This calculator provides an estimated probability of breast cancer risk based on several well-established risk factors. This is not a diagnostic tool and should not replace professional medical advice.
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Understanding Breast Cancer Risk Factors and the Calculator
Breast cancer is a complex disease, and its development is influenced by a combination of genetic, environmental, and lifestyle factors. While not all factors can be controlled, understanding personal risk can empower individuals to make informed decisions about screening and preventive measures. This calculator aims to provide an estimated risk based on common, scientifically supported risk factors. It's important to remember that this is a risk assessment tool, not a diagnostic tool.
How the Calculator Works (Simplified Model)
This calculator uses a simplified approach inspired by models like the Gail Model (also known as the Breast Cancer Risk Assessment Tool). These models assign relative weights or points to various risk factors. Each factor contributes to an overall risk score, which is then translated into a probability percentage over a specific time frame (commonly 5-year and lifetime risk).
The calculation involves several steps:
Age: Risk increases significantly with age.
Reproductive History:
Starting menstruation at a younger age (early menarche) increases risk.
Starting menopause at a later age increases risk.
Having children at an older age at first birth increases risk.
Having many full-term pregnancies can be protective, but the timing of the first birth is also a factor.
Personal and Family History:
A personal history of breast cancer dramatically increases the risk of a new or recurrent cancer.
A family history of breast cancer, especially in first-degree relatives (mother, sister, daughter), indicates a higher genetic predisposition.
Hormone Use: Prolonged use of post-menopausal hormone therapy (HRT) has been linked to increased risk.
Breast Density: Dense breasts (more glandular and fibrous tissue compared to fatty tissue) are associated with a higher risk.
The calculator synthesizes these inputs. For instance, a woman who started menstruating early, went through menopause late, had her first child after 30, has dense breasts, and has a family history of breast cancer will likely receive a higher risk score than a woman with opposing factors.
Interpreting the Results
The output typically provides a percentage representing your estimated risk of developing invasive breast cancer over a defined period (e.g., the next 5 years and/or over your lifetime). For example:
"Your estimated 5-year risk is 1.2%." This means that based on the inputs, approximately 1.2 out of 100 women with similar risk factors are expected to develop invasive breast cancer in the next 5 years.
"Your estimated lifetime risk is 15%." This suggests that approximately 15 out of 100 women with similar risk factors are expected to develop invasive breast cancer at some point in their lives.
Important Considerations:
This is an estimate: Individual risk can vary. The models are based on population data and may not perfectly reflect your unique biological makeup.
Not a substitute for medical advice: Always discuss your personal risk factors, screening schedules, and any concerns with your healthcare provider. They can provide personalized recommendations based on your complete medical history and physical examination.
Screening Guidelines: Your doctor will use this information, along with other clinical factors, to recommend appropriate breast cancer screening (e.g., mammograms, MRIs) tailored to your risk level.
By using this calculator and consulting with your doctor, you can gain a better understanding of your breast cancer risk and take proactive steps towards breast health.
function calculateBreastCancerRisk() {
var age = parseFloat(document.getElementById("age").value);
var menarcheAge = parseFloat(document.getElementById("menarcheAge").value);
var menopauseAge = parseFloat(document.getElementById("menopauseAge").value);
var numChildren = parseFloat(document.getElementById("numChildren").value);
var ageAtFirstBirth = parseFloat(document.getElementById("ageAtFirstBirth").value);
var historyBreastCancer = parseInt(document.getElementById("historyBreastCancer").value);
var familyHistory = parseInt(document.getElementById("familyHistory").value);
var hormoneTherapy = parseInt(document.getElementById("hormoneTherapy").value);
var denseBreasts = parseInt(document.getElementById("denseBreasts").value);
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = ";
// Input validation
if (isNaN(age) || age 90) {
resultDiv.innerHTML = 'Please enter a valid age between 20 and 90.';
return;
}
if (isNaN(menarcheAge) || menarcheAge 16) {
resultDiv.innerHTML = 'Please enter a valid age at first menstruation between 8 and 16.';
return;
}
if (isNaN(menopauseAge) || menopauseAge 60) {
// Allow 0 for not menopausal, but handle the logic later
if (menopauseAge !== 0) {
resultDiv.innerHTML = 'Please enter a valid age at menopause between 40 and 60, or 0 if not applicable.';
return;
}
}
if (isNaN(numChildren) || numChildren 15) {
resultDiv.innerHTML = 'Please enter a valid number of children (0-15).';
return;
}
if (numChildren > 0 && (isNaN(ageAtFirstBirth) || ageAtFirstBirth 50)) {
resultDiv.innerHTML = 'Please enter a valid age at first birth between 15 and 50 if you have children.';
return;
}
if (numChildren === 0 && ageAtFirstBirth !== 0) {
resultDiv.innerHTML = 'If you have no children, age at first birth should be 0.';
return;
}
// Simplified risk score calculation – NOT a direct implementation of Gail Model
// This is a conceptual representation for demonstration purposes.
// Real Gail model calculation is complex and requires specific coefficients.
var riskScore = 0;
// Age component (simplified exponential increase)
riskScore += Math.max(0, age – 40) * 0.05; // Add risk for age over 40
// Reproductive factors (Inverse relationship for children, younger menarche/later menopause increase risk)
if (menopauseAge === 0) { // Pre-menopausal
riskScore += (14 – menarcheAge) * 0.1; // Younger menarche adds risk
} else { // Post-menopausal
riskScore += (14 – menarcheAge) * 0.1; // Younger menarche adds risk
riskScore += (menopauseAge – 50) * 0.1; // Later menopause adds risk
}
if (numChildren > 0) {
riskScore -= (numChildren – 1) * 0.05; // Having more children reduces risk
if (ageAtFirstBirth > 0) {
riskScore += Math.max(0, ageAtFirstBirth – 24) * 0.05; // Later first birth adds risk
}
}
// History factors
riskScore += historyBreastCancer * 0.5; // Personal history is a significant factor
riskScore += familyHistory * 0.3; // Family history adds risk
// Other factors
riskScore += hormoneTherapy * 0.2;
riskScore += denseBreasts * 0.2;
// Convert score to a probability percentage (highly simplified and illustrative)
// This conversion is conceptual. Actual models use complex formulas and lookup tables.
var estimatedRiskPercentage = Math.min(50, Math.max(0.1, riskScore * 5)); // Cap at 50% for simplicity
// Display results
resultDiv.innerHTML = 'Your estimated risk is approximately ' + estimatedRiskPercentage.toFixed(2) + '% (Illustrative)';
}