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With the ongoing dramatic growth of radiopharmaceutical therapy, research and development in internal radiation dosimetry continue to advance both at academic medical centers and in industry. The basic paradigm for patient-specific dosimetry includes administration of a pretreatment tracer activity of the therapeutic radiopharmaceutical; measurement of its time-dependent biodistribution; definition of the pertinent anatomy; integration of the measured time-activity data to derive source-region time-integrated activities; calculation of the tumor, organ-at-risk, and/or whole-body absorbed doses; and prescription of the therapeutic administered activity. This paper provides an overview of the state of the art of patient-specific dosimetry for radiopharmaceutical therapy, including current methods and commercially available software and other resources.

The use of radiopharmaceutical therapies (RPTs) in the treatment of cancers is growing rapidly, with more agents becoming available for clinical use in last few years and many new RPTs being in development. Dosimetry assessment is critical for personalized RPT, insofar as administered activity should be assessed and optimized in order to maximize tumor-absorbed dose while keeping normal organs within defined safe dosages. However, many current clinical RPTs do not require patient-specific dosimetry based on current Food and Drug Administration-labeled approvals, and overall, dosimetry for RPT in clinical practice and trials is highly varied and underutilized. Several factors impede rigorous use of dosimetry, as compared with the more convenient and less resource-intensive practice of empiric dosing. We review various approaches to applying dosimetry for the assessment of activity in RPT and key clinical trials, the extent of dosimetry use, the relative pros and cons of dosimetry-based versus fixed activity, and practical limiting factors pertaining to current clinical practice.

Radiopharmaceutical therapies are gaining increasing prominence as they improve survival in patients with common diseases such as metastatic prostate cancer ([ 1 ][1],[ 2 ][2]). However, whereas sodium iodide (131I) therapy has been used for over 70 y in treating malignant and benign thyroid

Radiopharmaceutical targeted therapy (RPT) has been studied for decades; however, recent clinical trials demonstrating efficacy have helped renewed interest in the modality. 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. 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. 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.

Cancer heterogeneity and drug resistance limit the efficacy of cancer therapy. To address this issue, we have developed an integrated treatment protocol for effective treatment of heterogeneous ovarian cancer. Methods: An amphiphilic polymer coated magnetic iron oxide nanoparticle was conjugated with near infrared dye labeled HER2 affibody and chemotherapy drug cisplatin. The effects of the theranostic nanoparticle on targeted drug delivery, therapeutic efficacy, non-invasive magnetic resonance image (MRI)-guided therapy, and optical imaging detection of therapy resistant tumors were examined in an orthotopic human ovarian cancer xenograft model with highly heterogeneous levels of HER2 expression. Results: We found that systemic delivery of HER2-targeted magnetic iron oxide nanoparticles carrying cisplatin significantly inhibited the growth of primary tumor and peritoneal and lung metastases in the ovarian cancer xenograft model in nude mice. Differential delivery of theranostic nanoparticles into individual tumors with heterogeneous levels of HER2 expression and various responses to therapy were detectable by MRI. We further found a stronger therapeutic response in metastatic tumors compared to primary tumors, likely due to a higher level of HER2 expression and a larger number of proliferating cells in metastatic tumor cells. Relatively long-time retention of iron oxide nanoparticles in tumor tissues allowed interrogating the relationship between nanoparticle drug delivery and the presence of resistant residual tumors by in vivo molecular imaging and histological analysis of the tumor tissues. Following therapy, most of the remaining tumors were small, primary tumors that had low levels of HER2 expression and nanoparticle drug accumulation, thereby explaining their lack of therapeutic response. However, a few residual tumors had HER2-expressing tumor cells and detectable nanoparticle drug delivery but failed to respond, suggesting additional intrinsic resistant mechanisms. Nanoparticle retention in the small residual tumors, nevertheless, produced optical signals for detection by spectroscopic imaging. Conclusion: The inability to completely excise peritoneal metastatic tumors by debulking surgery as well as resistance to chemotherapy are the major clinical challenges for ovarian cancer treatment. This targeted cancer therapy has the potential for the development of effective treatment for metastatic ovarian cancer.

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.

In radiopharmaceutical therapy (RPT), a radionuclide is systemically or locally delivered with the goal of targeting and delivering radiation to cancer cells while minimizing radiation exposure to untargeted cells. Examples of current RPTs include thyroid ablation with the administration of (131)I, treatment of liver cancer with (90)Y microspheres, the treatment of bony metastases with (223)Ra and the treatment of neuroendocrine tumors with (177)Lu-DOTATATE. New RPTs are being developed where radionuclides are incorporated into systemic targeted therapies. To assure that RPT is appropriately implemented, advances in targeting need to be matched with advances in quantitative imaging and dosimetry methods. Currently, radiopharmaceutical therapy is administered by intravenous or locoregional injection and the treatment planning has typically been implemented like chemotherapy, where the activity administered is either fixed or based on a patient’s body weight or body surface area (BSA). RPT pharmacokinetics are measurable by quantitative imaging and are known to vary across patients, both in tumors and normal tissues. Therefore, fixed or weight-based activity prescriptions are not currently optimized to deliver a cytotoxic dose to targets while remaining within the tolerance dose of organs at risk. Methods that provide dose estimates to individual patients rather than to reference geometries are needed to assess and adjust the injected RPT dose. Accurate doses to targets and organs at risk will benefit the individual patients and decrease uncertainties in clinical trials. Imaging can be used to measure activity distribution in vivo and this information can be used to determine patient specific treatment plans where the dose to the targets and organs at risk can be calculated. The development and adoption of imaging-based dosimetry methods is particularly beneficial in early clinical trials. In this work we discuss dosimetric accuracy needs in modern radiation oncology, uncertainties in the dosimetry in RPT and best approaches for imaging and dosimetry of internal radionuclide therapy.

Theranostics is a new and evolving combination diagnostic and/or therapeutic approach that is demonstrating efficacy for treatment of a growing number of cancers. In this approach, a diagnostic radiopharmaceutical is used in concert with positron-emission tomography (PET) or single photon emission computed tomography (SPECT) imaging to identify whether a cancer-specific membrane protein is strongly expressed on a patient's tumors. If the molecular target is detected with sufficient specificity and uptake, a therapeutic radiopharmaceutical, nearly identical to the diagnostic radiopharmaceutical except labeled with a longer-lived alpha or beta-emitting radionuclide, is administered at a therapeutic dose level to treat the cancer. Quantitative imaging methods are being used to elucidate patient-specific pharmacokinetics to select patients for whom the therapeutic radiopharmaceutical would be most beneficial. Similarly, quantitative imaging of the therapeutic radionuclide is being used to image pharmacodynamic response to therapy (cell kill) to guide personalized, patient-specific dosages designed to both reduce radiation toxicities and optimize radiotherapeutic benefit.

Radiopharmaceuticals are reemerging as attractive anticancer agents, but there are no universally adopted guidelines or standardized procedures for evaluating agent validity before early-phase trial implementation. To validate a radiopharmaceutical, it is desirous for the radiopharmaceutical to be specific, selective, and deliverable against tumors of a given, molecularly defined cancer for which it is intended to treat. In this article, we discuss four levels of evidence—target antigen immunohistochemistry, in vitro and in vivo preclinical experiments, animal biodistribution and dosimetry studies, and first-in-human microdose biodistribution studies—that might be used to justify oncology therapeutic radiopharmaceuticals in a drug-development sequence involving early-phase trials. We discuss common practices for validating radiopharmaceuticals for clinical use, everyday pitfalls, and commonplace operationalizing steps for radiopharmaceutical early-phase trials. We anticipate in the near-term that radiopharmaceutical trials will become a larger proportion of the National Cancer Institute Cancer Therapy Evaluation Program (CTEP) portfolio.

Switch maintenance, or using alternative therapeutic agents that were not administered during a prior course of cancer treatment, has emerged as an active clinical research and regulatory agency-approvable path in the National Cancer Institute (NCI) Cancer Therapy Evaluation Program (CTEP) drug-development sequence. To better inform the design of therapeutic radiopharmaceutical trials, we reviewed academic scholarship discussing the clinical use of maintenance approaches to cancer treatment. Women with advanced-stage primary platinum-refractory or platinum-resistant ovarian carcinoma and their courses of treatment provide context for our discussion. Twenty-four (10%) out of 244 trials for women with ovarian carcinoma fit our search terms for maintenance trials. Five (2%) trials studied radiopharmaceuticals as switch maintenance. In our opinion, radiopharmaceutical switch maintenance merits further testing in prospective trials for women with advanced-stage primary platinum recurrent or refractory ovarian carcinoma.

The evaluation of antibody-targeted or peptide-targeted radiopharmaceuticals as monotherapy or in oncological drug combinations requires programmatic collaboration within the National Cancer Institute (NCI) clinical trial enterprise. Phase 0 trials provide a flexible research platform for the study of radiopharmaceutical–drug pharmacokinetics, radiation dosimetry, biomarkers of DNA damage response modulation, and pharmacodynamic benchmarks predictive of therapeutic success. In this article, we discuss a phase 0 clinical development approach for human antibody-targeted or peptide-targeted radiopharmaceutical–agent combinations. We expect that early-phase radiopharmaceutical–agent combination trials will become a more tactical and more prevalent part of radiopharmaceutical clinical development in the near-term future for the NCI Cancer Therapy Evaluation Program.

In 2018, the National Cancer Institute (NCI) and the NRG Oncology partnered for the first time to host a joint Workshop on Systemic Radiopharmaceutical Therapy (RPT) to specifically address issues and strategies of dosimetry for future clinical trials. The workshop focused on (1) current dosimetric approaches for clinical trials, (2) strategies under development that would provide optimal dose reporting, and (3) future desired/optimized approaches for the new and novel emerging radionuclides and carriers in development. In this proceedings, we review the main approaches that are applied clinically to calculate the absorbed dose: These include absorbed doses calculated over a variety of spatial scales including organ, suborgan, and voxel, all achievable within the Medical Internal Radiation Dose (MIRD) schema (S-value) can be calculated with analytic methods or Monte Carlo methods, the latter in most circumstances. This proceeding will also contrast currently available methods and tools with those used in the past, to propose a pathway whereby dosimetry helps the field by optimizing the biological effect of the treatment and trial design in the drug approval process to reduce financial and logistical costs. We will also discuss the dosimetric equivalent of biomarkers to help bring a precision medicine approach to RPT implementation-when merited by evidence collected during early-phase trial investigations. Advances in the methodology and related tools have made dosimetry the optimum biomarker for RPT.

In April 2016, the National Cancer Institute hosted a multidisciplinary workshop to discuss the current knowledge of the radiobiological aspects of charged particles used in cancer therapy to identify gaps in that knowledge that might hinder the effective clinical use of charged particles and to propose research that could help fill those gaps. The workshop was organized into 10 topics ranging from biophysical models to clinical trials and included treatment optimization, relative biological effectiveness of tumors and normal tissues, hypofractionation with particles, combination with immunotherapy, "omics," hypoxia, and particle-induced second malignancies. Given that the most commonly used charged particle in the clinic currently is protons, much of the discussion revolved around evaluating the state of knowledge and current practice of using a relative biological effectiveness of 1.1 for protons. Discussion also included the potential advantages of heavier ions, notably carbon ions, because of their increased biological effectiveness, especially for tumors frequently considered to be radiation resistant, increased effectiveness in hypoxic cells, and potential for differentially altering immune responses. The participants identified a large number of research areas in which information is needed to inform the most effective use of charged particles in the future in clinical radiation therapy. This unique form of radiation therapy holds great promise for improving cancer treatment.

For nearly 40 years, the U.S. National Cancer Institute (NCI) has funded health-related quality-of-life (HRQOL) and symptom management in oncology clinical trials as a method for including a cancer patient's experience during and after treatment. The NCI's planned scope for HRQOL, symptom and patient-reported outcomes management research is explained as it pertains to radiopharmaceutical clinical development. An effort already underway to support protocol authoring via an NCI Cancer Therapy Evaluation Program (CTEP) Centralized Protocol Writing Service (CPWS) is described as this service aids incorporation of HRQOL, symptom and patient-reported outcomes management research into sponsored protocols.

Uterine cervix cancers pose therapeutic challenges because of an overactive ribonucleotide reductase, which provides on-demand deoxyribonucleotides for DNA replication or for a DNA damage repair response. Ribonucleotide reductase overactivity bestows cancer cell resistance to the effects of radiotherapy and chemotherapy used to treat disease; but nevertheless, this same biologic overexpression provides opportune vulnerabilities relatively specific to uterine cervix cancers for new therapeutic strategies to take advantage. The discovery of human epidermal growth factor receptor 2 (ErbB2 or HER2) overexpression on metastatic uterine cervix cancer cells provides an opportunity for clinical trials of targeted radiopharmaceuticals in combination with DNA damage response modifying drugs. The National Cancer Institute's clinical trial infrastructure and its experimental therapeutics portfolio can now offer clinical trial evaluation of molecularly-targeted and tolerated radiopharmaceutical-drug combinations for women with persistent or recurrent metastatic uterine cervix cancer. This article discusses the current thinking of the National Cancer Institute in regard to attractive radiopharmaceutical strategies for this disease and others.

Targeted radiopharmaceuticals for therapeutic use deliver radionuclides directly to tumor anywhere in the body, and therefore, have renewed interest for clinical development in women with disseminated chemorefractory ovarian cancers. About two in every five women with advanced stage ovarian cancer outlive their disease after the first treatment phase, with the rest rendered incurable due to the chemorefractory nature of their disease. The National Cancer Institute (NCI) Cancer Therapy Evaluation Program conducted 67 phase I or phase Ib trials among women with relapsed or refractory ovarian cancer between 1989 and 2017 in an effort to uncover tolerable and effective drug combinations intended to increase survival rates. None of these early clinical development phase trials involved radiopharmaceuticals. Here, the NCI provides its perspective on targeted radiopharmaceutical conjugates alone or in combination with its experimental therapeutics portfolio for women with relapsed or refractory ovarian cancer. An infrastructure build for Federal radiopharmaceutical medical monitoring and adverse event reporting has begun.

Radiopharmaceuticals, meaning drugs that hold a radionuclide intended for use in cancer patients for treatment of their disease or for palliation of their disease-related symptoms, have gained new interest for clinical development in adult patients with relapsed or refractory leukemia. About one-third of adult patients outlive their leukemia, with the remainder unable to attain complete remission status following the first phase of treatment due to refractory bone marrow or blood residual microscopic disease. The National Cancer Institute (NCI) Cancer Therapy Evaluation Program conducted 49 phase 1-1b trials in adult patients with leukemia between 1986 and 2017 in an effort to discover tolerated and effective therapeutic drug combinations intended to improve remission and mortality rates. None of these trials involved radiopharmaceuticals. In this article, the NCI perspective on the challenges encountered in and on the future potential of radiopharmaceuticals alone or in combination for adult patients with relapsed or refractory leukemia is discussed. An effort is underway already to build-up the NCI's clinical trial enterprise infrastructure for radiopharmaceutical clinical development.

The Small Business Innovation Research (SBIR) and Small Business Technology Transfer (STTR) programs of the National Cancer Institute (NCI) are congressionally mandated set-aside programs that provide research funding to for-profit small businesses for the development of innovative technologies and treatments that serve the public good. These two programs have an annual budget of $159 million (in 2017) and serve as the NCI's main engine of innovation for developing and commercializing cancer technologies. In collaboration with the NCI's Radiation Research Program, the NCI SBIR Development Center published in 2015-2017 three separate requests for proposals from small businesses for the development of systemic targeted radionuclide therapy (TRT) technologies to treat cancer. TRT combines a cytotoxic radioactive isotope with a molecularly targeted agent to produce an anticancer therapy capable of treating local or systemic disease. This article summarizes the NCI SBIR funding solicitations for the development of TRTs and the research proposals funded through them.

Big data research refers to the collection and analysis of large sets of data elements and interrelationships that are difficult to process with traditional methods. It can be considered a subspecialty of the medical informatics domain under data science and analytics. This approach has been used in many areas of medicine to address topics such as clinical care and quality assessment (1–3). The need for informatics research in radiation oncology emerged as an important initiative during the 2013 National Institutes of Health (NIH)–National Cancer Institute (NCI), American Society for Radiation Oncology (ASTRO), and American Association of Physicists in Medicine (AAPM) workshop on the topic “Technology for Innovation in Radiation Oncology” (4). Our existing clinical practice generates discrete, quantitative, and structured patient-specific data (eg, images, doses, and volumes) that position us well to exploit and participate in big data initiatives. The well-established electronic infrastructure within radiation oncology should facilitate the retrieval and aggregation of much of the needed data. With additional efforts to integrate structured data collection of patient outcomes and assessments into the clinical workflow, the field of radiation oncology has a tremendous opportunity to generate large, comprehensive patient-specific data sets (5). However, there are major challenges to realizing this goal. For example, existing data are presently housed across different platforms at multiple institutions and are often not stored in a standardized manner or with common terminologies to enable pooling of data. In addition, many important data elements are not routinely discretely captured in clinical practice. There are cultural, structural, and logistical challenges (eg, computer compatibility and workflow demands) that will make the dream of big data research difficult. The big data research workshop provided a forum for leaders in cancer registries, incident report quality-assurance systems, radiogenomics, ontology of oncology, and a wide range of ongoing big data and cloud computing development projects to interact with peers in radiation oncology to develop strategies to harness data for research, quality assessment, and clinical care. The workshop provided a platform to discuss items such as data capture, data infrastructure, and protection of patient confidentiality and to improve awareness of the wide-ranging opportunities in radiation oncology, as well as to enhance the potential for research and collaboration opportunities with NIH on big data initiatives. The goals of the workshop were as follows: To discuss current and future sources of big data for use in radiation oncology research, To identify ways to improve our current data collection methods by adopting new strategies used in fields outside of radiation oncology, and To consider what new knowledge and solutions big data research can provide for clinical decision support for personalized medicine.

BACKGROUND: Clinical testing of new therapeutic interventions requires comprehensive, high-quality preclinical data. Concerns regarding quality of preclinical data have been raised in recent reports. This report examines the data on the interaction of 10 drugs with radiation and provides recommendations for improving the quality, reproducibility, and utility of future studies. The drugs were AZD6244, bortezomib, 17-DMAG, erlotinib, gefitinib, lapatinib, oxaliplatin/Lipoxal, sunitinib (Pfizer, Corporate headquarters, New York, NY), thalidomide, and vorinostat. METHODS: In vitro and in vivo data were tabulated from 125 published papers, including methods, radiation and drug doses, schedules of administration, assays, measures of interaction, presentation and interpretation of data, dosimetry, and conclusions. RESULTS: In many instances, the studies contained inadequate or unclear information that would hamper efforts to replicate or intercompare the studies, and that weakened the evidence for designing and conducting clinical trials. The published reports on these drugs showed mixed results on enhancement of radiation response, except for sunitinib, which was ineffective. CONCLUSIONS: There is a need for improved experimental design, execution, and reporting of preclinical testing of agents that are candidates for clinical use in combination with radiation. A checklist is provided for authors and reviewers to ensure that preclinical studies of drug-radiation combinations meet standards of design, execution, and interpretation, and report necessary information to ensure high quality and reproducibility of studies. Improved design, execution, common measures of enhancement, and consistent interpretation of preclinical studies of drug-radiation interactions will provide rational guidance for prioritizing drugs for clinical radiotherapy trials and for the design of such trials.

Radiopharmaceutical therapies have provided an attractive therapeutic approach since the introduction of 131I to treat thyroid cancer. New insights in cancer biology and radiochemistry have brought radiopharmaceuticals to the leading edge of oncology clinical research. National Cancer Institute (NCI) programs watch for new radiopharmaceutical breakthroughs that should be used to treat patients with unmet therapeutic needs. Such efforts occur through leveraged partnerships between NCI’s Cancer Therapy Evaluation Program and its Radiation Research Program. If groundbreaking discoveries are made, NCI pulls together clinician scientists to design novel radiopharmaceutical phase I and II monotherapy or combination trials. The specific infrastructure needs, such as radiopharmaceutical dosimetry and treatment planning, demand new programmatic workflow and regulatory oversight. This article discusses a modern approach to the development of radiopharmaceutical therapies in the era of personalized medicine.

The ability to physically target radiotherapy using image-guidance is continually improving with photons and particle therapy that include protons and heavier ions such as carbon. The unit of dose deposited is the gray (Gy); however, particle therapies produce different patterns of ionizations, and

In 2013, the Society of Nuclear Medicine and Molecular Imaging (SNMMI) and the National Cancer Institute (NCI) partnered for the first time to host a joint workshop on targeted radionuclide therapy (TRT) ([1][1]). Broad discussion at that gathering suggested the need for a follow-up workshop

Purpose To summarize important talking points from a 2016 symposium focusing on real-world challenges to advancing precision medicine in radiation oncology, and to help radiation oncologists navigate the practical challenges of precision, radiation oncology. Methods and Materials The American Society for Radiation Oncology, American Association of Physicists in Medicine, and National Cancer Institute cosponsored a meeting on precision medicine in radiation oncology. In June 2016 numerous scientists, clinicians, and physicists convened at the National Institutes of Health to discuss challenges and future directions toward personalized radiation therapy. Various breakout sessions were held to discuss particular components and approaches to the implementation of personalized radiation oncology. This article summarizes the genomically guided radiation therapy breakout session. Results A summary of existing genomic data enabling personalized radiation therapy, ongoing clinical trials, current challenges, and future directions was collected. The group attempted to provide both a current overview of data that radiation oncologists could use to personalize therapy, along with data that are anticipated in the coming years. It seems apparent from the provided review that a considerable opportunity exists to truly bring genomically guided radiation therapy into clinical reality. Conclusions Genomically guided radiation therapy is a necessity that must be embraced in the coming years. Incorporating these data into treatment recommendations will provide radiation oncologists with a substantial opportunity to improve outcomes for numerous cancer patients. More research focused on this topic is needed to bring genomic signatures into routine standard of care.

The growing interest in targeted radionuclide therapy (TRT) for a broad range of applications is shared by a diverse group of medical professionals, including but not limited to physicians and basic scientists in several fields, as well as members of industry, regulatory bodies, and patients.

Despite advances in cancer diagnosis and treatment, ovarian cancer remains one of the most fatal cancer types. The development of targeted nanoparticle imaging probes and therapeutics offers promising approaches for early detection and effective treatment of ovarian cancer. In this study, we have developed HER-2 targeted magnetic iron oxide nanoparticles (IONPs) by conjugating a high affinity and small size HER-2 affibody that is labeled with a unique near infrared dye (NIR-830) to the nanoparticles. Using a clinically relevant orthotopic human ovarian tumor xenograft model, we have shown that HER-2 targeted IONPs are selectively delivered into both primary and disseminated ovarian tumors, enabling non-invasive optical and MR imaging of the tumors as small as 1 mm in the peritoneal cavity. We have determined that HER-2 targeted delivery of the IONPs is essential for specific and sensitive imaging of the HER-2 positive tumor since we are unable to detect the imaging signal in the tumors following systemic delivery of non-targeted IONPs into the mice bearing HER-2 positive SKOV3 tumors. Furthermore, imaging signals and the IONPs are not detected in HER-2 low expressing OVCAR3 tumors after systemic delivery of HER-2 targeted-IONPs. Since HER-2 is expressed in a high percentage of ovarian cancers, the HER-2 targeted dual imaging modality IONPs have potential for the development of novel targeted imaging and therapeutic nanoparticles for ovarian cancer detection, targeted drug delivery, and image-guided therapy and surgery.

Targeted therapies often depend on the expression of the target present in the tumor. This expression can be difficult to ascertain in widespread metastases. (18)F-FDG PET/CT, although sensitive, is nonspecific for particular tumor markers. Here, we compare the use of a human epidermal growth factor receptor 2 (HER2)–specific (18)F-Z(HER2:342)-Affibody and (18)F-FDG in HER2-expressing pulmonary metastases in a murine model of breast cancer. METHODS: The lung metastasis model was established by intravenous injection of MDA-MB-231(HER2)-Luc human breast cancer cells into the tail vein. Bioluminescence imaging was used to evaluate metastasis progression. Uptake of (18)F-Z(HER2:342)-Affibody and (18)F-FDG was confirmed by coregistration of the PET images with MR and CT images. At the end of the study, the presence of neoplastic cells and HER2 expression in lung tissues, and distribution of the tracer, were assessed ex vivo by immunohistochemistry and autoradiography. RESULTS: (18)F-Z(HER2:342)-Affibody successfully targeted HER2-positive lesions in the lung and allowed detection of metastases as early as 9 wk after injection of cells. In contrast, (18)F-FDG uptake was often masked by surrounding inflammatory changes and was nonspecific for HER2 expression. HER2 expression at a cellular level correlated well with tracer uptake on autoradiography. CONCLUSION: (18)F-Z(HER2:342)-Affibody is a promising tracer for evaluation of HER2 status of breast cancer metastases and is more specific for detecting HER2-positive lesions than (18)F-FDG.

Nuclear medicine is a multidisciplinary field that develops and uses instrumentation and tracers (radiophar- maceuticals) to study physiological processes and noninva- sively diagnose, stage, and treat diseases. Particularly, it offers a unique means to study cancer biology in vivo and to optimize cancer therapy for individual patients. A tracer is either a radionuclide alone, such as iodine-131 or a radiola- bel in a carrier molecule such as 18 F in fluorodeoxyglucose ( 18 F-FDG), or other feasible radionuclide attached to a drug, a protein, or a peptide, which when introduced into the body, would accumulate in the tissue of interest. Nuclear medicine imaging, including single-photon emission com- puter tomography and positron emission tomography, can provide important quantitative and functional information about normal tissues or disease conditions, in contrast to conventional, anatomical imaging techniques such as ultra- sound, computed tomography, or magnetic resonance imag- ing. For treatment, tumor-targeting agents, conjugated with therapeutic radionuclides, may be used to deposit lethal radiation at tumor sites. This review outlines the role of nuclear medicine in modern cancer therapy.

The major goal in developing drugs targeting specific tumor receptors, such as Monoclonal AntiBodies (MAB), is to make a drug compound that targets selectively the cancer-causing biomarkers, inhibits their functionality, and/or delivers the toxin specifically to the malignant cells. Recent advances in MABs show that their efficacy depends strongly on characterization of tumor biomarkers. Therefore, one of the main tasks in cancer diagnostics and treatment is to develop non-invasive in-vivo imaging techniques for detection of cancer biomarkers and monitoring their down regulation during the treatment. Such methods can potentially result in a new imaging and treatment paradigm for cancer therapy. In this article we have reviewed fluorescence imaging approaches, including those developed in our group, to detect and monitor Human Epidermal Growth Factor 2 (HER2) receptors before and during therapy. Transition of these techniques from the bench to bedside is the ultimate goal of our project. Similar approaches can be used potentially for characterization of other cancer related cell biomarkers.

Introduction: Cancers overexpressing HER2 gene are usually described as more aggressive and are associated with poor prognosis. Although introduction of trastuzumab, a HER2-specific humanized antibody, significantly improved the outcome, there are still number of patients who do not respond or acquire resistance to HER2-targeted therapy. We have previously described the construction, expression, and in vitro characterization of Affitoxin, a recombinant protein combining HER2- specific Affibody and modified Pseudomonas exotoxin A (PE 38) that blocks protein synthesis by ADP ribosylation of eEF-2 (Zielinski et al. 2009). In this report we present in vivo data. Materials and Methods. Recombinant Affitoxins were expressed and purified from the soluble fraction of E.coli. HER2 specificity was confirmed in vitro by measurement of the residual ATP level in N87 cells treated with Affitoxin and “Non-specific” toxin. containing “off-target” instead of HER2 - Affibodies. Acute toxicity and immunogenicity studies were performed in female Balb/c mice. Affitoxin clearance rate was determined by ELISA and residual serum toxicity. Biodistribution in subcutaneous BT474 tumors model was determined by NIR optical imaging. In vivo efficacy of the drug was verified in subcutaneous (BT474, SKOV3) and intraperitoneal (SKOV3-luc-D3) tumor models. Results. In this work we have confirmed that HER2-specific Affitoxin is a potent agent eliminating HER2-overexpressing cells in vitro at low picomolar concentration range, while non-specific toxin-containing offtarget Affitoxin is four orders of magnitude less efficient. Acute toxicity studies showed that Affitoxin is well tolerated by mice with LD50 = 0.572±0.051 mg/kg. Injection of six doses every third day neither lead to significant weigh loss of the animal nor induced severe liver problems. Pharmacokinetic data indicated fast clearance of Affitoxin from the circulation with half-life shorter than 10 min. Using human tumor xenograft models, we have shown that Affitoxin accumulates in HER2- overexpressing BT474 tumors, leading not only to reduction of growth rate but also permanent shrinkage of relatively large ( Immunogenicity studies indicated that Affitoxin is less immunogenic than toxin containing antibody fragments fused to PE38 (HA22). Conclusions. Affitoxin is a novel recombinant protein, using high affinity Affibody molecules to target HER2 receptors. Our in vitro and in vivo data strongly suggest that Affitoxin might be an attractive alternative or complement for existing HER2 targeted therapies Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P3-14-23.

Prostate cancer is a common cancer in men and continues to be a major health problem. Imaging plays an essential role in the clinical management of patients. An important goal for prostate cancer imaging is more accurate disease characterization through the synthesis of anatomic, functional, and molecular imaging information. Developments in imaging technologies, specifically magnetic resonance imaging (MRI) and positron emission tomography (PET)/computed tomography (CT), have improved the detection rate of prostate cancer. MRI has improved lesion detection and local staging. Furthermore, MRI allows functional assessment with techniques such as diffusion-weighted MRI, MR spectroscopy, and dynamic contrast-enhanced MRI. The most common PET radiotracer, (18)F-fluorodeoxyglucose, is not very useful in prostate cancer. However, in recent years other PET tracers have improved the accuracy of PET/CT imaging of prostate cancer. Among these, choline (labeled with (18)F or (11)C), (11)C-acetate, and (18)F-fluoride have demonstrated promising results, and other new radiopharmaceuticals are currently under evaluation in preclinical and clinical studies.

Traditional morphologically based imaging modalities are now being complemented by positron emission tomography (PET)/computed tomography (CT) in prostate cancer. Metastatic prostate cancer is an attractive target for radioimmunotherapy (RIT) as no effective therapies are available. This review highlights the most important achievements within the last year in PET/CT and RIT of prostate cancer.Conflicting results exist on the use of choline for detection of malignant disease in the prostate gland. The role of PET/CT in N-staging remains to be elucidated further. However, F-choline and C-choline PET/CT have been demonstrated to be useful for detection of recurrence. F-choline and F-fluoride PET/CT are useful for detection of bone metastases. Prostate tumor antigens may be used as targets for RIT. Prostate-specific membrane antigen is currently under focus of a number of diagnostic and therapeutic strategies. J591, a monoclonal antibody, which targets the extracellular domain of prostate-specific membrane antigen, shows promising results. HER2 receptors may also have a potential as target for PET/CT imaging and RIT of advanced prostate cancer.PET/CT in prostate cancer has proven to play a significant role, in particular for detection of prostate cancer recurrence and bone metastases. RIT of metastatic prostate cancer warrants further investigations.

To evaluate the efficacy and safety of boron neutron capture therapy (BNCT) for glioblastoma multiforme (GBM) using a novel protocol for the boronophenylalanine-fructose (BPA-F) infusion.This phase II study included 30 patients, 26-69 years old, with a good performance status of which 27 have undergone debulking surgery. BPA-F (900 mg BPA/kg body weight) was given i.v. over 6h. Neutron irradiation started 2h after the completion of the infusion. Follow-up reports were monitored by an independent clinical research institute.The boron-blood concentration during irradiation was 15.2-33.7 microg/g. The average weighted absorbed dose to normal brain was 3.2-6.1 Gy (W). The minimum dose to the tumour volume ranged from 15.4 to 54.3 Gy (W). Seven patients suffered from seizures, 8 from skin/mucous problem, 5 patients were stricken by thromboembolism and 4 from abdominal disturbances in close relation to BNCT. Four patients displayed 9 episodes of grade 3-4 events (WHO). At the time for follow-up, minimum ten months, 23 out of the 29 evaluable patients were dead. The median time from BNCT treatment to tumour progression was 5.8 months and the median survival time after BNCT was 14.2 months. Following progression, 13 patients were given temozolomide, two patients were re-irradiated, and two were re-operated. Patients treated with temozolomide lived considerably longer (17.7 vs. 11.6 months). The quality of life analysis demonstrated a progressive deterioration after BNCT.Although, the efficacy of BNCT in the present protocol seems to be comparable with conventional radiotherapy and the treatment time is shorter, the observed side effects and the requirement of complex infrastructure and higher resources emphasize the need of further phase I and II studies, especially directed to improve the accumulation of (10)B in tumour cells.

Registration is critical for image‐based treatment planning and image‐guided treatment delivery. Although automatic registration is available, manual, visual‐based image fusion using three orthogonal planar views (3P) is always employed clinically to verify and adjust an automatic registration result. However, the 3P fusion can be time consuming, observer dependent, as well as prone to errors, owing to the incomplete 3‐dimensional (3D) volumetric image representations. It is also limited to single‐pixel precision (the screen resolution). The 3D volumetric image registration (3DVIR) technique was developed to overcome these shortcomings. This technique introduces a 4th dimension in the registration criteria beyond the image volume, offering both visual and quantitative correlation of corresponding anatomic landmarks within the two registration images, facilitating a volumetric image alignment, and minimizing potential registration errors. The 3DVIR combines image classification in real‐time to select and visualize a reliable anatomic landmark, rather than using all voxels for alignment. To determine the detection limit of the visual and quantitative 3DVIR criteria, slightly misaligned images were simulated and presented to eight clinical personnel for interpretation. Both of the criteria produce a detection limit of 0.1 mm and 0.1°. To determine the accuracy of the 3DVIR method, three imaging modalities (CT, MR and PET/CT) were used to acquire multiple phantom images with known spatial shifts. Lateral shifts were applied to these phantoms with displacement intervals of 5.0±0.1mm. The accuracy of the 3DVIR technique was determined by comparing the image shifts determined through registration to the physical shifts made experimentally. The registration accuracy, together with precision, was found to be: 0.02±0.09mm for CT/CT images, 0.03±0.07mm for MR/MR images, and 0.03±0.35mm for PET/CT images. This accuracy is consistent with the detection limit, suggesting an absence of detectable systematic error. This 3DVIR technique provides a superior alternative to the 3P fusion method for clinical applications. PACS numbers: 87.57.nj, 87.57.nm, 87.57.‐N, 87.57.‐s

*Departments of Radiation Oncology, Genetics and Genomic Sciences, Dermatology and Preventive Medicine, Icahn School of Medicine at Mount Sinai, New York, New York; yDepartment of Radiation Oncology, New York University School of Medicine, New York, New York; zClinical Radiation Oncology Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland; xDepartment of Radiation Oncology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts; kDepartment of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, New York; {Department of Radiation Oncology, University of Rochester Medical Center, Rochester, New York; Department of Radiation Oncology, GRU Cancer Center and Medical College of Georgia, Georgia Regents University, Augusta, Georgia; **Departments of Pathology and Pediatrics, Albert Einstein College of Medicine, Bronx, New York; yyDepartment of Biomedical Informatics, University of Arkansas for Medical Sciences, Little Rock, Arkansas; zzDepartment of Radiation Oncology, The Johns Hopkins University School of Medicine, Baltimore, Maryland; and xxDepartment of Radiation Oncology, University of Pennsylvania, Philadelphia, Pennsylvania

Cancer treatment evolves through oncology clinical trials. Cancer trials are multimodal and complex. Assuring high-quality data are available to answer not only study objectives but also questions not anticipated at study initiation is the role of quality assurance. The National Cancer Institute reorganized its cancer clinical trials program in 2014. The National Clinical Trials Network (NCTN) was formed and within it was established a Diagnostic Imaging and Radiation Therapy Quality Assurance Organization. This organization is Imaging and Radiation Oncology Core, the Imaging and Radiation Oncology Core Group, consisting of 6 quality assurance centers that provide imaging and radiation therapy quality assurance for the NCTN. Sophisticated imaging is used for cancer diagnosis, treatment, and management as well as for image-driven technologies to plan and execute radiation treatment. Integration of imaging and radiation oncology data acquisition, review, management, and archive strategies are essential for trial compliance and future research. Lessons learned from previous trials are and provide evidence to support diagnostic imaging and radiation therapy data acquisition in NCTN trials.

Purpose: To develop and optimize a technique for inverse treatment planning based solely on magnetic resonance imaging (MRI) during high-dose-rate brachytherapy for prostate cancer. Methods and Materials: Phantom studies were performed to verify the spatial integrity of treatment planning based on MRI. Data were evaluated from 10 patients with clinically localized prostate cancer who had undergone two high-dose-rate prostate brachytherapy boosts under MRI guidance before and after pelvic radiotherapy. Treatment planning MRI scans were systematically evaluated to derive a class solution for inverse planning constraints that would reproducibly result in acceptable target and normal tissue dosimetry. Results: We verified the spatial integrity of MRI for treatment planning. MRI anatomic evaluation revealed no significant displacement of the prostate in the left lateral decubitus position, a mean distance of 14.47 mm from the prostatic apex to the penile bulb, and clear demarcation of the neurovascular bundles on postcontrast imaging. Derivation of a class solution for inverse planning constraints resulted in a mean target volume receiving 100% of the prescribed dose of 95.69%, while maintaining a rectal volume receiving 75% of the prescribed dose of

Boron neutron capture therapy (BNCT) is dependent on the selective accumulation of boron-10 in tumour cells. To maximise the radiation effect, the neutrons should be delivered when the ratio between the boron concentration in tumour cells to that in normal tissues reaches maximum. However, the pharmacokinetics of p-boronophenylalanine (BPA) and other boron delivery agents are only partly known. We used microdialysis to investigate the extracellular in vivo kinetics of boron in three intracerebral compartments -- solid tumour, brain adjacent to tumour (BAT), and the normal brain, as well as the subcutaneous tissue before, during, and after BNCT treatment. The findings were compared to the pharmacokinetics of BPA in the blood. We also measured the glucose metabolism and the levels of glutamate and glycerol in those compartments. Four patients were studied, two patients underwent surgical tumour resection and in two a stereotactic biopsy was performed. The patients were given BPA (900 mg/kg body weight) by a 6-h infusion. The infusion was completed approximately 2-3 h before neutron irradiation. In tumour tissue the extracellular concentration of BPA followed that of blood with a maximal concentration of 31.2 ppm and a maximal ratio vs. blood of 1.07. In BAT, the maximal concentration of BPA was 18.0 ppm with the peak level delayed for 4-6 h compared to the peak in blood with a maximal ratio of 1.2. Maximal blood concentration found was 41.0 ppm. The uptake of BPA in the normal brain was considerably lower than that in the blood and tumour tissue. No change in glucose metabolism was observed. The extracellular level of glycerol was increased after treatment in tumour tissue but not in normal brain suggesting a selective acute cytotoxic effect of BNCT on tumour cells.

A boron neutron capture therapy ( BNCT) facility has been constructed at Studsvik, Sweden. It includes two filter/ moderator configurations. One of the resulting neutron beams has been optimized for clinical irradiations with a filter/ moderator system that allows easy variation of the neutron spectrum from the thermal to the epithermal energy range. The other beam has been designed to produce a large uniform field of thermal neutrons for radiobiological research. Scientific operations of the Studsvik BNCT project are overseen by the Scientific Advisory Board comprised of representatives of major universities in Sweden. Furthermore, special task groups for clinical and preclinical studies have been formed to facilitate collaboration with academia. The clinical Phase II trials for glioblastoma are sponsored by the Swedish National Neuro- Oncology Group and, presently, involve a protocol for BNCT treatment of glioblastoma patients who have not received any therapy other than surgery. In this protocol, p- boronophenylalanine ( BPA), administered as a 6- h intravenous infusion, is used as the boron delivery agent. As of January 2002, 17 patients were treated. The 6- h infusion of 900 mg BPA/ kg body weight was shown to be safe and resulted in the average blood - boron concentration of 24 mu g/ g ( range: 15 - 32 mu g/ g) at the time of irradiation ( approximately 2 - 3 h post- infusion). Peak and average weighted radiation doses to the brain were in the ranges of 8.0 - 15.5 Gy( W) and 3.3 - 6.1 Gy( W), respectively. So far, no severe BNCT- related acute toxicities have been observed. Due to the short follow- up time, it is too early to evaluate the efficacy of these studies. (Less)

Purpose: Advances in tumor biology created a foundation for targeted therapy aimed at inactivation of specific molecular mechanisms responsible for cell malignancy. In this paper, we used in vivo fluorescence lifetime imaging with HER2-targeted fluorescent probes as an alternative imaging method to investigate the efficacy of targeted therapy with 17-DMAG (an HSP90 inhibitor) on tumors with high expression of HER2 receptors. Experimental Design: HER2-specific Affibody, conjugated to Alexafluor 750, was injected into nude mice bearing HER2-positive tumor xenograft. The fluorescence lifetime was measured before treatment and monitored after the probe injections at 12 hours after the last treatment dose, when the response to the 17-DMAG therapy was the most pronounced as well as a week after the last treatment when the tumors grew back almost to their pretreatment size. Results: Imaging results showed significant difference between the fluorescence lifetimes at the tumor and the contralateral site (∼0.13 ns) in the control group (before treatment) and 7 days after the last treatment when the tumors grew back to their pretreatment dimensions. However, at the time frame that the treatment had its maximum effect (12 hours after the last treatment), the difference between the fluorescence lifetime at the tumor and contralateral site decreased to 0.03 ns. Conclusions: The results showed a good correlation between fluorescence lifetime and the efficacy of the treatment. These findings show that in vivo fluorescence lifetime imaging can be used as a promising molecular imaging tool for monitoring the treatment outcome in preclinical models and potentially in patients. Clin Cancer Res; 20(13); 3531–9. ©2014 AACR.

// Katharina Feldinger 1 , Daniele Generali 3 , Gabriela Kramer-Marek 4,8 , Merel Gijsen 1 , Tzi Bun Ng 5 , Jack Ho Wong 5 , Carla Strina 3 , Mariarosa Cappelletti 3 , Daniele Andreis 3 , Ji-Liang Li 2 , Esther Bridges 2 , Helen Turley 2 , Russell Leek 2 , Ioannis Roxanis 6 , Jacek Capala 4 , Gillian Murphy 7 , Adrian L. Harris 2 and Anthony Kong 1 1 Human Epidermal Growth Factor Group, Department of Oncology, Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, UK 2 Growth Factor Group, Department of Oncology, Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, UK 3 U.O. Multidisciplinare di Patologia Mammaria, U.S Terapia Molecolare e Farmacogenomica, A.O. Instituti Ospitalieri di Cremona, Cremona, Italy 4 National Institutes of Health, Radiation Oncology Branch, Bethesda MD, US 5 School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Tai Po Road, Sha Tin, Hong Kong 6 Department of Cellular Pathology, Oxford University Hospitals and Oxford Biomedical Research Centre, Oxford, UK 7 Cancer Research UK Cambridge Institute, Li Ka Shing Centre, Robinson Way, Cambridge, UK 8 Institute of Cancer Research, Division of Radiotherapy and Imaging, Belmont, Sutton, Surrey, UK (New address) Correspondence: Anthony Kong, email: // Keywords : Trastuzumab, resistance, ADAM10, HER2, survival Received : March 8, 2014 Accepted : May 7, 2014 Published : May 8, 2014 Abstract Trastuzumab prolongs survival in HER2 positive breast cancer patients. However, resistance remains a challenge. We have previously shown that ADAM17 plays a key role in maintaining HER2 phosphorylation during trastuzumab treatment. Beside ADAM17, ADAM10 is the other well characterized ADAM protease responsible for HER ligand shedding. Therefore, we studied the role of ADAM10 in relation to trastuzumab treatment and resistance in HER2 positive breast cancer. ADAM10 expression was assessed in HER2 positive breast cancer cell lines and xenograft mice treated with trastuzumab. Trastuzumab treatment increased ADAM10 levels in HER2 positive breast cancer cells (p≤0.001 in BT474; p≤0.01 in SKBR3) and in vivo (p≤0.0001) compared to control, correlating with a decrease in PKB phosphorylation. ADAM10 inhibition or knockdown enhanced trastuzumab response in naive and trastuzumab resistant breast cancer cells. Trastuzumab monotherapy upregulated ADAM10 (p≤0.05); and higher pre-treatment ADAM10 levels correlated with decreased clinical response (p≤0.05) at day 21 in HER2 positive breast cancer patients undergoing a trastuzumab treatment window study. Higher ADAM10 levels correlated with poorer relapse-free survival (p≤0.01) in a cohort of HER2 positive breast cancer patients. Our studies implicate a role of ADAM10 in acquired resistance to trastuzumab and establish ADAM10 as a therapeutic target and a potential biomarker for HER2 positive breast cancer patients.

The role of HER4 in breast cancer is controversial and its role in relation to trastuzumab resistance remains unclear. We showed that trastuzumab treatment and its acquired resistance induced HER4 upregulation, cleavage and nuclear translocation. However, knockdown of HER4 by specific siRNAs increased trastuzumab sensitivity and reversed its resistance in HER2 positive breast cancer cells. Preventing HER4 cleavage by a γ-secretase inhibitor and inhibiting HER4 tyrosine kinase activity by neratinib decreased trastuzumab-induced HER4 nuclear translocation and enhanced trastuzumab response. There was also increased nuclear HER4 staining in the tumours from BT474 xenograft mice and human patients treated with trastuzumab. Furthermore, nuclear HER4 predicted poor clinical response to trastuzumab monotherapy in patients undergoing a window study and was shown to be an independent poor prognostic factor in HER2 positive breast cancer. Our data suggest that HER4 plays a key role in relation to trastuzumab resistance in HER2 positive breast cancer. Therefore, our study provides novel findings that HER4 activation, cleavage and nuclear translocation influence trastuzumab sensitivity and resistance in HER2 positive breast cancer. Nuclear HER4 could be a potential prognostic and predictive biomarker and understanding the role of HER4 may provide strategies to overcome trastuzumab resistance in HER2 positive breast cancer.

We have previously reported a method for labeling epidermal growth factor (EGF) with technetium-99m and have shown that 99mTc-EGF localized in EGF receptor (R) positive intracerebral C6EGFR rat gliomas following intratumoral (i.t.) injection of the radioligand. In the present study, we have evaluated the potential use of 99mTc-EGF as a tumor targeting agent after systemic administration to Fischer rats bearing intracerebral implants of C6EGFR gliomas. Radiolocalization was determined following intravenous (i.v.) or intracarotid (i.c.) injection with or without hyperosmotic mannitol induced disruption of the blood–brain barrier (BBB-D). As determined by γ-scintillation counting, 4 h after i.c. injection of 99mTc-EGF, 0.34% of the injected dose per gram (% ID/g) was localized in C6EGFR tumors, which expressed 105–106 EGFR sites per cell, compared to 0.07% ID/g in animals bearing C6 wildtype gliomas, which do not express EGFR. The corresponding tumor to brain ratios were 5.6 and 1.6, respectively. Tumors could be visualized by external γ-scintigraphy in rats bearing C6EGFR but not C6 wildtype gliomas, thereby establishing that radiolocalization was dependent upon receptor expression. Intracarotid administration of 99mTc-EGF significantly increased tumor uptake compared to i.v. injection (0.34 vs 0.14% ID/g, p 0.1). The uptake of 99mTc-EGF was ∼4–9% ID/g in the liver and 12–20% ID/g in the kidneys after i.c. or i.v. administration. External γ-scintigraphy of regions of interest over the liver and kidneys revealed that ∼70–80% of the whole body radioactivity accumulated in these organs, and only 0.47–0.83% in the tumor following i.v. or i.c. administration of 99mTc-EGF. Our study has demonstrated that EGF can be used as a specific targeting agent for EGFR (+) rat brain tumors. However, it is unlikely that systemic injection of EGF-based bioconjugates can deliver sufficient amounts of the ligand to brain tumors for therapeutic purposes and direct delivery by means of either intratumoral injection or a variant of it such as convection enhanced delivery will be required.

Twelve normal dogs underwent brain irradiation in a mixed-radiation, mainly epithermal neutron field at the Brookhaven Medical Research Reactor following intravenous infusion of 950 mg of 10B-enriched BPA/kg as its fructose complex. The 5 x 10 cm irradiation aperture was centered over the left hemisphere. For a subgroup of dogs reported previously, we now present more detailed analyses including dose-volume relationships, longer follow-ups, MRIs, and histopathological observations. Peak doses (delivered to 1 cm3 of brain at the depth of maximum thermal neutron flux) ranged from 7.6 Gy (photon-equivalent dose: 11.8 Gy-Eq) to 11.6 Gy (17.5 Gy-Eq). The average dose to the brain ranged from 3.0 Gy (4.5 Gy-Eq) to 8.1 Gy (11.9 Gy-Eq) and to the left hemisphere, 6.6 Gy (10.1 Gy-Eq) to 10.0 Gy (15.0 Gy-Eq). Maximum tolerated 'threshold' doses were 6.7 Gy (9.8 Gy-Eq) to the whole brain and 8.2 Gy (12.3 Gy-Eq) to one hemisphere. The threshold peak brain dose was 9.5 Gy (14.3 Gy-Eq). At doses below threshold, some dogs developed subclinical MRI changes. Above threshold, all dogs developed dose-dependent MRI changes, neurological deficits, and focal brain necrosis.