House value as an individual socioeconomic indicator for breast cancer survival and late-stage diagnosis: a population-based cohort study from Northern Ireland

Background: Socio-economic inequalities in breast cancer survival persist globally, including in the UK. Area-based deprivation measures may underestimate true socio-economic effects by assigning average levels to all individuals within an area. This study investigated associations between house value (individual-level socio-economic indicator) and area-based deprivation with breast cancer outcomes in Northern Ireland. Methods: Women diagnosed with breast cancer 2011 to 2021 were identified using the Northern Ireland Cancer Registry. House value was determined from Valuation and Lands Agency property valuation data, and area-based deprivation was determined from the Northern Ireland Multiple Deprivation Measure. The primary outcome was breast cancer-specific mortality. Secondary outcomes included stage at diagnosis. Cox regression models calculated adjusted hazard ratios (HR) and (95%CIs) for cancer-specific mortality by house value category and separately for deprivation, adjusting for confounders. Results: Among 12,766 women with breast cancer, associations were much more pronounced for house value than area-based deprivation. Women in the lowest house value category, compared to the highest value category, had a 60% increase in mortality (adjusted HR=1.60 95%CI 1.34, 1.92) and were more likely to be diagnosed with stage 4 disease (7.5% versus 4.1%; P<0.001). Women living in the most versus least deprived areas had a 26% increase in mortality (adjusted HR=1.26 95%CI 1.08, 1.47) and were more likely to be diagnosed with stage 4 disease (5.9% vs 5.0%; P =0.157). Conclusion: House value demonstrated stronger associations with breast cancer outcomes than area-level deprivation, suggesting it may serve as a more sensitive indicator for monitoring health inequalities in cancer.