1. What is PSA Doubling Time?

PSA doubling time (PSADT) is the time it takes for the prostate-specific antigen (PSA) level to double in value. It's an important prognostic marker in prostate cancer management, particularly for monitoring disease progression and treatment response.

2. How Does the Calculator Work?

The calculator uses the Memorial Sloan Kettering Cancer Center (MSKCC) formula:

Where:

• \( td \) — PSA doubling time (months)
• \( PSA1 \) — Initial PSA value (ng/mL)
• \( PSA2 \) — Current PSA value (ng/mL)
• \( t1 \) — Time of initial PSA measurement (months)
• \( t2 \) — Time of current PSA measurement (months)
• \( \ln \) — Natural logarithm function

Explanation: The formula calculates the exponential growth rate of PSA and determines how long it would take to double at that rate.

3. Importance of PSA Doubling Time

Details: PSADT helps assess prostate cancer aggressiveness. Shorter doubling times (<6 months) may indicate more aggressive disease and influence treatment decisions.

4. Using the Calculator

Tips: Enter PSA values in ng/mL and time points in months. Ensure current PSA is higher than initial PSA and current time is later than initial time.

5. Frequently Asked Questions (FAQ)

Q1: What is a clinically significant PSADT?
A: Generally, <3 months is very rapid, 3-6 months is rapid, 6-12 months is intermediate, and >12 months is slow.

Q2: How many PSA points are needed for accurate calculation?
A: While two points give an estimate, more measurements over time provide a more reliable trend.

Q3: Does PSADT apply to all prostate cancer patients?
A: It's most useful for monitoring biochemical recurrence after treatment or in active surveillance.

Q4: Can PSADT be negative?
A: Yes, if PSA decreases (PSA2 < PSA1), it indicates a negative doubling time (PSA halving time).

Q5: What factors can affect PSADT accuracy?
A: PSA variability, recent procedures, infections, or medications can temporarily affect PSA levels.