For full clinical IBIS Tyrer-Cuzick calculation, use ibis-risk-calculator.magview.com. This module provides a risk category approximation based on key variables.
Tyrer-Cuzick (IBIS) Breast Cancer Risk
Multifactorial breast cancer risk model integrating family history, hormonal factors, BRCA probability, ADH/LCIS, and density. Endorsed by NICE NG101, ACMG, NCCN.
1st-Degree Relatives with Breast Cancer
2nd-Degree Relatives with Breast Cancer
BRCA Status
Atypical Ductal Hyperplasia (ADH) or ALH on Biopsy?
LCIS (Lobular Carcinoma In Situ)?
Mammographic Density (BI-RADS)
Ashkenazi Jewish Ancestry?
Guidelines & Evidence
Clinical Details
Section 1
When to Use
When to Use
Estimating 10-year and lifetime risk of breast cancer for surveillance and chemoprevention decisions.
Identifying women who should be offered enhanced surveillance (annual MRI) beyond standard mammography.
Triaging candidates for BRCA1/2 and expanded hereditary breast cancer gene panel testing.
Endorsed by NICE (UK), ACMG, NCCN, and ASBrS as a comprehensive multifactorial risk model.
What Makes IBIS Different
Tyrer-Cuzick is the most comprehensive individual risk model — integrating family history (both sides), hormonal factors, BRCA carrier probability, density, and atypical hyperplasia in a single Bayesian framework. It consistently outperforms Gail model for women with strong family history.
Section 2
Formula & Logic
Input Variables
Current age; menopausal status; age at menarche; age at first live birth
HRT use; OCP use; current BMI (post-menopausal women)
Maternal AND paternal family history (age at diagnosis, type of cancer, bilateral vs unilateral)
Personal history of LCIS, ADH, ALH (atypical hyperplasia — major risk multiplier)
Ashkenazi Jewish ancestry (BRCA prior)
Known BRCA1/2 status (if tested)
Mammographic breast density (BI-RADS / Volpara)
Risk Output and Thresholds
10-Year Risk
Category
Surveillance Recommendation (NICE NG101)
< 3%
Population (average) risk
NHS screening programme (mammography from 50)
3–8%
Moderate risk
Annual mammography from 40; discuss chemoprevention (tamoxifen/raloxifene)
> 8% OR Lifetime > 30%
High risk
Annual MRI + mammography from 30–40; BRCA testing; chemoprevention
Lifetime > 60% OR BRCA ≥ 30% probability
Very High / BRCA-equivalent risk
Risk-reducing surgery discussion; intensive MRI surveillance
Section 3
Pearls/Pitfalls
Key Pearls
Atypical hyperplasia (ADH/ALH) is a ~4× risk multiplier — amplified further by family history. Women with both features are at very high risk.
IBIS version 8 incorporates SNP polygenic risk score option — not yet standard in most clinical workflows.
Output includes estimated BRCA1 and BRCA2 carrier probability — use this to guide genetic testing decisions.
IBIS tool does NOT account for endogenous oestrogen level — for post-menopausal women on aromatase inhibitors, risk may be further modified.
Section 4
Next Steps
Clinical Actions
01
Moderate risk (3–8%): Annual mammography from 40; pharmacological chemoprevention discussion (tamoxifen 5yr for pre-menopausal; raloxifene/anastrozole for post-menopausal).
02
High risk (> 8% or lifetime > 30%): Annual MRI + mammography protocol starting age 30–40; refer to genetics clinic; BRCA panel testing.
03
Very high risk / BRCA-equivalent: Multidisciplinary discussion for risk-reducing mastectomy vs surveillance; BSO consideration for ovarian risk.
04
All risk levels: Lifestyle counselling (weight, alcohol, exercise); optimise HRT duration and form.
Section 5
Evidence Appraisal
Primary Reference
A breast cancer prediction model incorporating familial and personal risk factors
Tyrer J et al. • Statistics in Medicine. 2004;23(7): 1111–1130
Section 6
Literature
Development
Developed by Jonathan Tyrer and Jack Cuzick at the International Agency for Research on Cancer (IARC) and Queen Mary University of London, published in Statistics in Medicine in 2004. The model was designed specifically to overcome the limitations of the Gail model in women with significant family history, incorporating BRCA carrier probability as a latent variable in a Bayesian framework.
IBIS (International Breast Cancer Intervention Study) Tool
The Tyrer-Cuzick model is implemented as the IBIS Breast Cancer Risk Evaluation Tool, available freely online and integrated into clinical risk assessment pathways. It was validated in multiple prospective cohorts including the Prospective Family Study Cohort (ProF-SC) and consistently demonstrates superior calibration to Gail in high-risk populations. NICE NG101 in the UK mandates its use for risk stratification in familial breast cancer clinics.
