1. What is PSA Doubling Time?

PSA doubling time (PSADT) is the time it takes for prostate-specific antigen levels to double in the blood. It's an important prognostic marker in prostate cancer management, helping assess disease aggressiveness and guide treatment decisions.

2. How Does the Calculator Work?

The calculator uses the PSA doubling time formula:

Where:

• \( td \) — PSA doubling time (months)
• \( PSA1 \) — Initial PSA measurement (ng/mL)
• \( PSA2 \) — Current PSA measurement (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 takes to double at that rate.

3. Clinical Significance

Details: Shorter PSADT (<3 months) suggests aggressive disease, while longer PSADT (>15 months) indicates slower progression. Used for monitoring after radical prostatectomy or radiation therapy.

4. Using the Calculator

Tips: Enter PSA values in ng/mL and time points in months. Ensure PSA2 > PSA1 and t2 > t1 for valid calculation. At least 3 PSA measurements over ≥6 months provide more reliable results.

5. Frequently Asked Questions (FAQ)

Q1: What is a concerning PSA doubling time?
A: Doubling times <3 months are concerning for aggressive disease, while >15 months typically indicate indolent progression.

Q2: How many PSA measurements are needed?
A: Minimum 2 measurements, but ≥3 measurements over ≥6 months provide more reliable estimates.

Q3: Does PSADT differ after different treatments?
A: Yes, expected PSADT varies post-surgery vs. radiation. Always interpret in clinical context.

Q4: Can PSADT be used for screening?
A: No, it's primarily used for monitoring known prostate cancer, not initial diagnosis.

Q5: What affects PSA doubling time accuracy?
A: PSA variability, recent procedures (biopsy, cystoscopy), infections, and certain medications can affect results.