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

BackgroundSocio-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. MethodsWomen 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. ResultsAmong 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). ConclusionHouse 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. What is already knownLower socioeconomic status is associated with worse breast cancer survival in the UK and internationally. Area-based measures of deprivation are widely used in epidemiological research but have recognised limitations. What this study addsWe observed socio-economic gradients for both late-stage at diagnosis and breast cancer survival for both house value and area-deprivation. However, associations were stronger for house value and effects persisted after adjustment for area deprivation. How this might affect research, policy and practiceOur findings establish that publicly available property valuations provide a feasible and sensitive measure for monitoring socioeconomic health inequalities at the population level