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Ethnic differences in breast cancer survival in New Zealand: contributions of differences in screening, treatment, tumor biology, demographics and comorbidities

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Abstract

Purpose

We investigated the breast cancer survival disparity between Indigenous Māori and non-Indigenous European women in New Zealand, and quantified the relative contributions of patient, tumor and healthcare system factors toward this disparity.

Methods

All women diagnosed with breast cancer in Waikato, New Zealand, during 1999–2012 were identified from the Waikato Breast Cancer Register. Cancer-specific survivals were compared using Kaplan–Meier survival curves, while contributions of different factors toward the survival disparity were quantified with serial Cox proportional hazard modeling.

Results

Of the 2,679 women included in this study, 2,260 (84.4 %) were NZ European and 419 (15.6 %) were Māori. Compared with NZ European women, Māori women had a significantly higher age-adjusted cancer-specific mortality (HR 2.02, 95 % CI 1.59–2.58) with significantly lower 5-year (86.8 vs. 76.1 %, p < 0.001) and 10-year (79.9 vs. 66.9 %, p < 0.001 %) crude cancer-specific survivals. Stage at diagnosis made the greatest contribution (approximately 25–40 %), while screening, treatment and patient factors (i.e., comorbidity, obesity and smoking) contributed by approximately 15 % each toward the survival disparity. The final model accounted for almost all of the cancer survival disparity (HR 1.07, 95 % CI 0.80–1.44).

Conclusions

Māori women experience an age-adjusted risk of death from breast cancer, which is more than twice that for NZ European women. Equity-focussed improvements in health care, including increasing mammographic screening coverage and providing equitable quality and timely cancer care, may improve the survival disparity between Māori and NZ European women.

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Acknowledgments

We acknowledge funding support received from the Waikato Breast Cancer Trust, Waikato Bay of Plenty Division of the Cancer Society of New Zealand, New Zealand Breast Cancer Foundation, Lion Foundation, Grassroots Trust and WEL energy trust for the WBCR.

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Authors and Affiliations

  1. Waikato Clinical School, University of Auckland, Hamilton, New Zealand

    Sanjeewa Seneviratne, Ian Campbell & Ross Lawrenson

  2. Māori Health Services, Waikato District Health Board, Hamilton, New Zealand

    Nina Scott

  3. Waikato Breast Cancer Trust, Hamilton, New Zealand

    Rachel Shirley & Tamati Peni

  4. Breast Cancer Research Office, Waikato Hospital, PO Box 934, Hamilton, 3240, New Zealand

    Sanjeewa Seneviratne

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  1. Sanjeewa Seneviratne
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  2. Ian Campbell
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Correspondence to Sanjeewa Seneviratne.

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All authors declare that there are no conflicts of interest.

Ethics approval

Ethical approval for this study was obtained from the New Zealand Northern ‘A’ Ethics Committee (Ref. No. 12/NTA/42).

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Seneviratne, S., Campbell, I., Scott, N. et al. Ethnic differences in breast cancer survival in New Zealand: contributions of differences in screening, treatment, tumor biology, demographics and comorbidities. Cancer Causes Control 26, 1813–1824 (2015). https://doi.org/10.1007/s10552-015-0674-5

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  • DOI: https://doi.org/10.1007/s10552-015-0674-5

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