Tumor Treating Fields (TTFields) Plus Sorafenib Is Safe and Effective in Hepatocellular Carcinoma Tested in Vitro and in an Animal Model

Abstract

Hepatocellular carcinoma (HCC) is the third cause of cancer related mortality. Sorafenib, an oral multikinase inhibitor is approved for patients with advanced HCC, however its survival benefit is reportedly limited. Tumor Treating Fields (TTFields) therapy is an effective anti-neoplastic treatment modality delivered via noninvasive application of low intensity, intermediate frequency, alternating electric fields. The aim of this work is to explore the potential use of TTFields alone and in combination with Sorafenib as a treatment for HCC. HepG2 and Huh-7D12 HCC cells were treated with various TTFields frequencies (100-400 kHz) for 72 hours using the inovitro system. Efficacy of the combined treatment of TTFields and Sorafenib was tested by applying TTFields at the optimal frequency together with various Sorafenib concentrations. Cell counts, induction of apoptosis and clonogenic potential were determined. N1S1 HCC cells were injected to the left lobe of the liver of Sprague Dawley rats. After 1 week, TTFields (1.2 V/cm) and Sorafenib (10 mg/kg) were applied for 6 days and tumor growth was evaluated using MRI. Healthy rats were used to study the safety of the use of TTFields (150 kHz) applied to the abdomen. The optimal frequency of TTFields was 150 kHz for both cell lines. TTFields application (1.0 - 1.7 V/cm, 72 hours) at 150 kHz led to 53-55% reduction in cell counts and to additional reduction (65-69%) in clonogenic potential. The combination of TTFields and Sorafenib led to a significant reduction in cell count (2-way ANOVA, p<0.05) as compared to either treatment alone. Tumor growth was significantly reduced in the combined group compared to the control group (student t test, p<0.01). On average, the tumor volume fold increase in the combination treatment group (1.6) was significantly lower than the control group (5.9, p <0.0001), TTFields group (3.3, p <0.01) and the Sorafenib group (2.3, p <0.05). Safety studies did not reveal any adverse event associated with TTFields application to the rat abdomen. These results demonstrate that TTFields can be a safe and effective treatment against HCC cells and that the combination with Sorafenib leads to a further enhancement of the treatment efficacy. Based on these results a Phase 2 trial in HCC of TTFields and Sorafenib is planned (HEPANOVA NCT03606590).