Ethnic disparities in breast cancer survival in New Zealand: which factors contribute?

Abstract

BackgroundNew Zealand has major ethnic disparities in breast cancer survival with Māori (indigenous people) and Pacific women (immigrants or descended from immigrants from Pacific Islands) faring much worse than other ethnic groups. This paper identified underlying factors and assessed their relative contribution to this risk differential.MethodsThis study involved all women who were diagnosed with primary invasive breast cancer in two health regions, covering about 40% of the national population, between January 2000 and June 2014. Māori and Pacific patients were compared with other ethnic groups in terms of demographics, mode of diagnosis, disease factors and treatment factors. Cox regression modelling was performed with stepwise adjustments, and hazards of excess mortality from breast cancer for Māori and Pacific patients were assessed.ResultsOf the 13,657 patients who were included in this analysis, 1281 (9.4%) were Māori, and 897 (6.6%) were Pacific women. Compared to other ethnic groups, they were younger, more likely to reside in deprived neighbourhoods and to have co-morbidities, and less likely to be diagnosed through screening and with early stage cancer, to be treated in a private care facility, to receive timely cancer treatment, and to receive breast conserving surgery. They had a higher risk of excess mortality from breast cancer (age and year of diagnosis adjusted hazard ratio: 1.76; 95% CI: 1.51–2.04 for Māori and 1.97; 95% CI: 1.67–2.32 for Pacific women), of which 75% and 99% respectively were explained by baseline differences. The most important contributor was late stage at diagnosis. Other contributors included neighbourhood deprivation, mode of diagnosis, type of health care facility where primary cancer treatment was undertaken and type of loco-regional therapy.ConclusionsLate diagnosis, deprivation and differential access to and quality of cancer care services were the key contributors to ethnic disparities in breast cancer survival in New Zealand. Our findings underscore the need for a greater equity focus along the breast cancer care pathway, with an emphasis on improving access to early diagnosis for Māori and Pacific women.Electronic supplementary materialThe online version of this article (10.1186/s12885-017-3797-0) contains supplementary material, which is available to authorized users.

Status epilepticus in Auckland, New Zealand: Incidence, etiology, and outcomes

“…We have identified an increased risk of SE in Māori and Pacific Islanders; the reason for this difference requires further investigation. Similar ethnic disparity in health outcome has previously been described in New Zealand, [28][29][30] the cause of which is likely multifactorial, including the effects of colonization and lack of socioeconomic opportunity. The incidence of prolonged febrile seizures and convulsive SE in London was higher in those with socioeconomic deprivation.…”

Development and validation of a new predictive model for breast cancer survival in New Zealand and comparison to the Nottingham prognostic index

“…Maori and Pacific women in NZ with breast cancer have a worse prognosis and higher mortality [ 23 , 54 ], however, the current results show that Maori or Pacific ethnicity have no independent predictive value on 10-year survival, once detailed clinical and pathological factors are taken into account. This suggests the ethnicity factors are mediated through these clinical and pathological variables, and agrees with other detailed analyses [ 16 ]. Thus, while at the population level different approaches may be needed to overcome the disparities in outcomes of the different ethnic groups, at a clinical level the assessment of prognosis in each women may not be affected by her ethnic group.…”

“…We used the data collected prospectively through the two largest and longest-established population-based regional breast cancer registries in NZ, in the Auckland and Waikato regions. These two regional registries are linked to include over 40% of all patients with breast cancer in NZ, and are representative of NZ women in terms of socioeconomic, demographic and ethnic background [ 16 , 21 ]. The registries are linked to national mortality data and to the legally-mandated national cancer registry [ 22 ] and to other hospital discharge data to assess co-morbidity [ 22 ]; comparisons show that the registries are very complete (over 95%) [ 22 ].…”

“…These models use accepted clinical and pathological indicators, such as tumour size, nodal involvement, and receptor status. In addition to these factors, studies in NZ show that there are significant differences in breast cancer outcomes by social deprivation, rural residence, comorbidity, type of health care [ 16 – 18 ]. There are important differences by ethnicity, with Maori and Pacific women being at greater risks of death and recurrence than European NZ women, and these ethnic differences are complex and related to both clinic-pathological and demographic factors [ 16 , 18 – 20 ].…”

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“…Māori presenting with early stage disease are younger than non-Māori, and more likely to have COPD, be a current smoker, have an FEV1 less than 50% and have small cell histology. Māori generally have lower socioeconomic status which is associated with poor surviva [19,20]. After adjustment for these factors it appears that Māori are not less likely to receive curative treatment (odds ratio 0.80, 95% CI 0.46-1.38) or surgery (odds ratio 1.03, 95% CI: 0.53-2.00).…”