Oxidative DNA Damage Is Associated with Immune Remodeling and Therapeutic Response in High-Grade Serous Ovarian Cancer.

Background/Objectives: High-grade serous ovarian cancer (HGSOC) shows variable response to platinum-based neoadjuvant chemotherapy (NACT), with outcomes strongly linked to upfront treatment sensitivity. We evaluated whether oxidative DNA damage in pathologic samples is associated with improved clinical outcomes and reflects tumor-immune interactions. Methods: We analyzed matched pre- and post-NACT tumors from patients with stage III-IV HGSOC using Repair Assisted Damage Detection (RADD) to quantify total and oxidative DNA lesions (oxRADD). Gene expression profiling was performed on a subset of tumors using the NanoString PanCancer I/O 360. Associations with homologous recombination status, platinum sensitivity, recurrence, and survival were assessed. Results: Higher pre-NACT oxidative DNA damage was observed in tumors from patients who later recurred. Among recurrent tumors, elevated oxidative lesions were associated with improved overall survival (61.8 vs. 35.0 months; HR = 0.42, p = 0.037). Oxidative damage predicted recurrence (AUC = 0.71), supporting its utility in risk stratification. Tumors with serious oxidative damage showed reduced IDO1 and TGFβ signaling signatures, along with decreased B cell- and T cell-associated TIGIT signatures after NACT. Conclusions: These findings identify oxidative DNA damage as a potential pretreatment biomarker associated with recurrence, survival, and tumor-immune state, supporting its potential to impact therapeutic decision-making in HGSOC.