Optimization of the classical oral cancerization protocol in hamster to study oral cancer therapy.

OBJECTIVE(S): The hamster carcinogenesis model recapitulates oral oncogenesis. Dimethylbenz[a]anthracene (DMBA) cancerization induces early severe mucositis, affecting animal's welfare and causing tissue loss and pouch shortening. "Short" pouches cannot be everted for local irradiation for boron neutron capture therapy (BNCT). Our aim was to optimize the DMBA classical cancerization protocol to avoid severe mucositis, without affecting tumor development. We evaluated BNCT in animals cancerized with this novel protocol. MATERIALS AND METHODS: We studied: Classical cancerization protocol (24 applications) and Classical with two interruptions (completed at the end of the cancerization protocol). BNCT mediated by boronophenylalanine (BPA) was performed in both groups. RESULTS: The twice-interrupted group exhibited a significantly lower percentage of animals with severe mucositis versus the non-interrupted group (17% versus 71%) and a significantly higher incidence of long pouches (100% versus 53%). Tumor development and the histologic characteristics of tumor and precancerous tissue were not affected by the interruptions. For both groups, overall tumor response was more than 80%, with a similar incidence of BNCT-induced severe mucositis. CONCLUSION(S): The twice-interrupted protocol reduced severe mucositis during cancerization without affecting tumor development. This favored the animal's welfare and reduced the number of animals to be cancerized for our studies, without affecting BNCT response.

Electroporation optimizes the uptake of boron-10 by tumor for boron neutron capture therapy (BNCT) mediated by GB-10: a boron biodistribution study in the hamster cheek pouch oral cancer model.

Boron neutron capture therapy (BNCT) is a promising cancer binary therapy modality that utilizes the nuclear capture reaction of thermal neutrons by boron-10 resulting in a localized release of high- and low-linear energy transfer (LET) radiation. Electrochemotherapy (ECT) is based on electroporation (EP) that induces opening of pores in cell membranes, allowing the entry of compounds. Because EP is applied locally to a tumor, the compound is incorporated preferentially by tumor cells. Based on the knowledge that the therapeutic success of BNCT depends centrally on the boron content in tumor and normal tissues and that EP has proven to be an excellent facilitator of tumor biodistribution of an anti-tumor agent, the aim of this study was to evaluate if EP can optimize the delivery of boronated compounds. We performed biodistribution studies and qualitative microdistribution analyses of boron employing the boron compound sodium decahydrodecaborate (GB-10) + EP in the hamster cheek pouch oral cancer model. Syrian hamsters with chemically induced exophytic squamous cell carcinomas were used. A typical EP treatment was applied to each tumor, varying the moment of application with respect to the administration of GB-10 (early or late). The results of this study showed a significant increase in the absolute and relative tumor boron concentration and optimization of the qualitative microdistribution of boron by the use of early EP + GB-10 versus GB-10 without EP. This strategy could be a tool to improve the therapeutic efficacy of BNCT/GB-10 in vivo.

Boron neutron capture therapy (BNCT) translational studies in the hamster cheek pouch model of oral cancer at the new "B2" configuration of the RA-6 nuclear reactor.

Boron neutron capture therapy (BNCT) is based on selective accumulation of B-10 carriers in tumor followed by neutron irradiation. We demonstrated, in 2001, the therapeutic effect of BNCT mediated by BPA (boronophenylalanine) in the hamster cheek pouch model of oral cancer, at the RA-6 nuclear reactor. Between 2007 and 2011, the RA-6 was upgraded, leading to an improvement in the performance of the BNCT beam (B2 configuration). Our aim was to evaluate BPA-BNCT radiotoxicity and tumor control in the hamster cheek pouch model of oral cancer at the new "B2" configuration. We also evaluated, for the first time in the oral cancer model, the radioprotective effect of histamine against mucositis in precancerous tissue as the dose-limiting tissue. Cancerized pouches were exposed to: BPA-BNCT; BPA-BNCT + histamine; BO: Beam only; BO + histamine; CONTROL: cancerized, no-treatment. BNCT induced severe mucositis, with an incidence that was slightly higher than in "B1" experiments (86 vs 67%, respectively). BO induced low/moderate mucositis. Histamine slightly reduced the incidence of severe mucositis induced by BPA-BNCT (75 vs 86%) and prevented mucositis altogether in BO animals. Tumor overall response was significantly higher in BNCT (94-96%) than in control (16%) and BO groups (9-38%), and did not differ significantly from the "B1" results (91%). Histamine did not compromise BNCT therapeutic efficacy. BNCT radiotoxicity and therapeutic effect at the B1 and B2 configurations of RA-6 were consistent. Histamine slightly reduced mucositis in precancerous tissue even in this overly aggressive oral cancer model, without compromising tumor control.

The hamster cheek pouch model for field cancerization studies.

External carcinogens, such as tobacco and alcohol, induce molecular changes in large areas of oral mucosa, which increase the risk of malignant transformation. This condition, known as 'field cancerization', can be detected in biopsy specimens using histochemical techniques, even before histological alterations are identified. The efficacy of these histochemical techniques as biomarkers of early cancerization must be demonstrated in appropriate models. The hamster cheek pouch oral cancer model, universally employed in biological studies and in studies for the prevention and treatment of oral cancer, is also an excellent model of field cancerization. The carcinogen is applied in solution to the surface of the mucosa and induces alterations that recapitulate the stages of cancerization in human oral mucosa. We have demonstrated that the following can be used for the early detection of cancerized tissue: silver staining of nucleolar organizer regions; the Feulgen reaction to stain DNA followed by ploidy analysis; immunohistochemical analysis of fibroblast growth factor-2, immunohistochemical labeling of proliferating cells to demonstrate an increase of epithelial cell proliferation in the absence of inflammation; and changes in markers of angiogenesis (i.e. those indicating vascular endothelial growth factor activity, endothelial cell proliferation and vascular density). The hamster cheek pouch model of oral cancer was also proposed and validated by our group for boron neutron capture therapy studies for the treatment of oral cancer. Clinical trials of this novel treatment modality have been performed and are underway for certain tumor types and localizations. Having demonstrated the efficacy of boron neutron capture therapy to control tumors in the hamster cheek pouch oral cancer model, we adapted the model for the long-term study of field cancerized tissue. We demonstrated the inhibitory effect of boron neutron capture therapy on tumor development in field cancerized tissue with acceptable levels of mucositis, a dose-limiting side-effect.

Assessing advantages of sequential boron neutron capture therapy (BNCT) in an oral cancer model with normalized blood vessels.

BACKGROUND: We previously demonstrated the therapeutic success of sequential boron neutron capture therapy (Seq-BNCT) in the hamster cheek pouch oral cancer model. It consists of BPA-BNCT followed by GB-10-BNCT 24 or 48 hours later. Additionally, we proved that tumor blood vessel normalization with thalidomide prior to BPA-BNCT improves tumor control. The aim of the present study was to evaluate the therapeutic efficacy and explore potential boron microdistribution changes in Seq-BNCT preceded by tumor blood vessel normalization. MATERIAL AND METHODS: Tumor bearing animals were treated with thalidomide for tumor blood vessel normalization, followed by Seq-BNCT (Th+ Seq-BNCT) or Seq-Beam Only (Th+ Seq-BO) in the window of normalization. Boron microdistribution was assessed by neutron autoradiography. RESULTS: Th+ Seq-BNCT induced overall tumor response of 100%, with 87 (4)% complete tumor response. No cases of severe mucositis in dose-limiting precancerous tissue were observed. Differences in boron homogeneity between tumors pre-treated and not pre-treated with thalidomide were observed. CONCLUSION: Th+ Seq-BNCT achieved, for the first time, response in all treated tumors. Increased homogeneity in tumor boron microdistribution is associated to an improvement in tumor control.

Boron neutron capture therapy (BNCT) for liver metastasis in an experimental model: dose­response at five-week follow-up based on retrospective dose assessment in individual rats.

Boron neutron capture therapy (BNCT) was proposed for untreatable colorectal liver metastases. Employing an experimental model of liver metastases in rats, we recently demonstrated that BNCT mediated by boronophenylalanine (BPA-BNCT) at 13 Gy prescribed to tumor is therapeutically useful at 3-week follow-up. The aim of the present study was to evaluate dose­response at 5-week follow-up, based on retrospective dose assessment in individual rats. BDIX rats were inoculated with syngeneic colon cancer cells DHD/K12/TRb. Tumor-bearing animals were divided into three groups: BPA-BNCT (n = 19), Beam only (n = 8) and Sham (n = 7) (matched manipulation, no treatment). For each rat, neutron flux was measured in situ and boron content was measured in a pre-irradiation blood sample for retrospective individual dose assessment. For statistical analysis (ANOVA), individual data for the BPA-BNCT group were pooled according to absorbed tumor dose, BPA-BNCT I: 4.5­8.9 Gy and BPA-BNCT II: 9.2­16 Gy. At 5 weeks post-irradiation, the tumor surface area post-treatment/pre-treatment ratio was 12.2 ± 6.6 for Sham, 7.8 ± 4.1 for Beam only, 4.4 ± 5.6 for BPA-BNCT I and 0.45 ± 0.20 for BPA-BNCT II; tumor nodule weight was 750 ± 480 mg for Sham, 960 ± 620 mg for Beam only, 380 ± 720 mg for BPA-BNCT I and 7.3 ± 5.9 mg for BPA-BNCT II. The BPA-BNCT II group exhibited statistically significant tumor control with no contributory liver toxicity. Potential threshold doses for tumor response and significant tumor control were established at 6.1 and 9.2 Gy, respectively.

Biodistribution of sodium borocaptate (BSH) for boron neutron capture therapy (BNCT) in an oral cancer model.

Boron neutron capture therapy (BNCT) is based on selective accumulation of ¹°B carriers in tumor followed by neutron irradiation. We previously proved the therapeutic success of BNCT mediated by the boron compounds boronophenylalanine and sodium decahydrodecaborate (GB-10) in the hamster cheek pouch oral cancer model. Based on the clinical relevance of the boron carrier sodium borocaptate (BSH) and the knowledge that the most effective way to optimize BNCT is to improve tumor boron targeting, the specific aim of this study was to perform biodistribution studies of BSH in the hamster cheek pouch oral cancer model and evaluate the feasibility of BNCT mediated by BSH at nuclear reactor RA-3. The general aim of these studies is to contribute to the knowledge of BNCT radiobiology and optimize BNCT for head and neck cancer. Sodium borocaptate (50 mg ¹°B/kg) was administered to tumor-bearing hamsters. Groups of 3-5 animals were killed humanely at nine time-points, 3-12 h post-administration. Samples of blood, tumor, precancerous pouch tissue, normal pouch tissue and other clinically relevant normal tissues were processed for boron measurement by optic emission spectroscopy. Tumor boron concentration peaked to therapeutically useful boron concentration values of 24-35 ppm. The boron concentration ratio tumor/normal pouch tissue ranged from 1.1 to 1.8. Pharmacokinetic curves showed that the optimum interval between BSH administration and neutron irradiation was 7-11 h. It is concluded that BNCT mediated by BSH at nuclear reactor RA-3 would be feasible.

Boron neutron capture therapy (BNCT) for liver metastasis: therapeutic efficacy in an experimental model.

Boron neutron capture therapy (BNCT) was proposed for untreatable colorectal liver metastases. The present study evaluates tumor control and potential radiotoxicity of BNCT in an experimental model of liver metastasis. BDIX rats were inoculated with syngeneic colon cancer cells DHD/K12/TRb. Tumor-bearing animals were divided into three groups: BPA-BNCT, boronophenylalanine (BPA) + neutron irradiation; Beam only, neutron irradiation; Sham, matched manipulation. The total absorbed dose administered with BPA-BNCT was 13 ± 3 Gy in tumor and 9 ± 2 Gy in healthy liver. Three weeks post-treatment, the tumor surface area post-treatment/pre-treatment ratio was 0.46 ± 0.20 for BPA-BNCT, 2.7 ± 1.8 for Beam only and 4.5 ± 3.1 for Sham. The pre-treatment tumor nodule mass of 48 ± 19 mg fell significantly to 19 ± 16 mg for BPA-BNCT, but rose significantly to 140 ± 106 mg for Beam only and to 346 ± 302 mg for Sham. For both end points, the differences between the BPA-BNCT group and each of the other groups were statistically significant (ANOVA). No clinical, macroscopic or histological normal liver radiotoxicity was observed. It is concluded that BPA-BNCT induced a significant remission of experimental colorectal tumor nodules in liver with no contributory liver toxicity.

Boron Neutron Capture Therapy (BNCT) Mediated by Maleimide-Functionalized Closo-Dodecaborate Albumin Conjugates (MID:BSA) for Oral Cancer: Biodistribution Studies and In Vivo BNCT in the Hamster Cheek Pouch Oral Cancer Model.

BACKGROUND: BNCT (Boron Neutron Capture Therapy) is a tumor-selective particle radiotherapy that combines preferential boron accumulation in tumors and neutron irradiation. Although p-boronophenylalanine (BPA) has been clinically used, new boron compounds are needed for the advancement of BNCT. Based on previous studies in colon tumor-bearing mice, in this study, we evaluated MID:BSA (maleimide-functionalized closo-dodecaborate conjugated to bovine serum albumin) biodistribution and MID:BSA/BNCT therapeutic effect on tumors and associated radiotoxicity in the hamster cheek pouch oral cancer model. METHODS: Biodistribution studies were performed at 30 mg B/kg and 15 mg B/kg (12 h and 19 h post-administration). MID:BSA/BNCT (15 mg B/kg, 19 h) was performed at three different absorbed doses to precancerous tissue. RESULTS: MID:BSA 30 mg B/kg protocol induced high BSA toxicity. MID:BSA 15 mg B/kg injected at a slow rate was well-tolerated and reached therapeutically useful boron concentration values in the tumor and tumor/normal tissue ratios. The 19 h protocol exhibited significantly lower boron concentration values in blood. MID:BSA/BNCT exhibited a significant tumor response vs. the control group with no significant radiotoxicity. CONCLUSIONS: MID:BSA/BNCT would be therapeutically useful to treat oral cancer. BSA toxicity is a consideration when injecting a compound conjugated to BSA and depends on the animal model studied.

Boron neutron capture therapy (BNCT) for the treatment of liver metastases: biodistribution studies of boron compounds in an experimental model.

We previously demonstrated the therapeutic efficacy of different boron neutron capture therapy (BNCT) protocols in an experimental model of oral cancer. BNCT is based on the selective accumulation of (10)B carriers in a tumor followed by neutron irradiation. Within the context of exploring the potential therapeutic efficacy of BNCT for the treatment of liver metastases, the aim of the present study was to perform boron biodistribution studies in an experimental model of liver metastases in rats. Different boron compounds and administration conditions were assayed to determine which administration protocols would potentially be therapeutically useful in in vivo BNCT studies at the RA-3 nuclear reactor. A total of 70 BDIX rats were inoculated in the liver with syngeneic colon cancer cells DHD/K12/TRb to induce the development of subcapsular tumor nodules. Fourteen days post-inoculation, the animals were used for biodistribution studies. We evaluated a total of 11 administration protocols for the boron compounds boronophenylalanine (BPA) and GB-10 (Na(2)(10)B(10)H(10)), alone or combined at different dose levels and employing different administration routes. Tumor, normal tissue, and blood samples were processed for boron measurement by atomic emission spectroscopy. Six protocols proved potentially useful for BNCT studies in terms of absolute boron concentration in tumor and preferential uptake of boron by tumor tissue. Boron concentration values in tumor and normal tissues in the liver metastases model show it would be feasible to reach therapeutic BNCT doses in tumor without exceeding radiotolerance in normal tissue at the thermal neutron facility at RA-3.

Paget's disease of the jaws: Histopathological features of a series of 31 cases.

The aim of the present study was to analyze the histopathological features of Paget's disease of the jaws observed in a series comprising 31 cases. The study comprised all cases of Paget's disease of the jaws filed in the archives of the Surgical Pathology Laboratory of the Oral Pathology Department, School of Dentistry, University of Buenos Aires, between 1960 and 2018. Their microscopic features were evaluated, and available clinical data and radiographic studies were analyzed. Paget's disease of the jaws accounted for 0.05% of retrieved oral-maxillofacial pathologies. Microscopically, all cases showed lamellar bone trabeculae with the characteristic mosaic pattern. Twenty cases (64%) showed osteoblastic-osteoclastic activity, and all showed areas of necrosis. Cemento-osseous trabeculae were observed in 15 cases (48%), and cementicles were observed in 13 (42%). Osteomyelitis was seen in 11 cases (35%), all of which showed cemento-osseous trabeculae with a mosaic structure, sclerosis and necrosis, and chronic inflammation with abscess formation. Mean age was 61 years (44-85 years); 19 cases were women. Localization was the maxilla in 13 cases (42%), and the disease involved other skeletal bones in five cases. To our knowledge, this is the largest series of Paget's disease of the jaws reported to date. Paget's disease is infrequent in the jaws and has distinct histopathological features that not only differ from those observed at other skeletal sites but also require differential diagnosis from other pathologies affecting the jaws exclusively.

El objetivo del presente trabajo fue analizar las características histopatológicas de la enfermedad de Paget en los maxilares en una serie de 31 casos. El estudio comprendió todos los casos de enfermedad de Paget de los maxilares provenientes del Laboratorio de Patología Quirúrgica de la Cátedra de Anatomía Patológica de la Facultad de Odontología de la Universidad de Buenos Aires, entre 1960 y 2018. Se evaluaron las características microscópicas y se analizaron los datos clínicos y estudios radiográficos disponibles. La enfermedad de Paget en los maxilares representó el 0,05% de las patologías buco-maxilofaciales. Microscópicamente, todos los casos mostraron trabéculas óseas laminares con el característico patrón en mosaico. Veinte casos (64%) mostraron actividad osteoblástica-clástica y todos los casos mostraron necrosis focal. En 15 casos (48%) las trabéculas presentaron aspecto cemento-óseo y en 13 casos (42%) se observaron cementículos. Once casos (35%) presentaron cuadros osteomielíticos y todos ellos mostraron trabéculas cemento-óseas con estructura en mosaico, esclerosis y necrosis, e infiltrado inflamatorio crónico con formación de abscesos. La media de edad fue 61 años (44-85 años), y 19 fueron mujeres. Trece casos (42%) se localizaron en maxilar superior y 5 casos presentaron compromiso de otros huesos. A nuestro entender, esta es la serie más grande de enfermedad de Paget en los maxilares reportada hasta la fecha. La enfermedad de Paget es poco frecuente en los maxilares y presenta características histopatológicas que además de ser diferentes a las observadas en otros sitios del esqueleto plantean el diagnóstico diferencial con otras entidades que se presentan exclusivamente en los maxilares.

Evaluation of local, regional and abscopal effects of Boron Neutron Capture Therapy (BNCT) combined with immunotherapy in an ectopic colon cancer model.

OBJECTIVE: The aim of the present study was to evaluate the local and regional therapeutic efficacy and abscopal effect of BNCT mediated by boronophenyl-alanine, combined with Bacillus Calmette-Guerin (BCG) as an immunotherapy agent in this model. METHODS: The local effect of treatment was evaluated in terms of tumor response in the irradiated tumor-bearing right hind flank. Metastatic spread to tumor-draining lymph nodes was analyzed as an indicator of regional effect. The abscopal effect of treatment was assessed as tumor growth inhibition in the contralateral (non-irradiated) left hind flank inoculated with tumor cells 2 weeks post-irradiation. The experimental groups BNCT, BNCT + BCG, BCG, Beam only (BO), BO +BCG, SHAM (tumor-bearing, no treatment, same manipulation) were studied. RESULTS: BNCT and BNCT + BCG induced a highly significant local anti-tumor response, whereas BCG alone induced a weak local effect. BCG and BNCT + BCG induced a significant abscopal effect in the contralateral non-irradiated leg. The BNCT + BCG group showed significantly less metastatic spread to tumor-draining lymph nodes vs SHAM and vs BO. CONCLUSION: This study suggests that BNCT + BCG-immunotherapy would induce local, regional and abscopal effects in tumor-bearing animals. BNCT would be the main effector of the local anti-tumor effect whereas BCG would be the main effector of the abscopal effect. ADVANCES IN KNOWLEDGE: Although the local effect of BNCT has been widely evidenced, this is the first study to show the local, regional and abscopal effects of BNCT combined with immunotherapy, contributing to comprehensive cancer treatment with combined therapies.

Publication: Presentation rate in the Latin American region of the International Association for Dental Research.

Most research conducted by the dental scientific community is presented at the Annual Meetings of the different Divisions and Sections of IADR. This research acquires real value when the results are published in peer-reviewed journals. A useful indicator of the publication efficiency of research work is the rate of publication (PR), i.e., the ratio between the quantity of presentations and subsequent publications in peer-reviewed journals. The aim of this study was to analyze the PR of the presentations at the Sections and Divisions of the Latin American Region of the International Association for Dental Research (IADR). We considered the presentations at the Annual Meetings of Argentina, Brazil, Chile and Peru held in 2002 and 2003 and their corresponding publications indexed in PubMed from 2002 to 2009. For Venezuela, we analyzed the meetings held in 2002 and 2005, because they did not hold consecutive annual meetings. Presentation periods were selected based on previous data that report an interval of up to five years between presentation and publication. The number of presentations and the PR are related to the number of years that Sections and Divisions have existed. In Brazil and Argentina, PR (expressed as 1 publication: x presentations) is 1:3. The amount of research in Brazil is almost 8 times higher than in Argentina. Newer Sections and Divisions have produced fewer presentations, and the PR is also lower. We hope that this type of analysis will encourage the promotion of dental research at the different institutions and in the different vacancy areas of research, and facilitate exchange among researchers in the Region, enabling greater use to be made of their scientific activities.

Insight into the mechanisms underlying tumor response to boron neutron capture therapy in the hamster cheek pouch oral cancer model.

OBJECTIVE: The therapeutic success of different boron neutron capture therapy (BNCT) protocols employing the hamster cheek pouch oral cancer model has been previously reported by our laboratory. The aim of this study was to explore potential mechanisms of BNCT-induced damage to tumor in terms of potential inhibition in DNA synthesis and induction of apoptosis in the tumors that underwent partial remission following application of the different BNCT protocols in this model. MATERIALS AND METHODS: We evaluated DNA synthesis employing incorporation of 5-bromo-2'-deoxyuridine as an end-point. Apoptosis was evaluated by immunohistochemistry employing the deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end-labeling technique and Bax and Bcl-2 labeling. These studies were performed in tumors that underwent partial remission 1-30 days post-BNCT mediated by boronophenylalanine (BPA), GB-10 (Na(2)(10)B(10)H(10)) or (BPA + GB-10). RESULTS: BNCT exerted a marked inhibitory effect on DNA synthesis in tumors for all the protocols under study. The inhibitory effect of BPA-BNCT occurred as soon as 1 day post-treatment (P < 0.001). Conversely, the effect of GB-10-BNCT became apparent 7-14 days after therapy (P < 0.001) and was sustained until killed at 30 days post-treatment (P < 0.001). (GB-10 + BPA)-BNCT exerted a rapid and persistent effect, conceivably because of the combined effect of BNCT mediated by both boron compounds. The apoptosis studies did not show differences between the pre-treatment group and any of the BNCT groups. CONCLUSIONS: One of the mechanisms involved in BNCT-induced tumor control in our model would be an inhibitory effect on DNA synthesis. Apoptosis does not seem to have a significant role in BNCT-induced tumor control in our model.

Different oral cancer scenarios to personalize targeted therapy: Boron Neutron Capture Therapy translational studies.

Boron neutron capture therapy (BNCT) is a targeted therapy, which consists of preferential accumulation of boron carriers in tumor followed by neutron irradiation. Each oral cancer patient has different risks of developing one or more carcinomas and/or oral mucositis induced after treatment. Our group proposed the hamster oral cancer model to study the efficacy of BNCT and associated mucositis. Translational studies are essential to the advancement of novel boron delivery agents and targeted strategies. Herein, we review our work in the hamster model in which we studied BNCT induced mucositis using three different cancerization protocols, mimicking three different clinical scenarios. The BNCT-induced mucositis increases with the aggressiveness of the carcinogenesis protocol employed, suggesting that the study of different oral cancer patient scenarios would help to develop personalized therapies.

Translational boron neutron capture therapy (BNCT) studies for the treatment of tumors in lung.

PURPOSE: Boron neutron capture therapy (BNCT) combines selective accumulation of 10B carriers in tumor tissue with subsequent neutron irradiation. BNCT has been proposed for the treatment of multiple, non-resectable, diffuse tumors in lung. The aim of the present study was to evaluate the therapeutic efficacy and toxicity of BNCT in an experimental model of lung metastases of colon carcinoma in BDIX rats and perform complementary survival studies. MATERIALS AND METHODS: We evaluated tumor control and toxicity in lung 2 weeks post-BNCT at 2 dose levels, including 5 experimental groups per dose level: T0 (euthanized pre-treatment), Boronophenylalanine-BNCT (BPA-BNCT), BPA + Sodium decahydrodecaborate-BNCT ((BPA + GB-10)-BNCT), Beam only (BO) and Sham (no treatment, same manipulation). Tumor response was assessed employing macroscopic and microscopic end-points. An additional experiment was performed to evaluate survival and oxygen saturation in blood. RESULTS AND CONCLUSIONS: No dose-limiting signs of short/medium-term toxicity were observed in lung. All end-points revealed statistically significant BNCT-induced tumor control vs Sham at both dose levels. The survival experiment showed a statistically significant 45% increase in post-treatment survival time in the BNCT group (48 days) versus Sham (33 days). These data consistently revealed growth suppression of lung metastases by BNCT with no manifest lung toxicity. Highlights Boron Neutron Capture Therapy suppresses growth of experimental lung metastases No BNCT-induced short/medium-term toxicity in lung is associated with tumor control Boron Neutron Capture Therapy increased post-treatment survival time by 45.

Effect of Boron Neutron Capture Therapy (BNCT) on normal liver regeneration: towards a novel therapy for liver metastases.

PURPOSE: The effect of Boron Neutron Capture Therapy (BNCT) on normal liver regeneration was examined in the Wistar rat. The model used is clinically relevant to a novel technique proposed for the treatment of multifocal non-resectable liver metastases in man. The success of the technique also requires that BNCT should not significantly impair regeneration of normal hepatocytes. MATERIALS AND METHODS: The effect of therapeutic doses of boronophenylalanine (BPA), GB-10 (Na(2)(10)B(10)H(10)) and (GB-10 + BPA) and of BNCT mediated by these boron delivery agents on normal liver regeneration and liver function in the Wistar rat was examined using partial hepatectomy as the regenerative stimulus. The end-points evaluated were body weight, liver weight/body weight ratio, DNA synthesis in terms of 5-bromo-2'-deoxyuridine incorporation, hemogram, kidney function in terms of blood urea nitrogen and creatinine levels, liver function in terms of serum albumin, total and direct bilirubin and liver enzymes (alanine transaminase and aspartate transaminase) and liver histology/architecture. RESULTS: BNCT mediated by BPA, GB-10 or (GB-10 + BPA) did not cause alterations in the outcome of normal liver regeneration, regenerated liver function/proliferation or histology/architecture. CONCLUSION: The BNCT protocols, at the physical doses selected, did not impair the capacity of normal liver hepatocytes to regenerate.

Therapeutic effect of boron neutron capture therapy (BNCT) on field cancerized tissue: inhibition of DNA synthesis and lag in the development of second primary tumors in precancerous tissue around treated tumors in DMBA-induced carcinogenesis in the hamster cheek pouch oral cancer model.

OBJECTIVE: We previously reported the therapeutic success of different BNCT protocols in the treatment of oral cancer, employing the hamster cheek pouch model. The aim of the present study was to evaluate the effect of these BNCT protocols on DNA synthesis in precancerous and normal tissue in this model and assess the potential lag in the development of second primary tumors in precancerous tissue. The data are relevant to potential control of field cancerized tissue and tolerance of normal tissue. MATERIALS AND METHODS: We evaluated DNA synthesis in precancerous and normal pouch tissue 1-30 days post-BNCT mediated by boronophenylalanine (BPA), GB-10 (Na(2)(10)B(10)H(10)) or (BPA+GB-10) employing incorporation of 5-bromo-2'-deoxyuridine as an end-point. The BNCT-induced potential lag in the development of second primary tumors from precancerous tissue was monitored. RESULTS: A drastic, statistically significant reduction in DNA synthesis occurred in precancerous tissue as early as 1 day post-BNCT and was sustained at virtually all time-points until 30 days post-BNCT for all the protocols. The histological categories evaluated individually within precancerous tissue (dysplasia, hyperplasia and NUMF [no unusual microscopic features]) responded similarly. DNA synthesis in normal tissue treated with BNCT oscillated around the very low pre-treatment values. A BNCT-induced lag in the development of second primary tumors was observed. CONCLUSIONS: BNCT induced a drastic fall in DNA synthesis in precancerous tissue that would be associated to the observed lag in the development of second primary tumors. The minimum variations in DNA synthesis in BNCT-treated normal tissue would correlate with the absence of normal tissue radiotoxicity. The present data would support the control of field-cancerized areas by BNCT.

Therapeutic success of boron neutron capture therapy (BNCT) mediated by a chemically non-selective boron agent in an experimental model of oral cancer: a new paradigm in BNCT radiobiology.

The hypothesis of boron neutron capture therapy (BNCT) research has been that the short-range, high-linear energy transfer radiation produced by the capture of thermal neutrons by (10)B will potentially control tumor and spare normal tissue only if the boron compound selectively targets tumor tissue within the treatment volume. In a previous in vivo study of low-dose BNCT mediated by GB-10 (Na(2)(10)B(10)H(10)) alone or combined with boronophenylalanine (BPA) in the hamster cheek pouch oral cancer model that was primarily designed to evaluate safety and feasibility, we showed therapeutic effects but no associated normal tissue radiotoxicity. In the present study, we evaluated the response of tumor, precancerous and normal tissue to high-dose BNCT mediated by GB-10 alone or combined with BPA. Despite the fact that GB-10 does not target hamster cheek pouch tumors selectively, GB-10-BNCT induced a 70% overall tumor response with no damage to normal tissue. (GB-10+BPA)-BNCT induced a 93% overall tumor response with no normal tissue radiotoxicity. Light microscope analysis showed that GB-10-BNCT selectively damages tumor blood vessels, sparing precancerous and normal tissue vessels. In this case, selective tumor lethality would thus result from selective blood vessel damage rather than from selective uptake of the boron compound.

Homogeneous boron targeting of heterogeneous tumors for boron neutron capture therapy (BNCT): chemical analyses in the hamster cheek pouch oral cancer model.

OBJECTIVE: BNCT is a tumour cell targeted radiation therapy. Uniform targeting of heterogeneous tumours with therapeutically effective boron carriers would contribute to a therapeutic effect on all tumour cell populations and avoid radioresistant fractions. This remains an unresolved challenge. The aim of the present study was to evaluate the degree of variation in boron content delivered by boronophenylalanine (BPA), GB-10 (Na(2)(10)B(10)H(10)) and the combined administration of (BPA+GB-10) in different portions of tumour, precancerous tissue around tumour and normal pouch tissue in the hamster cheek pouch oral cancer model. MATERIALS AND METHODS: Samples of different areas of tumour, precancerous tissue and normal pouch tissue were taken from tumour-bearing hamsters, 3h post-administration of i.p. BPA (15.5mg B/kg b.w.), or i.v. GB-10 (50mg B/kg b.w.), or 3h and 1.5h post-administration respectively of i.v. GB-10 (34.5mg B/b.w.) and sequential i.p. injections of BPA (total dose 31mg B/kg b.w.) given jointly. Boron content was evaluated by inductively coupled plasma optical emission spectroscopy (ICP-OES). The degree of homogeneity in boron targeting was assessed in terms of the coefficient of variation (V: [S.D./mean]x100) of boron values. Statistical analysis of the results was performed by one-way ANOVA and the least significant difference test. RESULTS: GB-10 and GB-10 plus BPA achieved respectively a statistically significant 1.8- and 3.3-fold increase in targeting homogeneity over BPA. CONCLUSIONS: The combined boron compound administration protocol contributes to homogeneous targeting of heterogeneous tumours and would be expected to increase therapeutic efficacy of BNCT.