Evaluation of a treatment planning system developed for clinical boron neutron capture therapy and validation against an independent Monte Carlo dose calculation system

Evaluation of calculation accuracy and computation time in a commercial treatment planning system for accelerator-based boron neutron capture therapy

This study aims to evaluate the feasibility of using a commercially available boron neutron capture therapy (BNCT) dose calculation program (NeuCure® Dose Engine) in terms of calculation accuracy and computation time. Treatment planning was simulated under the following calculation parameters: 1.5-5.0 mm grid sizes and 1-10% statistical uncertainties. The calculated monitor units (MUs) and computation times were evaluated. The MUs calculated on grid sizes larger than 2 mm were overestimated by 2% compared with the result of 1.5 mm grid. We established the two-step method for the routine administration of BNCT: multiple calculations involved in beam optimization should be done at a 5 mm grid and a 10% statistical uncertainty (the shortest computation time: 10.3 ± 2.1 min) in the first-step, and final dose calculations should be performed at a 2 mm grid and a 10% statistical uncertainty (satisfied clinical accuracy: 6.9 ± 0.3 h) in the second-step.

Study of accelerator-based epithermal neutron flux depending on Li and Be targets

The Li(p,n) and Be(p,n) reactions are widely used as accelerator-based neutron sources for boron neutron capture therapy (BNCT). Because the energy of the neutrons produced by these reactions is high for BNCT, a moderator is required to reduce the energy to the epithermal energy region. The neutron yields and energy spectra derived from the Li(p,n) and Be(p,n) reactions vary with the incident proton energy; a high proton energy results in a high neutron yield. However, a high proton energy can also increase the neutron energy, and in this case, a high neutron energy requires a thick moderator, which decreases the epithermal neutron flux. Notably, these tradeoffs are not completely clear. Furthermore, the upper limit of the epithermal neutron energy used in different BCNT facilities is not the same. Therefore, epithermal neutron flux estimation with applying an appropriate moderator is necessary for comparing epithernal neutron flux depending on the proton energy, target type, and epithermal neutron range definition. In this study, GEANT4 simulations were performed to determine effective moderator materials and thicknesses. After applying a moderator, we examined the epithermal neutron flux by changing the conditions that can influence the epithermal neutron flux, such as the proton energy, target species (Li and Be), and different definitions of the epithermal neutron region. The results showed that the epithermal neutron flux increases with the increasing proton energy until a certain level for both Li and Be targets. For proton energies above 3 MeV for the Li target and above 7 MeV for the Be target, the epithermal neutron flux decreases or its increase rate gradually decreases. And, when the upper energy limit of the epithermal neutron range is changed from 10 keV to 20 keV or 40 keV, the epithermal neutron flux is more than 109 cm-2 s-1 at a proton energy of 3 MeV for Li target and 8 MeV for Be target.

Preliminary outcomes of boron neutron capture therapy for head and neck cancers as a treatment covered by public health insurance system in Japan: Real-world experiences over a 2-year period

PURPOSE

Since June 2020, boron neutron capture therapy (BNCT) has been a health care service covered by health insurance in Japan to treat locally advanced or recurrent unresectable head and neck cancers. Therefore, we aimed to assess the clinical outcomes of BNCT as a health insurance treatment and explore its role among the standard treatment modalities for head and neck cancers.

MATERIALS AND METHODS

We retrospectively analyzed data from patients who were treated using BNCT at Kansai BNCT Medical Center, Osaka Medical and Pharmaceutical University, between June 2020 and May 2022. We assessed objective response rates based on the Response Evaluation Criteria in Solid Tumors version 1.1, and adverse events based on the Common Terminology Criteria for Adverse Events, version 5.0. Additionally, we conducted a survival analysis and explored the factors that contributed to the treatment results.

RESULTS

Sixty-nine patients (72 treatments) were included in the study, with a median observation period of 15 months. The objective response rate was 80.5%, and the 1-year locoregional control, progression-free survival, and overall survival rates were 57.1% (95% confidence interval [CI]: 43.9%-68.3%), 42.2% (95% CI: 30.1%-53.8%), and 75.4% (95% CI: 62.5%-84.5%), respectively. Locoregional control was significantly longer in patients with earlier TNM staging and no history of chemotherapy.

CONCLUSIONS

BNCT may be an effective treatment option for locally advanced or recurrent unresectable head and neck cancers with no other definitive therapies. If definitive surgery or radiation therapy are not feasible, BNCT should be considered at early disease stages.

Evaluating optimal quality assurance and quality control conditions of activation measurements at the accelerator-based boron neutron capture therapy system employing a lithium target

Evaluating neutron output is important to ensure proper dose delivery for patients in boron neutron capture therapy (BNCT). It requires efficient quality assurance (QA) and quality control (QC) while maintaining measurement accuracy. This study investigated the optimal measurement conditions for QA/QC of activation measurements using a high-purity germanium (HP-Ge) detector in an accelerator-based boron neutron capture therapy (AB-BNCT) system employing a lithium target. The QA/QC uncertainty of the activation measurement was evaluated based on counts, reproducibility, and standard radiation source uncertainties. Measurements in a polymethyl methacrylate (PMMA) cylindrical phantom using aluminum-manganese (Al-Mn) foils and aluminum-gold (Al-Au) foils and measurements in a water phantom using gold wire with and without cadmium cover were performed to determine the optimal measurement conditions. The QA/QC uncertainties of the activation measurements were 4.5% for Au and 4.6% for Mn. The optimum irradiation proton charge and measurement time were determined to be 36 C and 900 s for measurements in a PMMA cylindrical phantom, 7.0 C and 900 s for gold wire measurements in a water phantom, and 54 C and 900 s at 0-2.2 cm depth and 3,600 s at deeper depths for gold wire measurements with cadmium cover. Our results serve as a reference for determining measurement conditions when performing QA/QC of activation measurements using HP-Ge detectors at an AB-BNCT employing a lithium target.

Gamma rays and neutrons attenuation performance of a developed lead borate glass for radiotherapy room

The development of radiation therapy necessitated a continuous R&D for radiotherapy rooms' glass windows to reach the highest levels of protection for the staff of the radiotherapy facility. Therefore, in this article, a novel type of lead borate glass depending on parallel augmenting of lead and boron was produced to be used as gamma-rays and fast and thermal neutrons barriers in radiotherapy rooms. Neutrons and gamma rays' attenuation parameters, fast neutrons removal cross section ${\varSigma}_R$, thermal neutron total cross section ${\sigma}_T$, mass attenuation coefficient $\sigma$, linear attenuation coefficient μ, half-value layer, mean free path, effective atomic number Zeff, effective electron density Neff, and buildup factor for energy absorption (energy absorption buildup factor) and exposure (exposure buildup factor) were studied extensively. Three tools, Phy-X/PSD, EpiXS and XCOM computer programs and the standard mixture rules were utilized to estimate the attenuation parameters. The improvement caused by the augmentation of lead and boron in both gamma rays and neutrons attenuation was evident from the obtained results. The glass containing the highest lead and boron concentration PbB5, 40Pb-50B, which is the most efficient attenuator for gamma rays and both thermal and fast neutrons was recommended to be a distinguished choice as a shield in a radiotherapy room.

Out-of-field dosimetry using a validated PHITS model and computational phantom in clinical BNCT

BACKGROUND

The out-of-field radiation dose for boron neutron capture therapy (BNCT), which results from both neutrons and γ-rays, has not been extensively evaluated. To safely perform BNCT, the neutron and γ-ray distributions inside the treatment room and the whole-body dose should be evaluated during commissioning. Although, certain previous studies have evaluated the whole-body dose in the clinical research phase, no institution providing BNCT covered by health insurance has yet validated the neutron distribution inside the room and the whole-body dose.

PURPOSE

To validate the Monte Carlo model of the BNCT irradiation room extended for the whole-body region and evaluate organ-at-risk (OAR) doses using the validated model with a human-body phantom.

METHODS

First, thermal neutron distribution inside the entire treatment room was measured by placing Au samples on the walls of the treatment room. Second, neutron and gamma-ray dose-rate distributions inside a human-body water phantom were measured. Both lying and sitting positions were considered. Bare Au, Au covered by Cd (Au+Cd), In, Al, and thermoluminescent dosimeters were arranged at 11 points corresponding to locations of the OARs inside the phantom. After the irradiation, γ-ray peaks emitted from the samples were measured by a high-purity germanium detector. The measured counts were converted to the reaction rate per unit charge of the sample. These measurements were compared with results of simulations performed with the Particle and Heavy Ion Transport code System (PHITS). A male adult mesh-type reference computational phantom was used to evaluate OAR doses in the whole-body region. The relative biological effectiveness (RBE)-weighted doses and dose-volume histograms (DVHs) for each OAR were evaluated. The median dose (D50% ) and near-maximum dose (D2% ) were evaluated for 14 OARs in a 1-h-irradiation process. The evaluated RBE-weighted doses were converted to equivalent doses in 2 Gy fractions.

RESULTS

Experimental results within 60 cm from the irradiation center agreed with simulation results within the error bars except at ±20, 30 cm, and those over 70 cm corresponded within one digit. The experimental results of reaction rates or γ-ray dose rate for lying and sitting positions agreed well with the simulation results within the error bars at 8, 4, 11, 7 and 7, 4, 7, 6, 5, 6 out of 11 points, respectively, for Au, Au+Cd, In, Al, and TLD. Among the detectors, the discrepancies in reaction rates between experiment and simulation were most common for Au+Cd, but were observed randomly for measurement points (brain, lung, etc.). The experimental results of γ-ray dose rates were systematically lower than simulation results at abdomen and waist regions for both positions. Extending the PHITS model to the whole-body region resulted in higher doses for all OARs, especially 0.13 Gy-eq increase for D50% of the left salivary gland.

CONCLUSION

The PHITS model for clinical BNCT for the whole-body region was validated, and the OAR doses were then evaluated. Clinicians and medical physicists should know that the out-of-field radiation increases the OAR dose in the whole-body region.

Cancer management from a chronic gastrointestinal function perspective

Bowel dysfunction in cancer is a significant and challenging issue for both clinicians and patients. As cancer survival improves, the impact of gastrointestinal symptoms on quality of life is of ever-increasing relevance. This review aims to provide an overview of the common gastrointestinal complaints seen in cancer sufferers and discuss the principles of management and up to date treatment options available.

Proof-of-concept study on a water phantom-based neutron spectrometer: Experimental test with 252Cf and 241Am-Be sources

Boron neutron capture therapy (BNCT) is a promising cancer treatment that uses energetic ions released from 10B(n, α)7Li reactions. Accurate assessment of neutron energy spectra is important for simulation-based evaluation of neutron doses during BNCT. In this study, a proof-of-concept study was conducted for a neutron spectrometry technique that involves the use of a water phantom, which is commonly used for quality assurance in BNCT, as a moderator. The technique involves applying unfolding to the count rate distribution of the thermal neutron counter measured within the phantom to derive the energy spectrum. We performed experiments using a spherical 3He proportional counter in neutron fields generated by 252Cf and 241Am-Be sources. The results demonstrated that the spectrometer reasonably reproduced neutron spectra and showed the potential of using a water phantom as a moderator for such a technique.

Experimentally determined relative biological effectiveness of cyclotron-based epithermal neutrons designed for clinical BNCT: in vitro study

A neutron beam for boron neutron capture therapy (BNCT) of deep-seated tumours is designed to maintain a high flux of epithermal neutrons, while keeping the thermal and fast neutron component as low as possible. These neutrons (thermal and fast) have a high relative biological effectiveness in comparison with high energy photon beams used for conventional X-ray radiotherapy. In the past, neutrons for the purpose of BNCT were generated using nuclear reactors. However, there are various challenges that arise when installing a reactor in a hospital environment. From 2006, the Kyoto University Research Reactor Institute, in collaboration with Sumitomo Heavy Industries, began the development of an accelerator-based neutron source for clinical BNCT in a bid to overcome the shortcomings of a nuclear reactor-based neutron source. Following installation and beam performance testing, in vitro studies were performed to assess the biological effect of the neutron beam. Four different cell lines were prepared and irradiated using the accelerator-based neutron source. Following neutron and gamma ray irradiation, the survival curve for each cell line was calculated. The biological end point to determine the relative biological effectiveness (RBE) was set to 10% cell survival, and the D10 for each cell line was determined. The RBE of the accelerator-based neutron beam was evaluated to be 2.62.

Correcting for the heterogeneous boron distribution in a tumor for BNCT dose calculation

Most treatment planning systems of boron neutron capture therapy perform dose calculations based on the assumption of a homogeneous boron distribution in tumors, which leads to dose distortion due to the difference between the tumor-to-normal tissue ratio (TNR) range measured in positron emission tomography images (PET) and the target delineation in computed tomography images of the treatment plan. The heterogeneous boron distribution in the target of the treatment plan can be obtained by image fusion. This study provides a way to quantify a heterogeneous boron distribution based on PET images. Theoretically, the same mean TNR for dose calculation by homogeneous or heterogeneous boron distribution should get almost the same mean dose. However, slightly different mean doses are found due to the partial volume effect for a small target volume. The wider the boron distribution is, the higher the impact on the dose-volume histogram distribution is. Dose distribution with homogeneous boron distribution may be overestimated in low boron uptake regions by wrong boron concentration and neutron flux depression. To accurately give the tumor prescription dose and achieve better tumor control, for low dose regions of the tumor should be considered more boron neutron capture therapy treatments or combined with other treatment modalities. The heterogeneous boron distribution must be taken into consideration to have an accurate dose estimation. Therefore, the way how medical physicists and clinicians process the TNR in gross tumor volume should be refined, and the method demonstrated in the work provides a good reference.

Dendritic Structures Functionalized with Boron Clusters, in Particular Carboranes, and Their Biological Properties

The presence of a large number of boron atoms in boron clusters make them attractive tools for the treatment of cancer using boron neutron capture therapy (BNCT). Since the quantity of boron atoms present in the target cell directly affects the effectiveness of BNCT, the idea of gathering a high number of boron atoms in a single entity has emerged many years ago. In this perspective, using hyper-branched macromolecules such as dendrimers appears as an interesting solution. In this review, we will first present the synthesis of diverse dendritic entities (dendrimers, dendrons, and Janus dendrimers) that incorporate boron clusters, in particular carboranes, anywhere in their structure. Four parts of this review present the synthesis of dendrimers having boron clusters on the surface, or inside their structure, of dendrons and of Janus dendrimers, bearing boron clusters. Practically all these boronated dendritic structures were synthesized with the objective to study their biological properties, but in fact only a few of them have been tested against cancerous cells, and even a smaller number was tested in BNCT experiments. The biological experiments are discussed in the fifth part of this review. A good efficiency is generally observed with the boronated dendrimers, even in animal models, with an increase in their mean survival time (MST).

Characterization and clinical utility of different collimator shapes in accelerator-based BNCT systems for head and neck cancer

NeuCure® is the only accelerator-based boron neutron capture therapy (BNCT) system in the world with pharmaceutical approval. Until now, only flat collimators (FCs) on the patient side have been installed. However, in some cases of head and neck cancer patients, positioning the patient close enough to the collimator when using FCs was difficult. Thus, there are concerns about the prolongation of the irradiation time and overdose to normal tissues. To address these issues, a collimator with a convex-extended section on the patient side (extended collimators [ECs]) was developed, and its pharmaceutical approval was obtained in February 2022. This study evaluated the physical characterization and usefulness of each collimator using a simple geometry water phantom model and human model. In the water phantom model, the thermal neutron fluxes at 2 cm depth on the central axis were 5.13 × 108, 6.79 × 108, 1.02 × 109, and 1.17 × 109n/cm2/s for FC(120), FC(150), EC50(120), and EC100(120), respectively, when the distance from the irradiation aperture was kept constant at 18 cm. With ECs, the relative off-axis thermal neutron flux decreased steeply. In the hypopharyngeal cancer human model, the tumor dose changes were within <2%, but the maximum oral mucosa doses were 7.79, 8.51, 6.76, and 4.57 Gy-Eq, respectively. The irradiation times were 54.3, 41.3, 29.2, and 24.8 min, respectively. In cases where positioning the patient close to the collimator is difficult, the use of ECs may reduce the dose to normal tissues and shorten the irradiation time.

Introduction to the Monte Carlo dose engine COMPASS for BNCT

The Monte Carlo method is the most commonly used dose calculation method in the field of boron neutron capture therapy (BNCT). General-purpose Monte Carlo (MC) code (e.g., MCNP) has been used in most treatment planning systems (TPS) to calculate dose distribution, which takes overmuch time in radiotherapy planning. Based on this, we developed COMPASS (COMpact PArticle Simulation System), an MC engine specifically for BNCT dose calculation. Several optimization algorithms are used in COMPASS to make it faster than general-purpose MC code. The parallel computation of COMPASS is performed by the message passing interface (MPI) library and OpenMP commands, which allows the user to increase computational speed by increasing the computer configurations. The physical dose of each voxel is calculated for developing a treatment plan. Comparison results show that the computed dose distribution of COMPASS is in good agreement with MCNP, and the computational efficiency is better than MCNP. These results validate that COMPASS has better performance than MCNP in BNCT dose calculation.

Initial evaluation of accelerator-based neutron source system at the Shonan Kamakura General Hospital

An accelerator-based boron neutron capture therapy (AB-BNCT) system was installed at the Shonan Kamakura General Hospital (SKGH). We confirmed that a stable operation was possible for 1 h at a current of 30 mA. The evaluated thermal neutron flux was 2.8 × 10⁹ cm^-2 s^-1 and in good agreement (±5%) with the calculated values. The daily variation was within ±2%. The ambient dose rate due to residual radioactivity after irradiation was approximately 5 μSv/h using a lead shutter.

Development of optimization method for uniform dose distribution on superficial tumor in an accelerator-based boron neutron capture therapy system

To treat superficial tumors using accelerator-based boron neutron capture therapy (ABBNCT), a technique was investigated, based on which, a single-neutron modulator was placed inside a collimator and was irradiated with thermal neutrons. In large tumors, the dose was reduced at their edges. The objective was to generate a uniform and therapeutic intensity dose distribution. In this study, we developed a method for optimizing the shape of the intensity modulator and irradiation time ratio to generate a uniform dose distribution to treat superficial tumors of various shapes. A computational tool was developed, which performed Monte Carlo simulations using 424 different source combinations. We determined the shape of the intensity modulator with the highest minimum tumor dose. The homogeneity index (HI), which evaluates uniformity, was also derived. To evaluate the efficacy of this method, the dose distribution of a tumor with a diameter of 100 mm and thickness of 10 mm was evaluated. Furthermore, irradiation experiments were conducted using an ABBNCT system. The thermal neutron flux distribution outcomes that have considerable impacts on the tumor's dose confirmed a good agreement between experiments and calculations. Moreover, the minimum tumor dose and HI improved by 20 and 36%, respectively, compared with the irradiation case wherein a single-neutron modulator was used. The proposed method improves the minimum tumor volume and uniformity. The results demonstrate the method's efficacy in ABBNCT for the treatment of superficial tumors.

Development of the Follow-Up Human 3D Oral Cancer Model in Cancer Treatment

As function preservation cancer therapy, targeted radiation therapies have been developed for the quality of life of cancer patients. However, preclinical animal studies evaluating the safety and efficacy of targeted radiation therapy is challenging from the viewpoints of animal welfare and animal protection, as well as the management of animal in radiation-controlled areas under the regulations. We fabricated the human 3D oral cancer model that considers the time axis of the follow up in cancer treatment. Therefore, in this study, the 3D model with human oral cancer cells and normal oral fibroblasts was treated based on clinical protocol. After cancer treatment, the histological findings of the 3D oral cancer model indicated the clinical correlation between tumor response and surrounding normal tissue. This 3D model has potential as a tool for preclinical studies alternative to animal studies.

Accelerator based epithermal neutron source for clinical boron neutron capture therapy

The world’s first accelerator based epithermal neutron source for clinical boron neutron capture therapy (BNCT) was designed, developed, and commissioned between 2008 and 2010 by Sumitomo Heavy Industries in collaboration with Kyoto University at the Kyoto University Institute for Integrated Radiation and Nuclear Science. The accelerator system is cyclotron-based and accelerates a proton up to an energy of approximately 30 MeV. The proton strikes a beryllium target, which produces fast neutrons that traverse a beam shaping assembly composed of a combination of lead, iron, aluminum, and calcium fluoride to reduce the neutron energy down to the epithermal range (∼10 keV) suitable for BNCT. The system is designed to produce an epithermal neutron flux of up to 1.4 × 10 9 n · cm − 2 · s − 1 (exiting from the moderator of a 12 cm diameter collimator) with a proton current of 1 mA. In 2017, the same type of accelerator was installed at the Kansai BNCT Medical Center and in March 2020 the system received medical device approval in Japan (Sumitomo Heavy Industries, NeuCure® BNCT system). Soon after, BNCT for unresectable, locally advanced, and recurrent carcinoma of the head and neck region was approved by the Japanese government for reimbursement covered by the national health insurance system.

Improvement in the neutron beam collimation for application in boron neutron capture therapy of the head and neck region

In June 2020, the Japanese government approved boron neutron capture therapy for the treatment of head and neck cancer. The treatment is usually performed in a single fraction, with the neutron irradiation time being approximately 30–60 min. As neutrons scatter in air and loses its intensity, it is preferable to bring the patient as close to the beam port as possible to shorten the irradiation time. However, this can be a challenge, especially for patients with head and neck cancer, as the shoulders are an obstacle to a clean positioning. In this study, a novel neutron collimation system for an accelerator based neutron source was designed to allow for a more comfortable treatment, without compromising the irradiation time. Experimental measurements confirmed the simulation results and showed the new collimator can reduce the irradiation time by approximately 60% (under the same condition where the distance between the source and the patient surface was kept the same). The dose delivered to the surrounding healthy tissue was reduced with the new collimator, showing a 25% decrease in the D₅₀ of the mucosal membrane. Overall, the use of the newly designed collimator will allow for a more comfortable treatment of the head and neck region, reduce the treatment time, and reduce the dose delivered to the surrounding healthy tissue.

Comprehensive evaluation of dosimetric impact against position errors in accelerator-based BNCT under different treatment parameter settings

Background

Patients who undergo accelerator‐based (AB) boron neutron capture therapy (BNCT) for head and neck cancer in the sitting position are generally uncomfortably immobilized, and patient motion during this treatment may be greater than that in other radiotherapy techniques. Furthermore, the treatment time of BNCT is relatively long (up to approximately 1 h), which increases the possibility of patient movement during treatment. As most BNCT irradiations are performed in a single fraction, the dosimetric error due to patient motion is of greater consequence and needs to be evaluated and accounted for. Several treatment parameters are required for BNCT dose calculation.

Purpose

To investigate the dosimetric impacts (DIs) against position errors using a simple cylindrical phantom for an AB‐BNCT system under different treatment parameter settings.

Methods

The treatment plans were created in RayStation and the dose calculation was performed using the NeuCure® dose engine. A cylindrical phantom (16 cm diameter × 20 cm height) made of soft tissue was modeled. Dummy tumors in the form of a 3‐cm‐diameter sphere were arranged at depths of 2.5 and 6.5 cm (denoted by T_2.5 and T_6.5, respectively). Reference plans were created by setting the following parameters: collimator size = 10, 12, or 15 cm in diameter, collimator‐to‐surface distance (CSD) = 4.0 or 8.0 cm, tumor‐to‐blood ratio (T/B ratio) using ¹⁸F‐fluoro‐borono‐phenylalanine = 2.5 or 5.0, and ¹⁰B concentration in blood = 20, 25, or 30 ppm. The prescribed dose was D_95% ≥ 20 Gy‐eq for both T_2.5 and T_6.5. Based on the reference plans, phantom‐shifted plans were created in 26 directions [all combinations of left–right (LR), anterior–posterior (AP), and superior–inferior (SI) directions) and three distances (1.0, 2.0, and 3.0 cm). The DIs were evaluated at D_80% of the tumors. The shift direction dependency of the DI in the LR, AP, and SI directions was evaluated by conducting a multiple regression analysis (MRA) and other analyses where required.

Results

The coefficients of the MRA of the DIs for LR, AP, and SI shifts were −0.08, 2.16, and −0.04 (p‐values = 0.084, <0.01, and 0.334) for T_2.5 and −0.05, 2.08, and 0.15 (p‐values = 0.526, <0.01, and 0.065) for T_6.5, respectively. The analysis of variance showed that DIs due to the AP shift were significantly greater for smaller collimator sizes on T_2.5 and smaller CSD on T_6.5. Dose reduction due to SI or LR (lateral) shifts was significantly greater for smaller collimator sizes on both T_2.5 and T_6.5 and smaller CSD on T_2.5, according to the Student's t‐test. There were no significant differences in the DIs against both the AP shift and the lateral shift between the different T/B ratios and ¹⁰B concentrations.

Conclusion

The DIs were largely affected by the shift in the AP direction and were influenced by the different treatment parameters.

Clinical Viability of Boron Neutron Capture Therapy for Personalized Radiation Treatment

Simple Summary

Usually, for dose planning in radiotherapy, the tumor is delimited as a volume on the image of the patient together with other clinical considerations based on populational evidence. However, the same prescription dose can provide different results, depending on the patient. Unfortunately, the biological aspects of the tumor are hardly considered in dose planning. Boron Neutron Capture Radiotherapy enables targeted treatment by incorporating boron-10 at the cellular level and irradiating with neutrons of a certain energy so that they produce nuclear reactions locally and almost exclusively damage the tumor cell. This technique is not new, but modern neutron generators and more efficient boron carriers have reactivated the clinical interest of this technique in the pursuit of more precise treatments. In this work, we review the latest technological facilities and future possibilities for the clinical implementation of BNCT and for turning it into a personalized therapy.

Abstract

Boron Neutron Capture Therapy (BNCT) is a promising binary disease-targeted therapy, as neutrons preferentially kill cells labeled with boron (¹⁰B), which makes it a precision medicine treatment modality that provides a therapeutic effect exclusively on patient-specific tumor spread. Contrary to what is usual in radiotherapy, BNCT proposes cell-tailored treatment planning rather than to the tumor mass. The success of BNCT depends mainly on the sufficient spatial biodistribution of ¹⁰B located around or within neoplastic cells to produce a high-dose gradient between the tumor and healthy tissue. However, it is not yet possible to precisely determine the concentration of ¹⁰B in a specific tissue in real-time using non-invasive methods. Critical issues remain to be resolved if BNCT is to become a valuable, minimally invasive, and efficient treatment. In addition, functional imaging technologies, such as PET, can be applied to determine biological information that can be used for the combined-modality radiotherapy protocol for each specific patient. Regardless, not only imaging methods but also proteomics and gene expression methods will facilitate BNCT becoming a modality of personalized medicine. This work provides an overview of the fundamental principles, recent advances, and future directions of BNCT as cell-targeted cancer therapy for personalized radiation treatment.