(F-218) Overall survival is improved in a rodent glioma model with High-Frequency Irreversible Electroporation: Evaluating monotherapy and combinatorial therapy approaches.

Introduction:: Glioblastoma multiforme (GBM) has an average 5-year survival rate of 6.8 percent¹. The inability of large therapeutic molecules to pass through the blood-brain barrier (BBB) and the migration of highly invasive GBM cells beyond the solid tumor boundary are significant obstacles in the treatment of GBM. In this study, we employ a tissue ablation technique known as high frequency irreversible electroporation² (H-FIRE) to treat glioblastoma in an orthotopic rodent glioma model. In addition to H-FIRE’s ability to induce non-thermal cell death, it has also demonstrated its ability to transiently disrupt the BBB, opening up the potential for enhanced drug perfusion into the brain. Here, we study the ablative effects of H-FIRE as a monotherapy and the synergistic effects of combinatorial liposomal doxorubicin (Lipodox) on rodent survival.


Materials and Methods:: Rodent glioma F98 cells were orthotopically implanted in 34 male Fischer rat brains. To investigate the effects of H-FIRE as a mono and combinatorial therapy, two H-FIRE protocols were investigated. The first was a high dose protocol whose intention was to induce near 100% ablation coverage of the tumor volume (subsequently inducing complete coverage of BBB disruption inducing fields as BBB disruption is a low field phenomenon compared to tissue ablation). The second protocol was a low dose protocol whose intention was to induce 100% BBB disruption coverage on the tumor while minimizing ablation strength fields (reduced to 6.8% coverage) to elucidate the therapeutic effects of BBB disruption fields alone in conjunction with a delivered chemotherapeutic (Liposomal Doxorubicin). Rodents received one of six experimental protocols: High Dose H-FIRE (HD-HFIRE) receiving an applied voltage of 525 V, Low Dose H-FIRE (LD-HFIRE) receiving an applied voltage of 180 V, HD-HFIRE + Lipodox (HD-HFIRE+DOX) receiving an IP injection of 5mg/kg Lipodox in addition to the HD-HFIRE protocol, and LD-HFIRE+Lipodox (LD-HFIRE+DOX) receiving an IP injection of 5mg/kg Lipodox in addition to the LD-HFIRE protocol. Additionally, a no treatment sham group was used for comparison, in which rodents received surgical implantation of needle electrodes, but no field was applied. H-FIRE protocols were delivered via a 2-needle configuration with a 3 mm separation and a 2.5 mm electrode exposure.


Results, Conclusions, and Discussions:: RESULTS

The median survival for each cohort is as follows: 31 days (HD-HFIRE), 38 days (LD-HFIRE), 37.5 days (HD-H-FIRE+ DOX), 27 days (LD-H-FIRE+DOX), and 26 days (sham). Kaplan-Meier survival curves are presented in Figure 1. A statistically greater overall survival fraction was noted in the high dose H-FIRE + liposomal doxorubicin (50%, p = 0.044), high dose H-FIRE (28.6%, p = 0.034), and the low dose H-FIRE (20%, p = 0.0214) groups compared to the sham control (0%).



DISCUSSION:

As improved overall survival and median survival were seen in all rodents whose treatment protocol included H-FIRE therapy when compared against the sham group, our findings suggest that H-FIRE therapy in the brain extends overall survival time. Meanwhile, the reduction of survival in the LD-HFIRE+DOX group may indicate that the BBB may not have been sufficiently disrupted with this protocol causing the drug to systemically circulate, primarily targeting healthy anatomy while the tumor was left to grow.



CONCLUSIONS

This study has demonstrated the efficacy of applying H-FIRE as both a monotherapy and as a combinatorial (liposomal doxorubicin) therapy for the treatment of brain tumors. Our results show that H-FIRE mediation in the treatment of rat gliomas significantly improves the median survival while demonstrating a potential for greater overall survival when leveraging it as a combinatorial therapy. While H-FIRE can be effectively used as a monotherapy to target the tumor on its own, the surrounding volumes of BBB disruption that facilitate drug delivery into the brain and the reversible electroporation regions that enhance drug uptake into the cells may further enhance the therapeutic effects.


Acknowledgements (Optional): : This study was supported in part by the NIH P01 (P01CA207206) and the Virginia Research Investment Fund (VRIF). Sabrina is funded by the ICTAS Doctoral Fellowship at Virginia Tech and the P.E.O Scholarship.


References (Optional): : [1] Ostrom, et al. 2019. Neuro-oncology

[2] Arena, et al. 2010. BioMedical Engineering Online