Impact of mammographic screening on ethnic and socioeconomic inequities in breast cancer stage at diagnosis and survival in New Zealand: a cohort study.

Sanjeewa Seneviratne,Ian Campbell,Ross Lawrenson,Nina Scott,Rachel Shirley

doi:10.1186/s12889-015-1383-4

Abstract

BackgroundIndigenous Māori women experience a 60% higher breast cancer mortality rate compared with European women in New Zealand. We explored the impact of differences in rates of screen detected breast cancer on inequities in cancer stage at diagnosis and survival between Māori and NZ European women.MethodsAll primary breast cancers diagnosed in screening age women (as defined by the New Zealand National Breast Cancer Screening Programme) during 1999–2012 in the Waikato area (n = 1846) were identified from the Waikato Breast Cancer Register and the National Screening Database. Stage at diagnosis and survival were compared for screen detected (n = 1106) and non-screen detected (n = 740) breast cancer by ethnicity and socioeconomic status.ResultsIndigenous Māori women were significantly more likely to be diagnosed with more advanced cancer compared with NZ European women (OR = 1.51), and approximately a half of this difference was explained by lower rate of screen detected cancer for Māori women. For non-screen detected cancer, Māori had significantly lower 10-year breast cancer survival compared with NZ European (46.5% vs. 73.2%) as did most deprived compared with most affluent socioeconomic quintiles (64.8% vs. 81.1%). No significant survival differences were observed for screen detected cancer by ethnicity or socioeconomic deprivation.ConclusionsThe lower rate of screen detected breast cancer appears to be a key contributor towards the higher rate of advanced cancer at diagnosis and lower breast cancer survival for Māori compared with NZ European women. Among women with screen-detected breast cancer, Māori women do just as well as NZ European women, demonstrating the success of breast screening for Māori women who are able to access screening. Increasing breast cancer screening rates has the potential to improve survival for Māori women and reduce breast cancer survival inequity between Māori and NZ European women.

Highlights

Indigenous Māori women experience a 60% higher breast cancer mortality rate compared with European women in New Zealand
This study included a total of 1846 screening age women (1548 invasive and 298 in-situ) with newly diagnosed first primary breast cancer over the study period
We found that patterns of inequities by socioeconomic deprivation were similar to those found between Māori and NZ European women

Summary

Introduction

Indigenous Māori women experience a 60% higher breast cancer mortality rate compared with European women in New Zealand. The burden of breast cancer has an unequal ethnic distribution in New Zealand as Indigenous Māori women have a higher incidence and a lower survival rate compared with NZ European women [2]. BreastScreen Aotearoa (BSA) is the New Zealand National Breast Screening Programme, a free mammographic breast screening service available for all ‘screening age’ women. Since it was established in 1999, the BSA has provided free biennial mammographic screening for all women aged between 50 to 64 years and this age range was extended to include women aged 45 to 49 and 65 to 69 years in July 2004

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