First-Time Exploration Into Breast Cancer Incidence And Mortality Across Small-Areas In Cyprus: Spatial Patterning And Associations With Rurality Indicators
METHODS: Standardised Mortality and Incidence Ratios (SMRs/SIRs) across 370 communities were calculated based on latest available registry data for period 2004-2011 and 2003-2008 respectively to ensure sufficient numbers. Bayesian hierarchical Poisson models with spatially unstructured and/or structured random effects were used to smooth maps and investigate the association with population density (rurality), population potential (remoteness from major population centers) and percentage of retired population.
RESULTS: SMRs (range 0-6) and SIRs (range 0-4) were unreliable at such a small level of aggregation (median population 129, IQR: 47-416, 10% of areas >1500). Nevertheless, up to two-fold differences remained across smoothed maps, with as much as 80% of the variation explained locally. Mortality and incidence demonstrated a similar geographic pattern with higher rates in and around metropolitan areas and lower rates in rural and mountainous areas. Population density (1.13 95%CI=1.04-1.23, per SD increase) and population potential (1.09 95%CI=1.01-1.19) were both significantly associated with increased mortality rates. Similar associations were observed with incidence rates which were also inversely associated with the percentage of retired population (0.92, 95%CI=0.84-0.99). Interestingly, more than three-fold differences were observed in Mortality-to-Incidence ratios, suggesting differences in survival and/or registration quality.
CONCLUSIONS: Even on a small island like Cyprus there is substantial small-area variation in breast cancer mortality and incidence rates, more likely to suggest urban-rural differences in reproduction-related factors, even though the influence of other lifestyle and environmental factors cannot be ruled out.