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Simple Summary: Neutron capture therapy, or NCT, is a unique irradiation-based method that is used to treat invasive advanced tumors as it minimizes the impact on healthy cells and tissues. Modern neutron sources for NCT include accelerators that can be installed in treatment facilities. One of the main conditions for the successful application of NCT is sufficient accumulation of the drug in tumor cells which allows it to capture neutrons, be activated, and release energy that destroys cancer cells. Among the elements capable of capturing neutrons, boron, gadolinium, and lithium are considered to be the most suitable for NCT. In our study, we showed the results of neutron capture therapy with gadolinium in a group of dogs and cats with spontaneous tumors to clarify the technical aspects of the method while adjusting the treatment conditions as close as possible to those of clinical trials. We conducted a clinical veterinary study on neutron capture therapy (NCT) at a neutron-producing accelerator with seven incurable pets with spontaneous tumors and gadolinium as a neutron capture agent (gadolinium neutron capture therapy, or GdNCT). Gadolinium-containing dimeglumine gadopentetate, or Gd-DTPA (Magnevist®, 0.6 mL/kg b.w.), was used. We observed mild and reversible toxicity related to the treatment. However, no significant tumor regression in response to the treatment was observed. In most cases, there was continued tumor growth. Overall clinical improvement after treatment was only temporary. The use of Gd-DTPA for NCT had no significant effects on the life expectancy and quality of life of animals with spontaneous tumors. Further experiments using more advanced gadolinium compounds are needed to improve the effect of GdNCT so that it can become an alternative to boron neutron capture therapy. Such studies are also necessary for further NCT implementation in clinical practice as well as in veterinary medicine. [ABSTRACT FROM AUTHOR]

Sufficient boron-10 isotope (10B) accumulation by tumor cells is one of the main requirements for successful boron neutron capture therapy (BNCT). The inability of the clinically registered 10B-containing borophenylalanine (BPA) to maintain a high boron tumor concentration during neutron irradiation after a single injection has been partially solved by its continuous infusion; however, its lack of persistence has driven the development of new compounds that overcome the imperfections of BPA. We propose using elemental boron nanoparticles (eBNPs) synthesized by cascade ultrasonic dispersion and destruction of elemental boron microparticles and stabilized with hydroxyethylcellulose (HEC) as a core component of a novel boron drug for BNCT. These HEC particles are stable in aqueous media and show no apparent influence on U251, U87, and T98G human glioma cell proliferation without neutron beam irradiation. In BNCT experiments, cells incubated with eBNPs or BPA at an equivalent concentration of 40 µg 10B/mL for 24 h or control cells without boron were irradiated at an accelerator-based neutron source with a total fluence of thermal and epithermal neutrons of 2.685, 5.370, or 8.055 × 1012/cm2. The eBNPs significantly reduced colony-forming capacity in all studied cells during BNCT compared to BPA, verified by cell-survival curves fit to the linear-quadratic model and calculated radiobiological parameters, though the effect of both compounds differed depending on the cell line. The results of our study warrant further tumor targeting-oriented modifications of synthesized nanoparticles and subsequent in vivo BNCT experiments. [ABSTRACT FROM AUTHOR]

Simple Summary: Accelerator-based neutron sources for boron neutron capture therapy (BNCT) are potentially more accessible than nuclear reactors but many technical issues in clinical trials and further routine therapy remain to be studied. We aim to broaden the understanding of these issues with a study of BNCT in 10 cats and dogs, highlighting practical issues, using an accelerator-based neutron source. Using larger animals with tumors mimicking human clinical progression is an important intermediate step to clinical BNCT development. (1) Background: accelerator-based neutron sources are a new frontier for BNCT but many technical issues remain. We aimed to study such issues and results in larger-animal BNCT (cats and dogs) with naturally occurring, malignant tumors in different locations as an intermediate step in translating current research into clinical practice. (2) Methods: 10 pet cats and dogs with incurable, malignant tumors that had no treatment alternatives were included in this study. A tandem accelerator with vacuum insulation was used as a neutron source. As a boron-containing agent, 10B-enriched sodium borocaptate (BSH) was used at a dose of 100 mg/kg. Animal condition as well as tumor progression/regression were monitored. (3) Results: regression of tumors in response to treatment, improvements in the overall clinical picture, and an increase in the estimated duration and quality of life were observed. Treatment-related toxicity was mild and reversible. (4) Conclusions: our study contributes to preparations for human BNCT clinical trials and suggests utility for veterinary oncology. [ABSTRACT FROM AUTHOR]

Boron neutron capture therapy (BNCT) is a cancer treatment with clinically demonstrated efficacy using boronophenylalanine (BPA) and sodium mercaptododecaborate (BSH). However, tumor tissue selectivity of BSH and retention of BPA in tumor cells is a constant problem. To ensure boron accumulation and retention in tumor tissues, we designed a novel polyethylene glycol (PEG)-based boron-containing lipid (PBL) and examined the potency of delivery of boron using novel PBL-containing liposomes, facilitated by the enhanced permeability and retention (EPR) effect. PBL was synthesized by the reaction of distearoylphosphoethanolamine and BSH linked by PEG with Michael addition while liposomes modified using PBL were prepared from the mixed lipid at a constant molar ratio. In this manner, novel boron liposomes featuring BSH in the liposomal surfaces, instead of being encapsulated in the inner aqueous phase or incorporated in the lipid bilayer membrane, were prepared. These PBL liposomes also carry additional payload capacity for more boron compounds (or anticancer agents) in their inner aqueous phase. The findings demonstrated that PBL liposomes are promising candidates to effect suitable boron accumulation for BNCT. [ABSTRACT FROM AUTHOR]

Simple Summary: Accelerator-based boron neutron capture therapy (BNCT) has opened up new perspectives in increasing cancer treatment efficacy, including malignant brain tumors and particularly glioblastoma. We studied dosimetry control optimization, neutron beam parameter adjustment, and two boron compound combinations (along with single and double irradiation regimens) to assess safety and increase therapy efficacy, using a U87MG xenotransplant immunodeficient mouse model. In two sets of experiments, we achieved increases in tumor-growth inhibition (to 80–83%), a neutron capture therapy ratio of 2:1 (two times higher neutron capture therapy efficacy than neutron irradiation without boron), and increases in animal life expectancy, from 9 to 107 days, by treatment parameter adjustment. These results will contribute to the development of clinical-trial protocols for accelerator-based BNCT and further innovations in this cancer treatment method. (1) Background: Developments in accelerator-based neutron sources moved boron neutron capture therapy (BNCT) to the next phase, where new neutron radiation parameters had to be studied for the treatment of cancers, including brain tumors. We aimed to further improve accelerator-BNCT efficacy by optimizing dosimetry control, beam parameters, and combinations of boronophenylalanine (BPA) and sodium borocaptate (BSH) administration in U87MG xenograft-bearing immunodeficient mice with two different tumor locations. (2) Methods: The study included two sets of experiments. In Experiment #1, BPA only and single or double irradiation in higher doses were used, while, in Experiment #2, BPA and BSH combinations and single or double irradiation with dosage adjustment were analyzed. Mice without treatment or irradiation after BPA or BPA+BSH injection were used as controls. (3) Results: Irradiation parameter adjustment and BPA and BSH combination led to 80–83% tumor-growth inhibition index scores, irradiation:BNCT ratios of 1:2, and increases in animal life expectancy from 9 to 107 days. (4) Conclusions: Adjustments in dosimetry control, calculation of irradiation doses, and combined use of two 10B compounds allowed for BNCT optimization that will be useful in the development of clinical-trial protocols for accelerator-based BNCT. [ABSTRACT FROM AUTHOR]

Boron neutron capture therapy (BNCT) is an anticancer modality realized through 10B accumulation in tumor cells, neutron irradiation of the tumor, and decay of boron atoms with the release of alpha-particles and lithium nuclei that damage tumor cell DNA. As high-LET particle release takes place inside tumor cells absorbed dose calculations are difficult, since no essential extracellular energy is emitted. We placed gold nanoparticles inside tumor cells saturated with boron to more accurately measure the absorbed dose. T98G cells accumulated ~50 nm gold nanoparticles (AuNPs, 50 µg gold/mL) and boron-phenylalanine (BPA, 10, 20, 40 µg boron-10/mL), and were irradiated with a neutron flux of 3 × 108 cm−2s−1. Gamma-rays (411 keV) emitted by AuNPs in the cells were measured by a spectrometer and the absorbed dose was calculated using the formula D = (k × N × n)/m, where D was the absorbed dose (GyE), k—depth-related irradiation coefficient, N—number of activated gold atoms, n—boron concentration (ppm), and m—the mass of gold (g). Cell survival curves were fit to the linear-quadratic (LQ) model. We found no influence from the presence of the AuNPs on BNCT efficiency. Our approach will lead to further development of combined boron and high-Z element-containing compounds, and to further adaptation of isotope scanning for BNCT dosimetry. [ABSTRACT FROM AUTHOR]