494eP Pharmacogenomic biomarkers and CNS progression in EGFR-mutant NSCLC patients treated with first-line osimertinib: A retrospective cohort study

Background: Tumor Treating Fields (TTFields) are alternating electric fields that disrupt cancer cell division and promote downstream immunogenic cell death (ICD), thereby stimulating antitumor immunity.TTFields, together with immune checkpoint inhibitors (ICIs) or docetaxel, are approved for metastatic non-small cell lung cancer (NSCLC) following progression on platinum-based chemotherapy, and are currently being evaluated in the first-line setting with ICIs and chemotherapy (LUNAR-2 trial; NCT06216301).This study examined TTFields alongside immunochemotherapy in preclinical NSCLC models.Methods: A549 human NSCLC cells were treated for 72 h with TTFields (150 kHz, 1.7 V/cm RMS) and/or cisplatin plus pemetrexed (CP).Cell count, apoptosis, and ICD markers surface calreticulin exposure and ATP depletion were evaluated.For in vivo studies, C57Bl/6 mice were orthotopically inoculated with LL/2 lung carcinoma cells.On day 7 mice were randomized into 4 groups: control, TTFields (continuously for 10 days), PCP (anti-PD-1 plus CP; 3 ip doses, every 72 h), or TTFields plus PCP.At study end tumors were measured and processed into single-cell suspensions for immune profiling.IFN- and granzyme B expression were assessed ex-vivo in PMA/ionomycin stimulated CD8 + T cells.Results: CP alone exerted limited cytotoxic effects and did not induce ICD in vitro at the tested concentrations.TTFields treatment on top of CP reduced cell counts, increased apoptosis, and enhanced the induction of ICD markers.In vivo, both TTFields and PCP reduced tumor growth relative to controls, while the concomitant application achieved the greatest tumor suppression.PCP, particularly with TTFields, increased tumor intratumoral CD3 + T cell-infiltration.CD8 + cells were preferentially increased and, in the TTFields + PCP group, displayed elevated IFN- and granzyme B production, consistent with enhanced cytotoxic immune activity.Conclusions: TTFields enhanced both antitumor activity and cytotoxic immune activation elicited by standard immunochemotherapy in preclinical NSCLC models, supporting their role as an immune-modulating therapeutic modality.