LAUSR

e20069 Background: Malignant pleural mesothelioma (MPM) is an aggressive thoracic cancer mostly linked to asbestos exposure. The standard of care (SOC) therapy for unresectable MPM is cisplatin plus pemetrexed. Treating Fields (TTFields) therapy is an effective anti-neoplastic treatment modality delivered via noninvasive application of low intensity, intermediate frequency, alternating electric fields. We explored the potential use of TTFields alone and in combination with SOC as a treatment for MPM. Methods: NCI-H2052 and MSTO-211H cells were treated at various TTFields frequencies for 72 hours using the inovitro system. The combined treatment of TTFields and cisplatin or pemetrexed was tested by applying TTFields at the optimal frequency together with various drug concentrations. Cell counts, clonogenic potential and induction of apoptosis were determined. TTFields (1.2 V/cm) were applied for 8 days to rats injected to the intrapleural cavity with IL-45 cells, and overall survival was tested. Results: TTFields optimal frequency was 150 kHz for both human cell lines. TTFields application (1.1 V/cm, 72 hours) at 150 kHz led to 45%-51% reduction in cell counts and 46-64%% additional reduction in clonogenic potential. The combined treatment of TTFields and cisplatin or pemetrexed led to a significant reduction in cell count, induction of apoptosis and reduced clonogenic potential as compared to each modality alone (p < 0.0001(. TTFields significantly prolonged the survival of rats compared to control group. Safety studies did not reveal any adverse events associated with 150 kHz TTFields application to the rat torso. Conclusions: These results demonstrate that TTFields can be an effective treatment against mesothelioma and the combination with cisplatin or pemetrexed may further enhance treatment efficacy. These results are in consistency with the recent phase 2 study (EF-23 trial) that showed improved overall survival for combined treatment as compared to historical control with no increase in systemic toxicity.