Enhancing Ablation: Synergies with Regional and Systemic Therapies

Interventional Optical Imaging-Monitored Synergistic Effect of Radio-Frequency Hyperthermia and Oncolytic Immunotherapy

Purpose

To develop a new interventional oncology technique using indocyanine green (ICG)-based interventional optical imaging (OI) to monitor the synergistic effect of radiofrequency hyperthermia (RFH)-enhanced oncolytic immunotherapy.

Materials and Methods

This study included (1) optimization of ICG dose and detection time-window for intracellular uptake by VX2 tumor cells; (2) in-vitro confirmation of capability of using ICG-based OI to assess efficacy of RFH-enhanced oncolytic therapy (LTX-401) for VX2 cells; and (3) in-vivo validation of the interventional OI-monitored, intratumoral RFH-enhanced oncolytic immunotherapy using rabbit models with orthotopic liver VX2 tumors. Both in-vitro and in-vivo experiments were divided into four study groups (n=6/group) with different treatments: (1) combination therapy of RFH+LTX-401; (2) RFH alone at 42°C for 30 min; (3) oncolytic therapy with LTX-401; and (4) control with saline. For in-vivo validation, orthotopic hepatic VX2 tumors were treated using a new multi-functional perfusion-thermal radiofrequency ablation electrode, which enabled simultaneous delivery of both LTX-401 and RFH within the tumor and at the tumor margins.

Results

In in-vitro experiments, taking up of ICG by VX2 cells was linearly increased from 0 μg/mL to 100 μg/mL, while ICG-signal intensity (SI) reached the peak at 24 hours. MTS assay and apoptosis analysis demonstrated the lowest cell viability and highest apoptosis in combination therapy, compared to three monotherapies (P<0.005). In in-vivo experiments, ultrasound imaging detected the smallest relative tumor volume for the combination therapy, compared to other monotherapies (P<0.005). In both in-vitro and in-vivo experiments, ICG-based interventional optical imaging detected a significantly decreased SI in combination therapy (P<0.005), which was confirmed by the “gold standard” optical/X-ray imaging (P<0.05). Pathologic/laboratory examinations further confirmed the significantly decreased cell proliferation with Ki-67 staining, significantly increased apoptotic index with TUNEL assay, and significantly increased quantities of CD8 and CD80 positive cells with immunostaining in the combination therapy group, compared to other three control groups (P<0.005).

Conclusions

We present a new interventional oncology technique, interventional optical imaging-monitored RFH-enhanced oncolytic immunotherapy, which may open new avenues to effectively manage those patients with larger, irregular and unresectable malignancies, not only in liver but also the possibility in other organs.

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.

Development of an Electroporation and Nanoparticle-based Therapeutic Platform for Bone Metastases

Purpose To assess for nanopore formation in bone marrow cells after irreversible electroporation (IRE) and to evaluate the antitumoral effect of IRE, used alone or in combination with doxorubicin (DOX)-loaded superparamagnetic iron oxide (SPIO) nanoparticles (SPIO-DOX), in a VX2 rabbit tibial tumor model. Materials and Methods All experiments were approved by the institutional animal care and use committee. Five porcine vertebral bodies in one pig underwent intervention (IRE electrode placement without ablation [n = 1], nanoparticle injection only [n = 1], and nanoparticle injection followed by IRE [n = 3]). The animal was euthanized and the vertebrae were harvested and evaluated with scanning electron microscopy. Twelve rabbit VX2 tibial tumors were treated, three with IRE, three with SPIO-DOX, and six with SPIO-DOX plus IRE; five rabbit VX2 tibial tumors were untreated (control group). Dynamic T2*-weighted 4.7-T magnetic resonance (MR) images were obtained 9 days after inoculation and 2 hours and 5 days after treatment. Antitumor effect was expressed as the tumor growth ratio at T2*-weighted MR imaging and percentage necrosis at histologic examination. Mixed-effects linear models were used to analyze the data. Results Scanning electron microscopy demonstrated nanopores in bone marrow cells only after IRE (P , .01). Average volume of total tumor before treatment (503.1 mm³ ± 204.6) was not significantly different from those after treatment (P = .7). SPIO-DOX was identified as a reduction in signal intensity within the tumor on T2*-weighted images for up to 5 days after treatment and was related to the presence of iron. Average tumor growth ratios were 103.0% ± 75.8 with control treatment, 154.3% ± 79.7 with SPIO-DOX, 77% ± 30.8 with IRE, and -38.5% ± 24.8 with a combination of SPIO-DOX and IRE (P = .02). The percentage residual viable tumor in bone was significantly less for combination therapy compared with control (P = .02), SPIO-DOX (P , .001), and IRE (P = .03) treatment. The percentage residual viable tumor in soft tissue was significantly less with IRE (P = .005) and SPIO-DOX plus IRE (P = .005) than with SPIO-DOX. Conclusion IRE can induce nanopore formation in bone marrow cells. Tibial VX2 tumors treated with a combination of SPIO-DOX and IRE demonstrate enhanced antitumor effect as compared with individual treatments alone. ^© RSNA, 2017 Online supplemental material is available for this article.

Molecular bioluminescence imaging as a noninvasive tool for monitoring tumor growth and therapeutic response to MRI-guided laser ablation in a rat model of hepatocellular carcinoma

OBJECTIVES

The objective of this study was to quantitatively compare tumor imaging by magnetic resonance imaging (MRI) and molecular bioluminescence imaging (BLI) and test the feasibility of monitoring the effect of MRI-guided laser ablation on tumor viability by 2-dimensional BLI and 3-dimensional diffuse luminescence tomography (3D DLIT) in an orthotopic rat model of hepatocellular carcinoma.

MATERIALS AND METHODS

This study was approved by the animal care committee. Rats underwent injection of N1S1 cells stably transfected with an empty vector (n = 3) or a heat shock element luciferase reporter (HSE-luc; n = 4) into the liver. All rats underwent MRI to assess tumor establishment and volume and 2-dimensional BLI to assess tumor luminescence at day 7 with subsequent MRI and 2D BLI and 3D DLIT in select animals at days 14 and 21. Magnetic resonance imaging-guided laser ablation of the tumor was performed with preablation and postablation 2D BLI and/or 3D DLIT (n = 2). The tumors underwent histopathologic analysis to assess tumor viability.

RESULTS

The MRI scans demonstrated hyperintense T2-weighted lesions at 3 of 3 and 4 of 4 sites in the empty vector and HSE-luc rats, respectively. Two-dimensional BLI quantitation demonstrated 23.0-fold higher radiance in the HSE-luc group compared with the empty vector group at day 7 (P < 0.01) and a significant correlation with tumor volume by MRI (r = 0.86; P < 0.03). Tumor dimensions by 3D DLIT and MRI demonstrated good agreement. Three-dimensional DLIT quantitation demonstrated better agreement with the percentage of nonviable tumor by histopathology than did 2D BLI quantitation after the MRI-guided laser ablation.

CONCLUSIONS

Bioluminescence imaging is feasible as a noninvasive, quantitative tool for monitoring tumor growth and therapeutic response to thermal ablation in a rat model of hepatocellular carcinoma.

Locoregional therapy for hepatocellular carcinoma

Locoregional therapies for hepatocellular carcinoma have progressed greatly in the last 30 years, beginning with the introduction of chemoembolization. Embolization techniques have evolved with the use of drug-eluting beads and radioembolization with yttrium-90. In the last 10 years, several new ablation techniques were developed including radiofrequency ablation, microwave ablation, cryoablation, laser ablation, and irreversible electroporation. Isolated or in combination, these techniques have already shown that they can improve patient survival and/or provide acceptable palliation.

Hepatic arterial chemoembolization using drug-eluting beads in gastrointestinal neuroendocrine tumor metastatic to the liver

PURPOSE

This study was designed to evaluate short (<3 months) and intermediate-term (>3 months) follow-up in patients with metastatic neuroendocrine tumor to the liver who underwent hepatic arterial chemoembolization with drug-eluting beads at a single institution.

METHODS

Institutional review board approval was obtained for this retrospective review. All patients who were treated with 100-300 or 300-500 μm drug-eluting LC Beads (Biocompatibles, UK) preloaded with doxorubicin (range, 50-100 mg) for GI neuroendocrine tumor metastatic to the liver from June 2004 to June 2009 were included. CT and MRI were evaluated for progression using Response Evaluation Criteria In Solid Tumors (RECIST) or European Association for the Study of the Liver (EASL) criteria. Short-term (<3 months) and intermediate-term (>3 months) imaging response was determined and Kaplan-Meier survival curves were plotted.

RESULTS

Thirty-eight drug-eluting bead chemoembolization procedures were performed on 32 hepatic lobes, comprising 21 treatment cycles in 18 patients. All procedures were technically successful with two major complications (biliary injuries). At short-term follow-up (<3 months), 22 of 38 (58%) procedures and 10 of 21 (48%) treatment cycles produced an objective response (OR) with the remainder having stable disease (SD). At intermediate-term follow-up (mean, 445 days; range, 163-1247), 17 of 26 (65%) procedures and 8 of 14 (57%) treatment cycles produced an OR. Probability of progressing was approximately 52% at 1 year with a median time to progression of 419 days.

CONCLUSIONS

Drug-eluting bead chemoembolization is a reasonable alternative to hepatic arterial embolization and chemoembolization for the treatment of metastatic neuroendocrine tumor to the liver.