1. What is PSA Doubling Time?

PSA doubling time (PSADT) is the time it takes for a man's PSA level to double. It's an important prognostic marker in prostate cancer management, particularly for monitoring disease progression and guiding treatment decisions.

2. How Does the Calculator Work?

The calculator uses the Sloan Kettering 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)

Explanation: The formula calculates the natural logarithm of the PSA ratio divided by the time interval, then determines how long it would take to double at that rate.

3. Clinical Importance

Details: PSADT is used to assess prostate cancer aggressiveness. Shorter doubling times (<3 months) may indicate more aggressive disease and higher risk of metastasis.

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 most reliable results.

5. Frequently Asked Questions (FAQ)

Q1: What is a normal PSA doubling time?
A: In prostate cancer, >10 months is generally favorable, 3-10 months is intermediate, and <3 months suggests aggressive disease.

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

Q3: Does this apply to post-treatment PSA?
A: Yes, PSADT after treatment (especially after radical prostatectomy) is a strong predictor of outcomes.

Q4: What factors can affect PSADT accuracy?
A: PSA variability, acute prostatitis, recent procedures (biopsy, cystoscopy), and hormonal fluctuations.

Q5: How does PSADT guide treatment decisions?
A: Short PSADT may prompt earlier intervention, while long PSADT may support continued active surveillance.