Calculator

Breast Cancer Foundation NZ Risk Calculator

Estimate an individual woman’s 5-year risk of breast cancer

The lifetime risk of female breast cancer in NZ is 1 in 9. Individual risk varies based on factors including personal history, ethnicity, family history, and lifestyle.

This NZ breast cancer risk calculator was developed using individual record data from a large national case-control study1,2. The relative risks for selected predictors (both biologically plausible and statistically important in the NZ dataset) were combined with baseline breast cancer incidence rates and non-breast cancer mortality rates to calculate individual probabilities of developing breast cancer within 5 years.

This model predicts risk in women aged 25-54. It is designed for use in unscreened asymptomatic women and should not be used for diagnostic purposes. Women with symptoms should be investigated according to best practice. Breast density is not incorporated into this model.

Women with a strong family history of breast or ovarian cancer should follow best practice guidelines for risk management and not rely on a risk predictor. This model is not recommended for women with a BRCA gene mutation. More detailed genetic and family history modelling (e.g. NZ Genetic Health Service), should be undertaken for these women.

A risk calculator for breast cancer can be used at the individual level to:

  • heighten the index of suspicion of doctors to promote earlier diagnosis and aid referral of patients for specialist surveillance
  • permit individual counselling for prevention, surveillance and management options, and improve compliance. Personal decisions can be based on absolute risk, not risk compared to other women
  • help manage anxiety about personal risk.
Low risk
Moderate risk
High risk
Very high risk
44%
of developing breast cancer in the next 5 years

References

  1. Paul, C., et al., Depot medroxyprogesterone (Depo-Provera) and risk of breast cancer. BMJ, 1989. 299: p. 759-62.
  2. Paul, C., et al., Oral contraceptives and breast cancer: a national study. British Medical Journal, 1986. 293: p. 723-726.
  3. Lawrenson, R., et al., Breast cancer inequities between Māori and non Māori women in Aotearoa/New Zealand. European journal of cancer care, 2016. 25(2): p. 225-230.
  4. Ministry of Health NZ, Cancer: New registrations 2009-2019, Ministry of Health NZ: Wellington, NZ.
  5. Teng, A.M., et al., Ethnic inequalities in cancer incidence and mortality: census-linked cohort studies with 87 million years of person-time follow-up. BMC cancer, 2016. 16(1): p. 1-14.
  6. Britt, K, Menarche, menopause, and breast cancer risk. Lancet Oncology www.thelancet.com/oncology Vol 13 November 2012. http://dx.doi.org/10.1016/S1470-2045(12)70456-4
  7. Wild CP, Weiderpass E, Stewart BW, editors (2020). World Cancer Report: Cancer Research for Cancer Prevention. Lyon, France: International Agency for Research on Cancer. Available from: http://publications.iarc.fr/586.
  8. Román M et al., Long-Term Risk of Breast Cancer after Diagnosis of Benign Breast Disease by Screening Mammography. Int. J. Environ. Res. Public Health 2022, 19, 2625. https://doi.org/10.3390/ijerph19052625.