Interventional Oncolytic Immunotherapy with LTX-315 for Residual Tumor after Incomplete Radiofrequency Ablation of Liver Cancer

Objective: To investigate the feasibility of interventional oncolytic immunotherapy with LTX-315 for residual tumors after incomplete radiofrequency ablation (iRFA) of VX2 liver tumors in a rabbit model. Methods: For in vitro experiments, VX2 tumor cells were treated with: (1) phosphate buffered saline, (2) radiofrequency hyperthermia (RFH), (3) LTX-315, and (4) RFH plus LTX-315. The residual tumors after iRFA of VX2 liver tumors were treated with: (1) phosphate buffered saline served as control, (2) 2 mg LTX-315, and (3) 4 mg LTX-315. MTS assay, fluorescence microscopy, and flow cytometry were used to compare cell viabilities and apoptosis among different groups. Ultrasound imaging was used to follow up the tumor growth, which were correlated with the optical imaging and subsequent histology. Results: For in vitro experiments, compared with the other three groups, MTS assay demonstrated the lowest cell viability, fluorescence microscopy showed the least survival cells, and apoptosis analysis revealed the highest percentage of apoptosis cells in the combination treatment groups (p < 0.001). For in vivo experiments, ultrasound imaging showed the smallest tumor volume in the group with 4 mg LTX-315 therapy compared with the other two groups (p < 0.001). The optical imaging and histopathological analysis showed complete necrosis of the tumors in the group with 4 mg LTX-315 therapy. A significant increase of CD8+ T cells and HSP70 and a significant decrease of Tregs were observed in residual tumors in the group with 2 mg LTX-315 therapy compared with the control group (p < 0.001). Conclusion: Interventional oncolytic immunotherapy with LTX-315 for residual tumors after iRFA of liver cancer is feasible, which may open up new avenues to prevent residual tumors after RFA of intermediate-to-large liver cancers.

Development of a Three-Dimensional Multi-Modal Perfusion-Thermal Electrode System for Complete Tumor Eradication

Background: Residual viable tumor cells after ablation at the tumor periphery serve as the source for tumor recurrence, leading to treatment failure. Purpose: To develop a novel three-dimensional (3D) multi-modal perfusion-thermal electrode system completely eradicating medium-to-large malignancies. Materials and Methods: This study included five steps: (i) design of the new system; (ii) production of the new system; (iii) ex vivo evaluation of its perfusion-thermal functions; (iv) mathematic modeling and computer simulation to confirm the optimal temperature profiles during the thermal ablation process, and; (v) in vivo technical validation using five living rabbits with orthotopic liver tumors. Results: In ex vivo experiments, gross pathology and optical imaging demonstrated the successful spherical distribution/deposition of motexafin gadolinium administered through the new electrode, with a temperature gradient from the electrode core at 80 °C to its periphery at 42 °C. An excellent repeatable correlation of temperature profiles at varying spots, from the center to periphery of the liver tumor, was found between the mathematic simulation and actual animal tumor models (Pearson coefficient ≥0.977). For in vivo validation, indocyanine green (ICG) was directly delivered into the peritumoral zones during simultaneous generation of central tumoral lethal radiofrequency (RF) heat (>60 °C) and peritumoral sublethal RF hyperthermia (<60 °C). Both optical imaging and fluorescent microscopy confirmed successful peritumoral ICG distribution/deposition with increased heat shock protein 70 expression. Conclusion: This new 3D, perfusion-thermal electrode system provided the evidence on the potential to enable simultaneous delivery of therapeutic agents and RF hyperthermia into the difficult-to-treat peritumoral zones, creating a new strategy to address the critical limitation, i.e., the high incidence of residual and recurrent tumor following thermal ablation of unresectable medium-to-large and irregular tumors.

Preclinical Studies in Small Animals for Advanced Drug Delivery Using Hyperthermia and Intravital Microscopy

This paper presents three devices suitable for the preclinical application of hyperthermia via the simultaneous high-resolution imaging of intratumoral events. (Pre)clinical studies have confirmed that the tumor micro-environment is sensitive to the application of local mild hyperthermia. Therefore, heating is a promising adjuvant to aid the efficacy of radiotherapy or chemotherapy. More so, the application of mild hyperthermia is a useful stimulus for triggered drug release from heat-sensitive nanocarriers. The response of thermosensitive nanoparticles to hyperthermia and ensuing intratumoral kinetics are considerably complex in both space and time. To obtain better insight into intratumoral processes, longitudinal imaging (preferable in high spatial and temporal resolution) is highly informative. Our devices are based on (i) an external electric heating adaptor for the dorsal skinfold model, (ii) targeted radiofrequency application, and (iii) a microwave antenna for heating of internal tumors. These models, while of some technical complexity, significantly add to the understanding of effects of mild hyperthermia warranting implementation in research on hyperthermia.

Image-Guided Peri-Tumoral Radiofrequency Hyperthermia-Enhanced Direct Chemo-Destruction of Hepatic Tumor Margins

Purpose

To validate the feasibility of using peri-tumoral radiofrequency hyperthermia (RFH)-enhanced chemotherapy to obliterate hepatic tumor margins.

Method and Materials

This study included in vitro experiments with VX2 tumor cells and in vivo validation experiments using rabbit models of liver VX2 tumors. Both in vitro and in vivo experiments received different treatments in four groups (n=6/group): (i) RFH-enhanced chemotherapy consisting of peri-tumoral injection of doxorubicin plus RFH at 42°C; (ii) RFH alone; (iii) doxorubicin alone; and (iv) saline. Therapeutic effect on cells was evaluated using different laboratory examinations. For in vivo experiments, orthotopic hepatic VX2 tumors in 24 rabbits were treated by using a multipolar radiofrequency ablation electrode, enabling simultaneous delivery of both doxorubicin and RFH within the tumor margins. Ultrasound imaging was used to follow tumor growth overtime, correlated with subsequent histopathological analysis.

Results

In in vitro experiments, MTS assay demonstrated the lowest cell proliferation, and apoptosis analysis showed the highest apoptotic index with RFH-enhanced chemotherapy, compared with the other three groups (p<0.01). In in vivo experiments, ultrasound imaging detected the smallest relative tumor volume with RFH-enhanced chemotherapy (p<0.01). The TUNEL assay further confirmed the significantly increased apoptotic index and decreased cell proliferation in the RFH-enhanced therapy group (p<0.01).

Conclusion

This study demonstrates that peri-tumoral RFH can specifically enhance the destruction of tumor margins in combination with peri-tumoral injection of a chemotherapeutic agent. This new interventional oncology technique may address the critical clinical problem of frequent marginal tumor recurrence/persistence following thermal ablation of large (>3 cm) hepatic cancers.

Patient-Specific Planning for Thermal Magnetic Resonance of Glioblastoma Multiforme

Simple Summary

Hyperthermia was proven to enhance the efficacy of chemo- and radiation therapy treatment of glioblastoma multiforme, an aggressive brain tumor of poor prognosis. Despite good clinical results in other tumor types and locations, hyperthermia induced by electromagnetic waves in the radiofrequency range is not available so far for the treatment of brain tumors due to the highly sensitive surrounding tissue and lack of non-invasive therapy monitoring. ThermalMR integrates non-invasive diagnosis, therapy, and therapy monitoring in a single RF applicator device by employing radiowaves for magnetic resonance imaging, radiofrequency heating, as well as magnetic resonance thermometry. This work examines three optimization algorithms for hyperthermia treatment planning and up to ten RF applicator configurations for a cohort of nine patient models with glioblastoma multiforme. Clinical diversity is represented in target size and location and the inclusion of post-operative models. Our findings indicate the need and potential for patient-specific treatment planning and RF applicator design when targeting brain tumors.

Abstract

Thermal intervention is a potent sensitizer of cells to chemo- and radiotherapy in cancer treatment. Glioblastoma multiforme (GBM) is a potential clinical target, given the cancer’s aggressive nature and resistance to current treatment options. This drives research into optimization algorithms for treatment planning as well as radiofrequency (RF) applicator design for treatment delivery. In this work, nine clinically realistic GBM target volumes (TVs) for thermal intervention are compared using three optimization algorithms and up to ten RF applicator designs for thermal magnetic resonance. Hyperthermia treatment planning (HTP) was successfully performed for all cases, including very small, large, and even split target volumes. Minimum requirements formulated for the metrics assessing HTP outcome were met and exceeded for all patient specific cases. Results indicate a 16 channel two row arrangement to be most promising. HTP of TVs with a small extent in the cranial–caudal direction in conjunction with a large radial extent remains challenging despite the advanced optimization algorithms used. In general, deep seated targets are favorable. Overall, our findings indicate that a one-size-fits-all RF applicator might not be the ultimate approach in hyperthermia of brain tumors. It stands to reason that modular and reconfigurable RF applicator configurations might best suit the needs of targeting individual GBM geometry.

Image-Guided Radiofrequency Hyperthermia (RFH)-Enhanced Direct Chemotherapy of Hepatic Tumors: The Underlying Biomolecular Mechanisms

Purpose

To evaluate the treatment effect of radiofrequency-induced hyperthermia (RFH) combined with intra-tumoral chemotherapy for rabbit VX2 liver tumors and explore the underlying mechanism that drives local hyperthermia-enhanced chemotherapy.

Materials and Methods

VX2 cell lines and rabbits with liver VX2 tumors were randomly allocated to four treatment groups including: (1) combination therapy of Doxorubicin (DOX) plus hyperthermia/RFH (n=6); (2) DOX only; (3) hyperthermia/RFH only (n=6); and (4) phosphate-buffered saline-treated control (n=6). Cell viability and doxorubicin uptake by VX2 tumor cells were assayed using flow cytometry and fluorescence microscopy 24 h after treatments. Western blot was used to evaluate the expression level of heat shock protein 70 (HSP70) in tumor cells and tissues. For the harvested VX2 tumors, fluorescence microscopy was used to evaluate the distribution and penetration of doxorubicin in tumor tissues and HSP70 expression was analyzed by Western blot and immunohistochemistry.

Results

RFH enhanced the chemotherapeutic effect of doxorubicin in VX2 cells and rabbit liver VX2 tumors resulting in higher apoptosis and lower cell viability. Flowcytometry of VX2 cells showed more apoptotic cells in combination therapy of hyperthermia and DOX, compared with other three groups in-vitro experiments (45.80 ± 1.27% vs 20.66 ± 0.71%, vs 15.16 ± 0.81% and 0.62 ± 0.06%, respectively, p<0.01). The quantitative analysis by Western blot and immunohistochemistry showed increased expression of HSP70 in both VX2 tumor cells (1.28 ± 0.13 vs 0.64 ± 0.13 vs 0.83 ± 0.10 vs 0.15 ± 0.03, respectively, p<0.05) and tumors (1.47 ± 0.13 vs 0.51 ± 0.13 vs 0.74 ± 0.11 vs 0.16 ± 0.04, respectively, p <0.01). Fluorescence microscopy showed increased uptake of DOX in tumor cells in the combination therapy group.

Conclusions

RFH/hyperthermia enhanced the chemotherapeutic effect of DOX in VX2 tumors by promoting the uptake of DOX and the expression HSP70 in tumors.

Quantitative, Multi-institutional Evaluation of MR Thermometry Accuracy for Deep-Pelvic MR-Hyperthermia Systems Operating in Multi-vendor MR-systems Using a New Anthropomorphic Phantom

Clinical outcome of hyperthermia depends on the achieved target temperature, therefore target conformal heating is essential. Currently, invasive temperature probe measurements are the gold standard for temperature monitoring, however, they only provide limited sparse data. In contrast, magnetic resonance thermometry (MRT) provides unique capabilities to non-invasively measure the 3D-temperature. This study investigates MRT accuracy for MR-hyperthermia hybrid systems located at five European institutions while heating a centric or eccentric target in anthropomorphic phantoms with pelvic and spine structures. Scatter plots, root mean square error (RMSE) and Bland-Altman analysis were used to quantify accuracy of MRT compared to high resistance thermistor probe measurements. For all institutions, a linear relation between MRT and thermistor probes measurements was found with R² (mean ± standard deviation) of 0.97 ± 0.03 and 0.97 ± 0.02, respectively for centric and eccentric heating targets. The RMSE was found to be 0.52 ± 0.31 °C and 0.30 ± 0.20 °C, respectively. The Bland-Altman evaluation showed a mean difference of 0.46 ± 0.20 °C and 0.13 ± 0.08 °C, respectively. This first multi-institutional evaluation of MR-hyperthermia hybrid systems indicates comparable device performance and good agreement between MRT and thermistor probes measurements. This forms the basis to standardize treatments in multi-institution studies of MR-guided hyperthermia and to elucidate thermal dose-effect relations.

Penetration Depth in Nanoparticles Incorporated Radiofrequency Hyperthermia into the Tissue: Comprehensive Study with Histology and Pathology Observations

In present study, the effective penetration of radiofrequency (RF) induced gold decorated iron oxide nanoparticles (GS@IONPs) hyperthermia was investigated. The effective penetration depth of RF also the damage potency of hyperthermia was evaluated during histopathology observations which were done on the chicken breast tissue and hepatocellular carcinoma (HCC) models. The thermal damages are well- documented in our previous cellular study which was engaged with potency of RF hyperthermia in Epithelial adenocarcinoma (MCF-7) and fibroblast (L-929) cells deaths [1]. In recent work, PEGylated iron oxide nanoparticles (IONPs) were used as base platform for gold magnetic nanoparticles (GS@IONPs) formation. The 144.00015 MHz, 180W RF generator was applied for stimulating the nanoparticles. The chicken breast tissue and the hepatocellular tumor model was considered in the experimental section. In histology studies, the structural changes also the effective penetration depth of RF induced nanoparticles was observed through microscopic monitoring of the tissue slices in histology observations (Gazi medical school). The highest damage level was seen in 8.0 µm tissue slices where lower damages were seen in depth of 1.0 cm and more inside tissue. The histology observations clarified the effective penetration depth of RF waves and irreversible damages in the 2.0 cm inside the tissue.

Combinatorial effects of radiofrequency hyperthermia and radiotherapy in the presence of magneto-plasmonic nanoparticles on MCF-7 breast cancer cells

Here, the effects of combinatorial cancer therapy including radiotherapy (RT) and radiofrequency (RF) hyperthermia in the presence of gold-coated iron oxide nanoparticles (Au@IONPs), as a thermo-radio-sensitizer, are reported. The level of cell death and the ratio of Bax/Bcl2 genes, involved in the pathway of apoptosis, were measured to evaluate the synergistic effect of Au@IONPs-mediated RF hyperthermia and RT. MCF-7 human breast adenocarcinoma cells were treated with different concentrations of Au@IONPs. After incubation with NPs, the cells were exposed to RF waves (13.56 MHz; 100 W; 15 min). At the same time, thermometry was performed with an infrared (IR) camera. Then, the cells were exposed to 6 MV X-ray at various doses of 2 and 4 Gy. MTT (3-[4,5-dimethylthiazol-2-y1]-2,5-diphenyltetrazolium bromide) assay was performed to evaluate cell viability and quantitative real-time polymerase chain reaction (qRT-PCR) was used to determine the expression ratio of Bax/Bcl2. Cellular uptake of nanoparticles was confirmed qualitatively and quantitatively. The results obtained from MTT assay and qRT-PCR studies showed that NPs and RF hyperthermia had no significant effect when applied separately, while their combination had synergistic effects on cell viability percentage and the level of apoptosis induction. A synergistic effect was also observed when the cancer cells were treated with a combination of NPs, RF hyperthermia, and RT. On the basis of the obtained results, it may be concluded that the use of magneto-plasmonic NPs in the process of hyperthermia and RT of cancer holds a great promise to develop a new combinatorial cancer therapy strategy.

Orthotopic hepatocellular carcinoma: molecular imaging-monitored intratumoral hyperthermia-enhanced direct oncolytic virotherapy

Objective:

To validate the feasibility of molecular imaging-monitored intratumoral radiofrequency hyperthermia (RFH) enhanced direct oncolytic virotherapy for hepatocellular carcinoma (HCC).

Methods:

This study included in vitro experiments using luciferase-labeled rat HCC cells and in vivo validation experiments on rat models with orthotopic HCCs. Both cells and HCCs in four groups (n = 6/group) were treated by: (1) combination therapy of oncolytic virotherapy (T-VEC) plus RFH at 42 °C for 30 min; (2) oncolytic virotherapy alone; (3) RFH alone; and (4) saline. For in vitro confirmation, confocal microscopy and bioluminescence optical imaging were used to evaluate the cell viabilities. For in vivo validation, oncolytic viruses were directly infused into rat HCCs through a multi-functional perfusion-thermal RF electrode, followed by RFH. Ultrasound and optical imaging were used to follow up size and bioluminescence signal changes of tumors overtime, which were correlated with subsequent laboratory examinations.

Results:

For in vitro experiments, confocal microscopy showed the lowest number of viable cells, as well as a significant decrease of bioluminescence signal intensity of cells with combination therapy group, compared to other three groups (p < .001). For in vivo experiments, ultrasound and optical imaging showed the smallest tumor volume, and significantly decreased bioluminescence signal intensity in combination therapy group compared to other three groups (p < .05), which were well correlated with pathologic analysis.

Conclusion:

It is feasible of using molecular imaging to guide RFH-enhanced intratumoral oncolytic virotherapy of HCC, which may open new avenues to prevent residual or recurrent disease of thermally ablated intermediate-to-large HCCs.

Cholangiocarcinoma: molecular imaging-guided radiofrequency hyperthermia-enhanced intratumoral herpes simplex virus thymidine kinase gene therapy

We investigated the feasibility of using radiofrequency hyperthermia (RFH) to enhance green fluorescent protein (GFP)/herpes simplex virus thymidine kinase (HSV-TK)/ganciclovir (GCV) gene therapy of cholangiocarcinoma. Cholangiocarcinoma cells and mice with cholangiocarcinoma were treated by (i) GFP/HSV-TK/plasmid combined with RFH at 42°C, followed by ganciclovir administration; (ii) HSV-TK alone; (iii) RFH alone; and (iv) saline. The therapeutic effects among different treatments were evaluated by bioluminescent optical imaging and ultrasound imaging. For the technical validation, GFP/HSV-TK/plasmid was intrabiliarily injected into pig common bile duct (CBD) walls using a needle-integrated balloon catheter with or without RFH enhancement. GFP gene expression was evaluated by optical imaging, which was correlated with histology. The results show that combination therapy of HSV-TK plus RFH significantly induced lower cell viabilities and decreased bioluminescence signals compared the other three groups, which were further confirmed by the tumor volume decrease with combination therapy, as measured by ultrasound imaging. Optical imaging of CBD tissues demonstrated an increased GFP expression in the group with RFH enhancement, compared that with non-RFH treatment. We concluded that intratumoral RFH can enhance the therapeutic effect of GFP/HSV-TK/plasmid on cholangiocarcinoma, which may open new avenues for effective treatment of this deadly disease.

Radiofrequency hyperthermia promotes the therapeutic effects on chemotherapeutic-resistant breast cancer when combined with heat shock protein promoter-controlled HSV-TK gene therapy: Toward imaging-guided interventional gene therapy

Objective

Gene therapy is a frontier in modern medicine. In the present study, we explored a new technique for the effective treatment of multidrug-resistant (MDR) breast cancer by combining fully the advantages of multidisciplinary fields, including image-guided minimally invasive interventional oncology, radiofrequency technology, and direct intratumoral gene therapy.

Results

Combination treatment with P_HSP-TK plus RFH resulted in significantly higher TK gene transfection/expression, as well as a lower cell proliferation rate and a higher cell apoptosis index, than those of control groups. In vivo validation experiments with MRI confirmed that combination therapy resulted in a significant reduction of relative tumor volume compared with those of control animals, which was supported by the results of histologic and apoptosis analyses.

Materials and methods

The heat shock protein promoter (P_HSP) was used to precisely control the overexpression of thymidine kinase (TK) (P_HSP-TK). Serial in vitro experiments were performed to confirm whether radiofrequency hyperthermia (RFH) could enhance P_HSP-TK transfection and expression in a MDR breast cancer cell line (MCF7/Adr). Serial in vivo experiments were then carried out to validate the feasibility of the new technique, termed interventional RFH-enhanced direct intratumoral P_HSP-TK gene therapy. The therapeutic effect of combination therapy was evaluated by MRI and confirmed by subsequent laboratory correlation.

Conclusions

This study has established “proof-of-principle” of a new technique, interventional RFH-enhanced local gene therapy for MDR breast cancer, which may open new avenues for the effective management of MDR breast cancers via the simultaneous integration of interventional oncology, RF technology, and direct intratumoral gene therapy.

Orthotopic hepatic cancer: radiofrequency hyperthermia-enhanced intratumoral herpes simplex virus-thymidine kinase gene therapy

Purpose

To validate the feasibility of using interventional radiofrequency hyperthermia(RFH) to enhance herpes simplex virus-thymidine kinase (HSV-TK)/ganciclovir (GCV) gene therapy of rat orthotopic hepatic cancer.

Material and Methods

Rat hepatocellular carcinoma cells (MCA-RH-7777) were transduced with lentivirus/luciferase gene for optical imaging. In-vitro experiments with the luciferase cells and in-vivo experiments on rats with orthotopic hepatic tumors were divided into four treatment groups: (i) HSV-TK/GCV-mediated gene therapy combined with RFH; (ii) gene therapy alone; (iii) RFH alone; and (iv) phosphate buffered saline (PBS). Cell viability was evaluated by MTS assay and confocal microscopy, and HSV-TK gene expression in cells and tumors was quantified by western blotting. Bioluminescent optical imaging and ultrasound imaging were used to monitor and compare the photon signal and tumor size changes among different treatment groups overtime, respectively. The imaging findings were correlated with histology.

Results

For in-vitro experiments, the combination therapy group (gene therapy + RFH) demonstrated the lowest cell proliferation by MTS assay, compared to the gene therapy alone, RFH alone, and PBS (26.1±3.2% vs 50.4±4.6% vs 82.9±6.3% vs 100%, p<0.01). The combination therapy group also showed fewer survived cells by the confocal microscopy and the lowest bioluminescent signal by the optical imaging. For in-vivo experiments, the combination therapy group demonstrated a significantly decreased signal intensity on the bioluminescent optical imaging (0.57±0.09, 1.06±0.10 vs 3.43±0.27 vs 3.85±0.12, p<0.05) and smallest tumor volume by ultrasound imaging (0.28±0.11 vs 1.28±0.23vs 4.64±0.35 vs 6.37±0.36, p<0.05), compared to the other three groups. Additionally, these imaging findings correlated well with the histological confirmation.

Conclusion

It is feasible to use RFH to enhance HSV-TK/GCV gene therapy of hepatic tumors in in-vitro and in-vivo settings, as assessed by molecular imaging. This technical development may provide a novel opportunity for effective treatment of liver malignancies by employing simultaneous integration of radiofrequency technology, interventional oncology, and direct intratumoral gene therapy.

Radiofrequency hyperthermia-enhanced herpes simplex virus-thymidine kinase/ganciclovir direct intratumoral gene therapy of hepatocellular carcinoma

PURPOSE

To determine the feasibility of using radiofrequency hyperthermia (RFH) and to enhance the therapeutic effect of herpes simplex virus-thymidine kinase/ganciclovir (HSV-TK/GCV) for the treatment of hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

Human HCC cells (HepG2) were first transfected with lentivirus/luciferase. For both in vitro confirmation and in vivo validation, luciferase-labeled HCC cells and HCC tumour xenografts on mice received different treatments: (i) combination therapy of intratumoral HSV-TK/GCV-mediated gene therapy plus magnetic resonance imaging heating guidewire (MRIHG)-mediated RFH; (ii) gene therapy only; (iii) RFH only; and (iv) phosphate-buffered saline (PBS) as control. Cell proliferation was quantified. Tumour changes were monitored by ultrasound imaging and bioluminescence optical imaging before and at days 7 and 14 after treatments, which were correlated with subsequent histology.

RESULTS

In vitro, the lowest cell proliferation was seen in the combination therapy group compared with control groups (29 ± 6% vs. 56 ± 9%, 93 ± 4%, and 100 ± 5%, p < .05). Ultrasound imaging of treated animal xenografts showed smaller relative tumour volume in combination therapy group than those in three control groups (0.74 ± 0.19 vs. 1.79 ± 0.24, 3.14 ± 0.49 and 3.22 ± 0.52, p < .05). Optical imaging demonstrated significant decrease of bioluminescence signals of tumours in the combination therapy group, compared to those in three control groups (1.2 ± 0.1 vs. 1.9 ± 0.2% vs. 3.3 ± 0.6% vs. 3.5 ± 0.4%, p < .05). These imaging findings were correlated well with histologic confirmation.

CONCLUSION

RFH can enhance HSV-TK/GCV-mediated gene therapy of HepG2 cell line and mice human HCC xenografts, which may open new avenues for effective management of HCC using MR/RFH integrated interventional gene therapy.

Biological cell survival mapping for radiofrequency intracavitary hyperthermia combined with simultaneous high dose-rate intracavitary irradiation

We examined the best way to combine recently developed radiofrequency intracavitary hyperthermia with simultaneous high dose-rate intracavitary brachytherapy in an original experimental model. Temperature distribution was measured with an experimental phantom which was immersed in a water bath with the temperature controlled at 37 degrees C. Radiation dose distribution was calculated with a treatment-planning computer. Cell survival was measured by colony assay with HeLa-TG cells in vitro. Radiation dose response at 1 - 7 Gy and time response with hyperthermia in the range of 40 - 46 degrees C were estimated. Radiation dose-response curves in simultaneous treatment with hyperthermia for 30 min at 37 to 46 degrees C were estimated and the surviving fractions in combined treatment were plotted against temperature. For intracavitary radiation alone, cell survival rates increased with increasing distance from the source. For intracavitary hyperthermia alone, the maximum temperature was observed at a depth of 13 mm from the surface of the applicator under suitable treatment conditions. Homogeneous cell killing from the surface of the applicator to a tumor depth of 13 mm was observed under a specific treatment condition. Our experimental model is useful for evaluating the best simultaneous combined treatment.