1. What is Patient Year Exposure?

Definition: Patient Year Exposure (PY) is a measure of the total time at risk for a group of patients, calculated by multiplying the number of patients by the time period.

Purpose: It helps researchers quantify drug exposure or risk time in clinical studies, particularly important in breast cancer research.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( PY \) — Patient years (person-years)
• \( N \) — Number of patients (dimensionless)
• \( T \) — Time period (years)

Explanation: The number of patients is multiplied by the time period to get the total patient-years of exposure.

3. Importance in Breast Cancer Research

Details: Patient-year exposure is crucial for calculating incidence rates, drug safety profiles, and treatment effectiveness over time in breast cancer studies.

4. Using the Calculator

Tips: Enter the number of patients and the time period in years. Both values must be > 0. The result shows the total patient-year exposure.

5. Frequently Asked Questions (FAQ)

Q1: Why use patient-years instead of just number of patients?
A: Patient-years account for both the number of patients and the duration of exposure, giving a more accurate measure of total risk time.

Q2: Can I use months instead of years?
A: Yes, but convert months to years (divide by 12) before entering the value for accurate calculations.

Q3: How is this used in breast cancer research?
A: It helps calculate incidence rates (cases per 1000 patient-years) and assess long-term treatment effects.

Q4: What if patients have different follow-up times?
A: For varying follow-up periods, calculate PY for each patient separately and sum them.

Q5: How precise should the time period be?
A: For clinical studies, time is often measured precisely (e.g., 2.5 years for 30 months).