Accurate, Precision Radiation Medicine: A Meta-Strategy for Impacting Cancer Care, Global Health, and Nuclear Policy and Mitigating Radiation Injury From Necessary Medical Use, Space Exploration, and Potential Terrorism

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.

Inter-agency perspective: Translating advances in biomarker discovery and medical countermeasures development between terrestrial and space radiation environments

Over the past 20+ years, the U.S. Government has made significant strides in establishing research funding and initiating a portfolio consisting of subject matter experts on radiation-induced biological effects in normal tissues. Research supported by the National Cancer Institute (NCI) provided much of the early findings on identifying cellular pathways involved in radiation injuries, due to the need to push the boundaries to kill tumor cells while minimizing damage to intervening normal tissues. By protecting normal tissue surrounding the tumors, physicians can deliver a higher radiation dose to tumors and reduce adverse effects related to the treatment. Initially relying on this critical NCI research, the National Institute of Allergy and Infectious Diseases (NIAID), first tasked with developing radiation medical countermeasures in 2004, has provided bridge funding to move basic research toward advanced development and translation. The goal of the NIAID program is to fund approaches that can one day be employed to protect civilian populations during a radiological or nuclear incident. In addition, with the reality of long-term space flights and the possibility of radiation exposures to both acute, high-intensity, and chronic lower-dose levels, the National Aeronautics and Space Administration (NASA) has identified requirements to discover and develop radioprotectors and mitigators to protect their astronauts during space missions. In sustained partnership with sister agencies, these three organizations must continue to leverage funding and findings in their overlapping research areas to accelerate biomarker identification and product development to help safeguard these different and yet undeniably similar human populations - cancer patients, public citizens, and astronauts.

Predictive Radiation Oncology - A New NCI-DOE Scientific Space and Community

With a widely attended virtual kickoff event on January 29, 2021, the National Cancer Institute (NCI) and the Department of Energy (DOE) launched a series of 4 interactive, interdisciplinary workshops-and a final concluding "World Café" on March 29, 2021-focused on advancing computational approaches for predictive oncology in the clinical and research domains of radiation oncology. These events reflect 3,870 human hours of virtual engagement with representation from 8 DOE national laboratories and the Frederick National Laboratory for Cancer Research (FNL), 4 research institutes, 5 cancer centers, 17 medical schools and teaching hospitals, 5 companies, 5 federal agencies, 3 research centers, and 27 universities. Here we summarize the workshops by first describing the background for the workshops. Participants identified twelve key questions-and collaborative parallel ideas-as the focus of work going forward to advance the field. These were then used to define short-term and longer-term "Blue Sky" goals. In addition, the group determined key success factors for predictive oncology in the context of radiation oncology, if not the future of all of medicine. These are: cross-discipline collaboration, targeted talent development, development of mechanistic mathematical and computational models and tools, and access to high-quality multiscale data that bridges mechanisms to phenotype. The workshop participants reported feeling energized and highly motivated to pursue next steps together to address the unmet needs in radiation oncology specifically and in cancer research generally and that NCI and DOE project goals align at the convergence of radiation therapy and advanced computing.

Normal Tissue Injury Induced by Photon and Proton Therapies: Gaps and Opportunities

Despite technological advances in radiation therapy (RT) and cancer treatment, patients still experience adverse effects. Proton therapy (PT) has emerged as a valuable RT modality that can improve treatment outcomes. Normal tissue injury is an important determinant of the outcome; therefore, for this review, we analyzed 2 databases: (1) clinical trials registered with ClinicalTrials.gov and (2) the literature on PT in PubMed, which shows a steady increase in the number of publications. Most studies in PT registered with ClinicalTrials.gov with results available are nonrandomized early phase studies with a relatively small number of patients enrolled. From the larger database of nonrandomized trials, we listed adverse events in specific organs/sites among patients with cancer who are treated with photons and protons to identify critical issues. The present data demonstrate dosimetric advantages of PT with favorable toxicity profiles and form the basis for comparative randomized prospective trials. A comparative analysis of 3 recently completed randomized trials for normal tissue toxicities suggests that for early stage non-small cell lung cancer, no meaningful comparison could be made between stereotactic body RT and stereotactic body PT due to low accrual (NCT01511081). In addition, for locally advanced non-small cell lung cancer, a comparison of intensity modulated RTwith passive scattering PT (now largely replaced by spot-scanned intensity modulated PT), PT did not provide any benefit in normal tissue toxicity or locoregional failure over photon therapy. Finally, for locally advanced esophageal cancer, proton beam therapy provided a lower total toxicity burden but did not improve progression-free survival and quality of life (NCT01512589). The purpose of this review is to inform the limitations of current trials looking at protons and photons, considering that advances in technology, physics, and biology are a continuum, and to advocate for future trials geared toward accurate precision RT that need to be viewed as an iterative process in a defined path toward delivering optimal radiation treatment. A foundational understanding of the radiobiologic differences between protons and photons in tumor and normal tissue responses is fundamental to, and necessary for, determining the suitability of a given type of biologically optimized RT to a patient or cohort.

Moving Forward in the Next Decade: Radiation Oncology Sciences for Patient-Centered Cancer Care

In a time of rapid advances in science and technology, the opportunities for radiation oncology are undergoing transformational change. The linkage between and understanding of the physical dose and induced biological perturbations are opening entirely new areas of application. The ability to define anatomic extent of disease and the elucidation of the biology of metastases has brought a key role for radiation oncology for treating metastatic disease. That radiation can stimulate and suppress subpopulations of the immune response makes radiation a key participant in cancer immunotherapy. Targeted radiopharmaceutical therapy delivers radiation systemically with radionuclides and carrier molecules selected for their physical, chemical, and biochemical properties. Radiation oncology usage of “big data” and machine learning and artificial intelligence adds the opportunity to markedly change the workflow for clinical practice while physically targeting and adapting radiation fields in real time. Future precision targeting requires multidimensional understanding of the imaging, underlying biology, and anatomical relationship among tissues for radiation as spatial and temporal “focused biology.” Other means of energy delivery are available as are agents that can be activated by radiation with increasing ability to target treatments. With broad applicability of radiation in cancer treatment, radiation therapy is a necessity for effective cancer care, opening a career path for global health serving the medically underserved in geographically isolated populations as a substantial societal contribution addressing health disparities. Understanding risk and mitigation of radiation injury make it an important discipline for and beyond cancer care including energy policy, space exploration, national security, and global partnerships.

Radiation dose and fraction in immunotherapy: one-size regimen does not fit all settings, so how does one choose?

Recent evidence indicates that ionizing radiation can enhance immune responses to tumors. Advances in radiation delivery techniques allow hypofractionated delivery of conformal radiotherapy. Hypofractionation or other modifications of standard fractionation may improve radiation’s ability to promote immune responses to tumors. Other novel delivery options may also affect immune responses, including T-cell activation and tumor-antigen presentation changes. However, there is limited understanding of the immunological impact of hypofractionated and unique multifractionated radiotherapy regimens, as these observations are relatively recent. Hence, these differences in radiotherapy fractionation result in distinct immune-modulatory effects. Radiation oncologists and immunologists convened a virtual consensus discussion to identify current deficiencies, challenges, pitfalls and critical gaps when combining radiotherapy with immunotherapy and making recommendations to the field and advise National Cancer Institute on new directions and initiatives that will help further development of these two fields.

This commentary aims to raise the awareness of this complexity so that the need to study radiation dose, fractionation, type and volume is understood and valued by the immuno-oncology research community. Divergence of approaches and findings between preclinical studies and clinical trials highlights the need for evaluating the design of future clinical studies with particular emphasis on radiation dose and fractionation, immune biomarkers and selecting appropriate end points for combination radiation/immune modulator trials, recognizing that direct effect on the tumor and potential abscopal effect may well be different. Similarly, preclinical studies should be designed as much as possible to model the intended clinical setting. This article describes a conceptual framework for testing different radiation therapy regimens as separate models of how radiation itself functions as an immunomodulatory ‘drug’ to provide alternatives to the widely adopted ‘one-size-fits-all’ strategy of frequently used 8 Gy×3 regimens immunomodulation.

Radiation-induced Adaptive Response: New Potential for Cancer Treatment

Radiotherapy is highly effective due to its ability to physically focus the treatment to target the tumor while sparing normal tissue and its ability to be combined with systemic therapy. This systemic therapy can be utilized before radiotherapy as an adjuvant or induction treatment, during radiotherapy as a radiation "sensitizer," or following radiotherapy as a part of combined modality therapy. As part of a unique concept of using radiation as "focused biology," we investigated how tumors and normal tissues adapt to clinically relevant multifraction (MF) and single-dose (SD) radiation to observe whether the adaptations can induce susceptibility to cell killing by available drugs or by immune enhancement. We identified an adaptation occurring after MF (3 × 2 Gy) that induced cell killing when AKT-mTOR inhibitors were delivered following cessation of radiotherapy. In addition, we identified inducible changes in integrin expression 2 months following cessation of radiotherapy that differ between MF (1 Gy × 10) and SD (10 Gy) that remain targetable compared with preradiotherapy. Adaptation is reflected across different "omics" studies, and thus the range of possible molecular targets is not only broad but also time, dose, and schedule dependent. While much remains to be studied about the radiation adaptive response, radiation should be characterized by its molecular perturbations in addition to physical dose. Consideration of the adaptive effects should result in the design of a tailored radiotherapy treatment plan that accounts for specific molecular changes to be targeted as part of precision multimodality cancer treatment.

Sixteenth Annual Warren K. Sinclair Keynote Address: Frontiers in Medical Radiation Science

On the occasion of the 90 anniversary of National Council on Radiation Protection and Measurements (NCRP) and its 55 anniversary since being Congressionally Chartered, the theme of "Providing Best Answers to Your Most Pressing Questions about Radiation" is most appropriate. The question proposed here is, "What are the new frontiers for the NCRP with its breadth of talent and expertise in the rapidly evolving era of precision medicine?" Three closely related themes are presented for new applications of radiation science for research and career opportunities: (1) introduction of the new concept of defining radiation dose in biological perturbations in addition to physical dose, particularly for cancer treatment; (2) assessment of early biomarkers of radiation injury for mass casualty exposure (biodosimetry) to guide triage and for clinical application to guide radiation therapy; and (3) proposal to expand opportunities for radiation professionals, including consideration of a new training program within NCRP's "Where are the radiation professionals?" initiative that trains radiation oncologists as molecular radiation epidemiologists.

Radiation Biomarkers: Can Small Businesses Drive Accurate Radiation Precision Medicine?

Radiation therapy is an essential component of cancer treatment. Currently, tumor control and normal tissue complication probabilities derived from a general patient population guide radiation treatment. Its outcome could be improved if radiation biomarkers could be incorporated into approaches to treatment. A substantial number of cancer patients suffer from side effects of radiation therapy. These side effects can result in treatment interruption. Such unplanned treatment interruptions not only jeopardize anticancer treatment efficacy but also result in poor post-treatment quality-of-life. To develop and translate radiation biomarkers for clinical use, NCI's Radiation Research Program, in collaboration with the Small Business Innovation Research Development Center, funded four small businesses through the request for proposals after peer review during 2015-2019. Here, we summarize publicly available information on intellectual property rights, the status of development, ongoing clinical trials, success in obtaining financing and regulatory approval. An analysis of publicly available information indicates all four companies have completed phase I of SBIR funding and advanced to further development, validation and clinical trials with phase II SBIR funding. These biomarkers are: 1. A panel of genomic biomarkers of radiation response to predict toxicity and radioimmune response (MiraDx Inc., Los Angeles, CA); 2. A multiplex assay for single nucleotide polymorphism (SNP) biomarkers of radiation sensitivity to identify a subset of prostate cancer patients for which radiotherapy is contraindicated (L2 Diagnostics, New Haven, CT); 3. A cell-free DNA assay in blood to measure tissue damage shortly after radiation exposure (DiaCarta Inc., Richmond, CA); and 4. A metabolomic/lipidomic assay to predict late effects that adversely affect quality-of-life among patients treated with radiation for prostate cancer (Shuttle Pharmaceuticals, Rockville, MD). This work also provides a bird's eye view of the process of developing radiation biomarkers for use in radiation oncology clinics, some of the challenges and future directions.

Radiation-Drug Combinations to Improve Clinical Outcomes and Reduce Normal Tissue Toxicities: Current Challenges and New Approaches: Report of the Symposium Held at the 63rd Annual Meeting of the Radiation Research Society, 15-18 October 2017; Cancun, Mexico

The National Cancer Institute's (NCI) Radiation Research Program (RRP) is endeavoring to increase the relevance of preclinical research to improve outcomes of radiation therapy for cancer patients. These efforts include conducting symposia, workshops and educational sessions at annual meetings of professional societies, including the American Association of Physicists in Medicine, American Society of Radiation Oncology, Radiation Research Society (RRS), Radiosurgery Society, Society of Nuclear Medicine and Molecular Imaging, Society for Immunotherapy of Cancer and the American Association of Immunology. A symposium entitled "Radiation-Drug Combinations to Improve Clinical Outcomes and Reduce Normal Tissue Toxicities" was conducted by the NCI's RRP during the 63rd Annual Meeting of the RRS on October 16, 2017 in Cancun, Mexico. In this symposium, discussions were held to address the challenges in developing radiation-drug combinations, optimal approaches with scientific evidence to replace standard-of-care, approaches to reduce normal tissue toxicities and enhance post-treatment quality-of-life and recent advances in antibody-drug conjugates. The symposium included two broad overview talks followed by two talks illustrating examples of radiation-drug combinations under development. The overview talks identified the essential preclinical infrastructure necessary to accelerate progress in the development of evidence and important challenges in the translation of drug combinations to the clinic from the laboratory. Also addressed, in the example talks (in light of the suggested guidelines and identified challenges), were the development and translation of novel antibody drug conjugates as well as repurposing of drugs to improve efficacy and reduce normal tissue toxicities. Participation among a cross section of clinicians, scientists and scholars-in-training alike who work in this focused area highlighted the importance of continued discussions to identify and address complex challenges in this emerging area in radiation oncology.