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, helping assess disease aggressiveness and guide treatment decisions.

2. How Does the Calculator Work?

The calculator uses the following formula:

Where:

• \( T_d \) — PSA doubling time (months)
• \( PSA_1 \) — Initial PSA value (ng/mL)
• \( PSA_2 \) — Final PSA value (ng/mL)
• \( t_1 \) — Time of initial PSA measurement (months)
• \( t_2 \) — Time of final PSA measurement (months)
• \( \ln \) — Natural logarithm function

Explanation: The formula calculates the time required for PSA to double based on the rate of change between two measurements.

3. Clinical Significance

Details: Shorter PSADT (<3 months) suggests aggressive disease, while longer PSADT (>12 months) indicates slower progression. It's particularly useful in monitoring patients on active surveillance or after treatment.

4. Using the Calculator

Tips: Enter PSA values in ng/mL and time points in months. Ensure PSA values are >0 and t2 > t1. For best accuracy, use PSA values measured with the same assay method.

5. Frequently Asked Questions (FAQ)

Q1: What is considered a significant change in PSADT?
A: A PSADT shortening to <12 months often triggers clinical concern, while <6 months may indicate need for treatment change.

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

Q3: Does PSADT apply to all prostate cancer patients?
A: It's most useful for monitoring biochemical recurrence or active surveillance, less so for advanced metastatic disease.

Q4: What affects PSADT accuracy?
A: PSA bounces after radiation, lab variability, and concurrent conditions like prostatitis can affect accuracy.

Q5: How does PSADT compare to PSA velocity?
A: PSADT may be more consistent than velocity, especially at very low or very high PSA levels.