy SD PC3 cells compared to the unirradiated control and could be further enhanced by treatment with immune checkpoint inhibitors. Irradiation impacts the expression of immune-related genes in cancer cells in a fractionation-dependent manner. Understanding and targeting these changes may be a promising strategy for primary prostate cancer and recurrent tumors.

53BP1/RIF1 signaling promotes cell survival after multifractionated radiotherapy.

Multifractionated irradiation is the mainstay of radiation treatment in cancer therapy. Yet, little is known about the cellular DNA repair processes that take place between radiation fractions, even though understanding the molecular mechanisms promoting cancer cell recovery and survival could improve patient outcome and identify new avenues for targeted intervention. To address this knowledge gap, we systematically characterized how cells respond differentially to multifractionated and single-dose radiotherapy, using a combination of genetics-based and functional approaches. We found that both cancer cells and normal fibroblasts exhibited enhanced survival after multifractionated irradiation compared with an equivalent single dose of irradiation, and this effect was entirely dependent on 53BP1-mediated NHEJ. Furthermore, we identified RIF1 as the critical effector of 53BP1. Inhibiting 53BP1 recruitment to damaged chromatin completely abolished the survival advantage after multifractionated irradiation and could not be reversed by suppressing excessive end resection. Analysis of the TCGA database revealed lower expression of 53BP1 pathway genes in prostate cancer, suggesting that multifractionated radiotherapy might be a favorable option for radio-oncologic treatment in this tumor type. We propose that elucidation of DNA repair mechanisms elicited by different irradiation dosing regimens could improve radiotherapy selection for the individual patient and maximize the efficacy of radiotherapy.

Analysis of lncRNA-miRNA-mRNA expression pattern in heart tissue after total body radiation in a mouse model.

BACKGROUND: Radiation therapy is integral to effective thoracic cancer treatments, but its application is limited by sensitivity of critical organs such as the heart. The impacts of acute radiation-induced damage and its chronic effects on normal heart cells are highly relevant in radiotherapy with increasing lifespans of patients. Biomarkers for normal tissue damage after radiation exposure, whether accidental or therapeutic, are being studied as indicators of both acute and delayed effects. Recent research has highlighted the potential importance of RNAs, including messenger RNAs (mRNAs), microRNAs (miRNAs), and long non-coding RNAs (lncRNAs) as biomarkers to assess radiation damage. Understanding changes in mRNA and non-coding RNA expression will elucidate biological pathway changes after radiation. METHODS: To identify significant expression changes in mRNAs, lncRNAs, and miRNAs, we performed whole transcriptome microarray analysis of mouse heart tissue at 48 h after whole-body irradiation with 1, 2, 4, 8, and 12 Gray (Gy). We also validated changes in specific lncRNAs through RT-qPCR. Ingenuity Pathway Analysis (IPA) was used to identify pathways associated with gene expression changes. RESULTS: We observed sustained increases in lncRNAs and mRNAs, across all doses of radiation. Alas2, Aplnr, and Cxc3r1 were the most significantly downregulated mRNAs across all doses. Among the significantly upregulated mRNAs were cell-cycle arrest biomarkers Gdf15, Cdkn1a, and Ckap2. Additionally, IPA identified significant changes in gene expression relevant to senescence, apoptosis, hemoglobin synthesis, inflammation, and metabolism. LncRNAs Abhd11os, Pvt1, Trp53cor1, and Dino showed increased expression with increasing doses of radiation. We did not observe any miRNAs with sustained up- or downregulation across all doses, but miR-149-3p, miR-6538, miR-8101, miR-7118-5p, miR-211-3p, and miR-3960 were significantly upregulated after 12 Gy. CONCLUSIONS: Radiation-induced RNA expression changes may be predictive of normal tissue toxicities and may indicate targetable pathways for radiation countermeasure development and improved radiotherapy treatment plans.

National Cancer Institute support for targeted alpha-emitter therapy.

BACKGROUND: Radiopharmaceutical targeted therapy (RPT) has been studied for decades; however, recent clinical trials demonstrating efficacy have helped renewed interest in the modality. METHODS: This article reviews National Cancer Institute (NCI)'s support of RPT through communication via workshops and interest groups, through funding extramural programs in academia and small business, and through intramural research, including preclinical and clinical studies. RESULTS: NCI has co-organized workshops and organized interest groups on RPT and RPT dosimetry to encourage the community and facilitate rigorous preclinical and clinical studies. NCI has been supporting RPT research through various mechanisms. Research has been funded through peer-reviewed NCI Research and Program Grants (RPG) and NCI Small Business Innovation Research (SBIR) Development Center, which funds small business-initiated projects, some of which have led to clinical trials. The NCI Cancer Therapy Evaluation Program (CTEP)'s Radiopharmaceutical Development Initiative supports RPT in NCI-funded clinical trials, including Imaging and Radiation Oncology Core (IROC) expertise in imaging QA and dosimetry procedures. Preclinical targeted a-emitter therapy (TAT) research at the NCI's intramural program is ongoing, building on foundational work dating back to the 1980s. Ongoing "bench-to-bedside" efforts leverage the unique infrastructure of the National Institutes of Health's (NIH) Clinical Center. CONCLUSION: Given the great potential of RPT, our goal is to continue to encourage its development that will generate the high-quality evidence needed to bring this multidisciplinary treatment to patients.

United States medical preparedness for nuclear and radiological emergencies.

With the end of the Cold War in 1991, U.S. Government (USG) investments in radiation science and medical preparedness were phased out; however, the events of 11 September, which involved a terroristic attack on American soil, led to the re-establishment of funding for both radiation preparedness and development of approaches to address injuries. Similar activities have also been instituted worldwide, as the global threat of a radiological or nuclear incident continues to be a concern. Much of the USG's efforts to plan for the unthinkable have centred on establishing clear lines of communication between agencies with responsibility for triage and medical response, and external stakeholders. There have also been strong connections made between those parts of the government that establish policies, fund research, oversee regulatory approval, and purchase and stockpile necessary medical supplies. Progress made in advancing preparedness has involved a number of subject matter meetings and tabletop exercises, publication of guidance documents, assessment of available resources, clear establishment of anticipated concepts of operation for multiple radiation and nuclear scenarios, and identification/mobilization of resources. From a scientific perspective, there were clear research gaps that needed to be addressed, which included the need to identify accurate biomarkers and design biodosimetry devices to triage large numbers of civilians, develop decorporation agents that are more amenable for mass casualty use, and advance candidate products to address injuries caused by radiation exposure and thereby improve survival. Central to all these activities was the development of several different animal constructs, since efficacy testing of these approaches requires extensive work in research models that accurately simulate what would be expected in humans. Recent experiences with COVID-19 have provided an opportunity to revisit aspects of radiation preparedness, and leverage those lessons learned to enhance readiness for a possible future radiation public health emergency.

National Cancer Institute (NCI) state of the science: Targeted radiosensitizers in colorectal cancer.

Colorectal cancer (CRC) represents a major public health problem as the second leading cause of cancer-related mortality in the United States. Of an estimated 140,000 newly diagnosed CRC cases in 2018, roughly one-third of these patients will have a primary tumor located in the distal large bowel or rectum. The current standard-of-care approach includes curative-intent surgery, often after preoperative (neoadjuvant) radiotherapy (RT), to increase rates of tumor down-staging, clinical and pathologic response, as well as improving surgical resection quality. However, despite advancements in surgical techniques, as well as sharpened precision of dosimetry offered by contemporary RT delivery platforms, the oncology community continues to face challenges related to disease relapse. Ongoing investigations are aimed at testing novel radiosensitizing agents and treatments that might exploit the systemic antitumor effects of RT using immunotherapies. If successful, these treatments may usher in a new curative paradigm for rectal cancers, such that surgical interventions may be avoided. Importantly, this disease offers an opportunity to correlate matched paired biopsies, radiographic response, and molecular mechanisms of treatment sensitivity and resistance with clinical outcomes. Herein, the authors highlight the available evidence from preclinical models and early-phase studies, with an emphasis on promising developmental therapeutics undergoing prospective validation in larger scale clinical trials. This review by the National Cancer Institute's Radiation Research Program Colorectal Cancer Working Group provides an updated, comprehensive examination of the continuously evolving state of the science regarding radiosensitizer drug development in the curative treatment of CRC.

Microarray analysis of miRNA expression profiles following whole body irradiation in a mouse model.

CONTEXT: Accidental exposure to life-threatening radiation in a nuclear event is a major concern; there is an enormous need for identifying biomarkers for radiation biodosimetry to triage populations and treat critically exposed individuals. OBJECTIVE: To identify dose-differentiating miRNA signatures from whole blood samples of whole body irradiated mice. METHODS: Mice were whole body irradiated with X-rays (2 Gy-15 Gy); blood was collected at various time-points post-exposure; total RNA was isolated; miRNA microarrays were performed; miRNAs differentially expressed in irradiated vs. unirradiated controls were identified; feature extraction and classification models were applied to predict dose-differentiating miRNA signature. RESULTS: We observed a time and dose responsive alteration in the expression levels of miRNAs. Maximum number of miRNAs were altered at 24-h and 48-h time-points post-irradiation. A 23-miRNA signature was identified using feature selection algorithms and classifier models. An inverse correlation in the expression level changes of miR-17 members, and their targets were observed in whole body irradiated mice and non-human primates. CONCLUSION: Whole blood-based miRNA expression signatures might be used for predicting radiation exposures in a mass casualty nuclear incident.

Radiation-agent combinations for glioblastoma: challenges in drug development and future considerations.

Glioblastoma is an aggressive disease characterized by moderate initial response rates to first-line radiation-chemotherapy intervention followed by low poor response rates to second-line intervention. This article discusses novel strategic platforms for the development of radiation-investigational agent combination clinical trials for primary and recurrent glioblastoma in a NCI-NCTN settings with simultaneous analysis of challenges in the drug development process.

Mitigating the risk of radiation-induced cancers: limitations and paradigms in drug development.

The United States radiation medical countermeasures (MCM) programme for radiological and nuclear incidents has been focusing on developing mitigators for the acute radiation syndrome (ARS) and delayed effects of acute radiation exposure (DEARE), and biodosimetry technologies to provide radiation dose assessments for guiding treatment. Because a nuclear accident or terrorist incident could potentially expose a large number of people to low to moderate doses of ionising radiation, and thus increase their excess lifetime cancer risk, there is an interest in developing mitigators for this purpose. This article discusses the current status, issues, and challenges regarding development of mitigators against radiation-induced cancers. The challenges of developing mitigators for ARS include: the long latency between exposure and cancer manifestation, limitations of animal models, potential side effects of the mitigator itself, potential need for long-term use, the complexity of human trials to demonstrate effectiveness, and statistical power constraints for measuring health risks (and reduction of health risks after mitigation) following relatively low radiation doses (<0.75 Gy). Nevertheless, progress in the understanding of the molecular mechanisms resulting in radiation injury, along with parallel progress in dose assessment technologies, make this an opportune, if not critical, time to invest in research strategies that result in the development of agents to lower the risk of radiation-induced cancers for populations that survive a significant radiation exposure incident.

Developing an RNA Signature for Radiation Injury Using a Human Liver-on-a-Chip Model.

Radiation exposure in a therapeutic setting or during a mass casualty event requires improved medical triaging, where the time to delivery and quantity of medical countermeasures are critical to survival. Radiation-induced liver injury (RILI) and fibrosis can lead to death, but clinical symptoms manifest late in disease pathogenesis and there is no simple diagnostic test to determine RILI. Because animal models do not completely recapitulate clinical symptoms, we used a human liver-on-a-chip model to identify biomarkers of RILI. The goals of this study were: 1. to establish a microfluidic liver-on-a-chip device as a physiologically relevant model for studying radiation-induced tissue damage; and 2. to determine acute changes in RNA expression and biological pathway regulation that identify potential biomarkers and mechanisms of RILI. To model functional human liver tissue, we used the Emulate organ-on-a-chip system to establish a co-culture of human liver sinusoidal endothelial cells (LSECs) and hepatocytes. The chips were subject to 0 Gy (sham), 1 Gy, 4 Gy, or 10 Gy irradiation and cells were collected at 6 h, 24 h, or 7 days postirradiation for RNA isolation. To identify significant expression changes in messenger RNA (mRNA) and long non-coding RNA (lncRNA), we performed RNA sequencing (RNASeq) to conduct whole transcriptome analysis. We found distinct differences in expression patterns by time, dose, and cell type, with higher doses of radiation resulting in the most pronounced expression changes, as anticipated. Ingenuity Pathway Analysis indicated significant inhibition of the cell viability pathway 24 h after 10 Gy exposure in LSECs but activation of this pathway in hepatocytes, highlighting differences between cell types despite receiving the same radiation dose. Overall, hepatocytes showed fewer gene expression changes in response to radiation, with only 3 statistically significant differentially expressed genes at 7 days: APOBEC3H, PTCHD4, and GDNF. We further highlight lncRNA of interest including DINO and PURPL in hepatocytes and TMPO-AS1 and PRC-AS1 in LSECs, identifying potential biomarkers of RILI. We demonstrated the potential utility of a human liver-on-a-chip model with primary cells to model organ-specific radiation injury, establishing a model for radiation medical countermeasure development and further biomarker validation. Furthermore, we identified biomarkers that differentiate radiation dose and defined cell-specific targets for potential radiation mitigation therapies.

Whole-blood RNA biomarkers for predicting survival in non-human primates following thoracic radiation.

Radiation injury, either from radiotherapy or a mass-casualty event requires a health care system that can efficiently allocate resources to patients. We conducted a comprehensive transcriptome analysis of whole blood from a nonhuman primate model that received upper thoracic radiation (9.8-10.7 Gy). Blood samples were collected at multiple time points, extending up to 270 days post-irradiation with a minimum n = 6 for initial time points (Day 3-Day 40) and a total number of n = 28 primates. No males receiving the higher dose survived to Day 270. Using the Elastic Net model in R we found that pooling biomarkers from Day 3-21 increased our accuracy in discerning survival time, pleural effusion or dose compared to using biomarkers specific to a single day. For survival data, in predicting short term (less than 90 day), medium term (Day 91-269) or long-term survival (Day 270), prediction accuracy using only Day 3 data was 0.14 (95% Confidence Interval (CI) 0.1, 0.19) while pooled data for Male and Female was 0.76 (CI 0.69, 0.82). When pooled data was divided by biological sex, accuracy was 0.7 (CI 0.58, 0.8) for pooled data from Males and 0.84 (CI 0.76, 0.91) for Females. The development of RNA biomarkers as a tool to aid in clinical decision-making could significantly improve patient care in cases of radiation injury, whether from radiotherapy or mass-casualty events. Further validation and clinical translation of these findings could lead to improved patient care and management strategies in cases of radiation exposure.

Sex differences in radiation research.

PURPOSE: The Sex Differences in Radiation Research workshop addressed the role of sex as a confounder in radiation research and its implication in real-world radiological and nuclear applications. METHODS: In April 2022, HHS-wide partners from the Radiation and Nuclear Countermeasures Program, the Office of Research on Women's Health National Institutes of Health Office of Women's Health, U.S. Food and Drug Administration, and the Radiological and Nuclear Countermeasures Branch at the Biomedical Advanced Research and Development Authority conducted a workshop to address the scientific implication and knowledge gaps in understanding sex in basic and translational research. The goals of this workshop were to examine sex differences in 1. Radiation animal models and understand how these may affect radiation medical countermeasure development; 2. Biodosimetry and/or biomarkers used to assess acute radiation syndrome, delayed effects of acute radiation exposure, and/or predict major organ morbidities; 3. medical research that lacks representation from both sexes. In addition, regulatory policies that influence inclusion of women in research, and the gaps that exist in drug development and device clearance were discussed. Finally, real-world sex differences in human health scenarios were also considered. RESULTS: This report provides an overview of the two-day workshop, and open discussion among academic investigators, industry researchers, and U.S. government representatives. CONCLUSIONS: This meeting highlighted that current study designs lack the power to determine statistical significance based on sex, and much is unknown about the underlying factors that contribute to these differences. Investigators should accommodate both sexes in all stages of research to ensure that the outcome is robust, reproducible, and accurate, and will benefit public health.

Multiomic-Based Molecular Landscape of FaDu Xenograft Tumors in Mice after a Combinatorial Treatment with Radiation and an HSP90 Inhibitor Identifies Adaptation-Induced Targets of Resistance and Therapeutic Intervention.

Treatments involving radiation and chemotherapy alone or in combination have improved patient survival and quality of life. However, cancers frequently evade these therapies due to adaptation and tumor evolution. Given the complexity of predicting response based solely on the initial genetic profile of a patient, a predetermined treatment course may miss critical adaptation that can cause resistance or induce new targets for drug and immunotherapy. To address the timescale for these evasive mechanisms, using a mouse xenograft tumor model, we investigated the rapidity of gene expression (mRNA), molecular pathway, and phosphoproteome changes after radiation, an HSP90 inhibitor, or combination. Animals received radiation, drug, or combination treatment for 1 or 2 weeks and were then euthanized along with a time-matched untreated group for comparison. Changes in gene expression occur as early as 1 week after treatment initiation. Apoptosis and cell death pathways were activated in irradiated tumor samples. For the HSP90 inhibitor and combination treatment at weeks 1 and 2 compared with Control Day 1, gene-expression changes induced inhibition of pathways including invasion of cells, vasculogenesis, and viral infection among others. The combination group included both drug-alone and radiation-alone changes. Our data demonstrate the rapidity of gene expression and functional pathway changes in the evolving tumor as it responds to treatment. Discovering these phenotypic adaptations may help elucidate the challenges in using sustained treatment regimens and could also define evolving targets for therapeutic efficacy.

Global Workforce and Access: Demand, Education, Quality.

There has long existed a substantial disparity in access to radiotherapy globally. This issue has only been exacerbated as the growing disparity of cancer incidence between high-income countries (HIC) and low and middle-income countries (LMICs) widens, with a pronounced increase in cancer cases in LMICs. Even within HICs, iniquities within local communities may lead to a lack of access to care. Due to these trends, it is imperative to find solutions to narrow global disparities. This requires the engagement of a diverse cohort of stakeholders, including working professionals, non-governmental organizations, nonprofits, professional societies, academic and training institutions, and industry. This review brings together a diverse group of experts to highlight critical areas that could help reduce the current global disparities in radiation oncology. Advancements in technology and treatment, such as artificial intelligence, brachytherapy, hypofractionation, and digital networks, in combination with implementation science and novel funding mechanisms, offer means for increasing access to care and education globally. Common themes across sections reveal how utilizing these new innovations and strengthening collaborative efforts among stakeholders can help improve access to care globally while setting the framework for the next generation of innovations.