Health system inequities as a mediator of age-related survival differences in high-grade serous ovarian cancer: Chile as a case study for Latin America.

e17597 Background: Health system inequities are major drivers of cancer outcomes in Latin America, where rapidly ageing populations intersect with fragmented access to specialized oncologic care. In high-grade serous ovarian cancer (HGSOC), older age and treatment within resource-limited health systems are associated with worse survival. Whether these associations reflect intrinsic tumour biology or are mediated by inequities in access to optimal care remains unclear. Global assessments have demonstrated variation in HGSOC outcomes by world region and Human Development Index, underscoring the role of health system capacity in shaping survival. Chile, with its segmented public–private health system, provides a natural setting to disentangle these effects. Methods: We conducted a retrospective cohort including 450 patients with HGSOC treated within the Chilean public or private health systems, with 20th years of follow up. The primary endpoint was overall survival (OS), defined as time from diagnosis to death from any cause. For independent prognostic factors we used Cox proportional hazards models integrating age (>65 vs ≤65 years), health system (public vs private), surgical strategy, FIGO stage, lactate dehydrogenase (LDH), and BRCA/HRD status. We evaluated whether age-related survival differences were attenuated after adjustment for health system and surgical strategy, conceptualized as proxies for access to specialized oncologic care. Attenuation was interpreted as consistent with mediation by access to care; however, formal causal mediation analyses were not performed. A propensity score model and inverse probability of treatment weighting (IPTW) were applied as sensitivity analyses. Results: Median OS was 48·2 months and median PFS was 13·8 months. In unadjusted analyses, OS differed significantly by age, stage, surgical strategy, LDH, BRCA/HRD status, and health system. In multivariable models, advanced stage, absence of primary cytoreductive surgery, elevated LDH, BRCA/HRD negativity, and treatment in the public health system were independently associated with worse OS, whereas age was not independently associated with OS after adjustment. IPTW analyses confirmed a robust association between primary cytoreductive surgery and improved OS (hazard ratio 0·29). The survival benefit of primary cytoreductive surgery was preserved across age groups. Conclusions: In this cohort, age-related survival differences in HGSOC were largely explained by inequities in access to optimal surgical care and comprehensive oncologic treatment rather than by chronological age or tumor biology. In segmented health systems such as those in Chile and much of Latin America, structural barriers to specialized care represent key determinants of survival.