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Breast Cancer Risk Calculator

Estimate your 5-year breast cancer risk with a simplified Gail model.

35–85 years

FactorEffect on risk
Age at first menstrual periodEarly menarche (< 12) raises risk by ~20 %
First-degree relatives with breast cancerOne first-degree relative roughly doubles risk
Atypical hyperplasia on biopsyAtypical hyperplasia nearly doubles risk
First live birthFirst birth ≥ 30 or nulliparity raises risk
Current ageRisk rises nearly linearly with age up to ~75 years

How it works

This calculator uses a simplified version of the Gail model (NCI Breast Cancer Risk Assessment Tool). It combines your risk factors into a relative risk and multiplies it by age-specific breast cancer incidence. A 5-year probability ≥ 1.66 % is considered elevated.

Frequently Asked Questions

What is the Gail model?+
The Gail model (Gail et al. 1989) estimates individual 5-year and lifetime breast cancer risk from several risk factors — age, menarche, first birth, family history, and prior biopsies. It is the basis of the NCI Breast Cancer Risk Assessment Tool.
When is my risk considered elevated?+
Guidelines (NCI, ASCO) define a 5-year risk ≥ 1.66 % as elevated. At that level you may be eligible for enhanced screening or risk-reducing medication.
Which risk factors are included?+
Current age, age at menarche, age at first live birth or nulliparity, number of breast biopsies (with or without atypical hyperplasia), and breast cancer in first-degree relatives (mother, sister, daughter).
Which factors are not included?+
The Gail model underestimates risk for BRCA1/BRCA2 carriers and women with male relatives or second-degree relatives affected. Breast density, lifestyle, and hormone therapy are not included either.
How accurate is this estimate?+
At a population level, the Gail model is well calibrated (Costantino 1999, AUC ≈ 0.58–0.65). Individual prediction accuracy remains modest — treat the result as a conversation starter, not a diagnosis.
What if my risk is elevated?+
If your 5-year risk is ≥ 1.66 %, ask your physician about enhanced screening (annual mammography ± MRI). At very high risk (e.g. ≥ 3 % over 5 years), preventive medication with tamoxifen or raloxifene may be discussed.

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Background

Breast Cancer Risk Calculator: How the Gail Model Works

9 min