Impact of Marginalization Dimensions on Survival Disparities in Epithelial Ovarian Cancer: An Ontario...

Objectives: We aimed to examine associations between social marginalization, defined by the Ontario Marginalization Index ("ON-Marg"), and overall survival (OS) in epithelial ovarian cancer (EOC). Methods: This was a population-based retrospective cohort study using linked administrative data in Ontario, Canada, including adults ≥ 18 years diagnosed with stage II-IV EOC (2010-2022). ON-Marg dimensions included Material Resources (economic disadvantage), Households and Dwellings (housing type/density), Age and Labour Force (workforce participation), and Racialized and Newcomer Populations (recent immigrants/visible minorities), and were categorized into quintiles (Q1 least marginalized, Q5 most marginalized). The primary outcome was OS. Multivariable Cox models estimated adjusted hazard ratios (aHR) for each ON-Marg dimension. Wald χ² statistics identified the dimension most strongly associated with OS. Results: Material Resources was most strongly associated with OS. Compared with Q1 (least marginalized), higher mortality was observed in Q3 (aHR 1.10; 95%CI 1.02-1.19), Q4 (aHR 1.13, 95%CI 1.05-1.22), and Q5 (aHR 1.25, 95%CI 1.15-1.35). Greater marginalization in the Racialized and Newcomer Populations dimension was associated with improved OS (Q5 aHR 0.87, 95%CI 0.80-0.94). The association between Material Resources and OS persisted in patients undergoing cytoreductive surgery with chemotherapy, but not among those receiving chemotherapy alone or no treatment. Conclusions: Material Resources is an independent predictor of survival in EOC within a universal, publicly funded healthcare system, with greatest impact among patients undergoing multimodal oncologic care. Residence in highly racialized or newcomer communities was associated with improved survival. Material marginalization is highlighted as a key driver of inequity, supporting targeted system-level interventions to address financial and logistical barriers to care.