Socioeconomic inequalities in stage-specific breast cancer incidence: a nationwide registry study of 1.1 million young women in Norway, 2000–2015

Authors

  • Cassia Bree Trewin Norwegian National Advisory Unit on Women’s Health, Oslo University Hospital, Oslo, Norway; Department of Registration, Cancer Registry of Norway, Oslo, Norway; Faculty of Medicine, University of Oslo, Oslo, Norway
  • Kirsti Vik Hjerkind Department of Registration, Cancer Registry of Norway, Oslo, Norway
  • Anna Louise Viktoria Johansson Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden; Cancer Registry of Norway, Oslo, Norway
  • Bjørn Heine Strand Department of Chronic Diseases and Ageing, Norwegian Institute of Public Health, Oslo, Norway; Department of Community Medicine, Institute of Health and Society, University of Oslo, Oslo, Norway
  • Cecilie Essholt Kiserud National Advisory Unit on Late Effects after Cancer Treatment, Oslo University Hospital, Oslo, Norway
  • Giske Ursin Cancer Registry of Norway, Oslo, Norway; Department of Nutrition, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway; Department of Preventative Medicine, University of Southern California, Los Angeles, CA, USA

DOI:

https://doi.org/10.1080/0284186X.2020.1753888

Abstract

Background

Women with high socioeconomic status (SES) have the highest incidence rates of breast cancer. We wanted to determine if high SES women only have higher rates of localized disease, or whether they also have higher rates of non-localized disease. To study this, we used data on a young population with universal health care, but not offered screening.

Material and methods

Using individually linked registry data, we compared stage-specific breast cancer incidence, by education level and income quintile, in a Norwegian cohort of 1,106,863 women aged 30–48 years during 2000–2015 (N = 7531 breast cancer cases). We calculated stage-specific age-standardized rates and incidence rate ratios and rate differences using Poisson models adjusted for age, period and immigration history.

Results

Incidence of localized and regional disease increased significantly with increasing education and income level. Incidence of distant stage disease did not vary significantly by education level but was significantly reduced in the four highest compared to the lowest income quintile. The age-standardized rates for tertiary versus compulsory educated women were: localized 28.2 vs 19.8, regional 50.8 vs 40.4 and distant 2.3 vs 2.6 per 100,000 person-years. The adjusted incidence rate ratios (tertiary versus compulsory) were: localized 1.40 (95% CI 1.25–1.56), regional 1.25 (1.15–1.35), distant 0.90 (0.64–1.26). The age-standardized rates for women in the highest versus lowest income quintile were: localized 28.9 vs 17.7, regional 52.8 vs 41.5 and distant 2.3 vs 3.2 per 100,000 person-years. The adjusted incidence rate ratios (highest versus lowest quintile) were: localized 1.63 (1.42–1.87), regional 1.27 (1.09–1.32), distant 0.64 (0.43–0.94).

Conclusion

Increased breast cancer rates among young high SES women is not just increased detection of small localized tumors, but also increased incidence of tumors with regional spread. The higher incidence of young high SES women is therefore real and not only because of excessive screening.

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Published

2020-04-22

How to Cite

Bree Trewin, C., Vik Hjerkind, K., Louise Viktoria Johansson, A., Heine Strand, B., Essholt Kiserud, C., & Ursin, G. (2020). Socioeconomic inequalities in stage-specific breast cancer incidence: a nationwide registry study of 1.1 million young women in Norway, 2000–2015. Acta Oncologica, 59(11), 1284–1290. https://doi.org/10.1080/0284186X.2020.1753888

Issue

Vol. 59 No. 11 (2020): Acta Oncologica

Section

Articles