What is the Tyrer-Cuzick model (IBIS tool) for breast cancer risk assessment?

Updated: Dec 16, 2019
  • Author: Jessica Katz, MD, PhD, FACP; Chief Editor: Marie Catherine Lee, MD, FACS  more...
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The Tyrer-Cuzick model, or IBIS tool, is used to calculate a person’s likelihood of carrying the BRCA1 or BRCA2 mutations. It estimates the likelihood of a woman developing breast cancer in 10 years and over the course of her lifetime. The tool is used to help inform a person’s decision-making about genetic counselling and testing. If the model predicts a 10% or greater chance that the woman has a mutation in BRCA1, BRCA2, or both, genetic counseling is advised. [53]

The tool estimates breast cancer risk on the basis of the following risk factors [53] :

  • Age
  • Body mass index
  • Age at menarche
  • Obstetric history
  • Age at menopause (if applicable)
  • History of a benign breast condition that increases breast cancer risk (hyperplasia, atypical hyperplasia, LCIS)
  • History of ovarian cancer
  • Use of hormone replacement therapy
  • Family history (including breast and ovarian cancer, Ashkenazi inheritance, genetic testing if done)

A comparison study of breast cancer risk models concluded that the Tyrer–Cuzick model is the most consistently accurate, whereas the Gail, Claus, and Ford models all significantly underestimate risk. [54] However, a study by Boughey et al found that the Tyrer-Cuzick model significantly overestimated the risk of breast cancer in women with atypical hyperplasia. [55]


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