Socioeconomic and geographic disparities of breast cancer incidence according to stage at diagnosis in France.

PURPOSE: Low socioeconomic background (SB) has been associated with lower breast cancer (BC) incidence and higher BC mortality. One explanation of this paradox is the higher frequency of advanced BC observed in deprived women. However, it is still unclear if SB affects similarly BC incidence. This study investigated the link between SB and early/advanced BC incidence from Loire-Atlantique/Vendee Cancer registry data (France). MATERIALS AND METHODS: Fourteen thousand three hundred fifty three women living in the geographic area covered by the registry and diagnosed with a primary BC in 2008-2015 were included. SB was approached by a combination of two ecological indexes (French European Deprivation Index and urban/rural residence place). Mixed effects logistic and Poisson regressions were used, respectively, to estimate the odds of advanced (stage ≥ II) BC and the ratio of incidence rates of early (stage 0-I) and advanced BC according to SB, overall and by age group (< 50, 50-74, ≥ 75). RESULTS: Compared to women living in affluent-urban areas, women living in deprived-urban and deprived-rural areas had a higher proportion of advanced BC [respectively, OR = 1.11 (1.01-1.22), OR = 1.60 (1.25-2.06)] and lower overall (from - 6 to - 15%) and early (from - 9 to - 31%) BC incidences rates Advanced BC incidence rates were not influenced by SB. These patterns were similar in women under 75 years, especially in women living in deprived-rural areas. In the elderly, no association between SB and BC frequency/incidence rates by stage was found. CONCLUSION: Although advanced BC was more frequent in women living in deprived and rural areas, SB did not influence advanced BC incidence. Therefore, differences observed in overall BC incidence according to SB were only due to higher incidence of early BC in affluent and urban areas. Future research should confirm these results in other French areas.

Is survival rate lower after breast cancer in deprived women according to disease stage?

BACKGROUND: Socioeconomic deprivation has been associated with lower breast cancer (BC) survival, but the influence of stage at diagnosis on this association merits further study. Our aim was to investigate this association using the Loire-Atlantique/Vendee Cancer Registry (France). METHODS: Twelve-thousand seven-hundred thirty-eight women living in the area covered by the registry and diagnosed with invasive breast carcinoma between 2008 and 2015 were included in the study. They were censored at maximal 6 years. Deprivation was measured by the French European Deprivation Index. Excess hazard and net survival were estimated for deprivation level, stage and age at diagnosis using a flexible excess mortality hazard model. RESULTS: After adjustment by stage, women living in the most deprived areas had a borderline non-significant higher excess mortality hazard (+25% (95% CI: -3%; +62%)) compared to those living in the least deprived areas. Stage-adjusted 5-year net survival differed significantly between these two subgroups (respectively, 88.2% (95% CI:85.2%-90.5%) and 92.5% (95% CI:90.6%-93.9%)). CONCLUSION: BC survival remained lower in deprived areas in France, despite universal access to cancer care. Intensification of prevention measures could help to reduce advanced BC, responsible for the majority of deaths from BC. A better understanding of remaining social disparities is crucial to implement specific interventions.

Using ecological socioeconomic position (SEP) measures to deal with sample bias introduced by incomplete individual-level measures: inequalities in breast cancer stage at diagnosis as an example.

BACKGROUND: When studying the influence of socioeconomic position (SEP) on health from data where individual-level SEP measures may be missing, ecological measures of SEP may prove helpful. In this paper, we illustrate the best use of ecological-level measures of SEP to deal with incomplete individual level data. To do this we have taken the example of a study examining the relationship between SEP and breast cancer (BC) stage at diagnosis. METHODS: Using population based-registry data, all women over 18 years newly diagnosed with a primary BC in 2007 were included. We compared the association between advanced stage at diagnosis and individual SEP containing missing data with an ecological level SEP measure without missing data. We used three modelling strategies, 1/ based on patients with complete data for individual-SEP (n = 1218), or 2/ on all patients (n = 1644) using an ecological-level SEP as proxy for individual SEP and 3/ individual-SEP after imputation of missing data using an ecological-level SEP. RESULTS: The results obtained from these models demonstrate that selection bias was introduced in the sample where only patients with complete individual SEP were included. This bias is redressed by using ecological-level SEP to impute missing data for individual SEP on all patients. Such a strategy helps to avoid an ecological bias due to the use of aggregated data to infer to individual level. CONCLUSION: When individual data are incomplete, we demonstrate the usefulness of an ecological index to assess and redress potential selection bias by using it to impute missing individual SEP.

Are disparities of waiting times for breast cancer care related to socio-economic factors? A regional population-based study (France).

The increasing number of breast cancer cases may induce longer waiting times (WT), which can be a source of anxiety for patients and may play a role in survival. The aim of this study was to examine the factors, in particular socio-economic factors, related to treatment delays. Using French Cancer Registry databases and self-administered questionnaires, we included 1,152 women with invasive non-metastatic breast cancer diagnosed in 2007. Poisson regression analysis was used to identify WTs' influencing factors. For 973 women who had a malignant tissue sampling, the median of overall WT between the first imaging procedure and the first treatment was 44 days (9 days for pathological diagnostic WT and 31 days for treatment WT). The medical factors mostly explained inequalities in WTs. Socio-economic and behavioral factors had a limited impact on WTs except for social support which appeared to be a key point. Better identifying the factors associated with increase in WTs will make it possible to develop further interventional or prospective studies to confirm their causal role in delay and at last reduce disparities in breast cancer management.

Socioeconomic Deprivation and Invasive Breast Cancer Incidence by Stage at Diagnosis: A Possible Explanation to the Breast Cancer Social Paradox.

In this study, we assessed the influence of area-based socioeconomic deprivation on the incidence of invasive breast cancer (BC) in France, according to stage at diagnosis. All women from six mainland French departments, aged 15+ years, and diagnosed with a primary invasive breast carcinoma between 2008 and 2015 were included (n = 33,298). Area-based socioeconomic deprivation was determined using the French version of the European Deprivation Index. Age-standardized incidence rates (ASIR) by socioeconomic deprivation and stage at diagnosis were compared estimating incidence rate ratios (IRRs) adjusted for age at diagnosis and rurality of residence. Compared to the most affluent areas, significantly lower IRRs were found in the most deprived areas for all-stages (0.85, 95% CI 0.81-0.89), stage I (0.77, 95% CI 0.72-0.82), and stage II (0.84, 95% CI 0.78-0.90). On the contrary, for stages III-IV, significantly higher IRRs (1.18, 95% CI 1.08-1.29) were found in the most deprived areas. These findings provide a possible explanation to similar or higher mortality rates, despite overall lower incidence rates, observed in women living in more deprived areas when compared to their affluent counterparts. Socioeconomic inequalities in access to healthcare services, including screening, could be plausible explanations for this phenomenon, underlying the need for further research.