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:

• \( td \) — 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 takes to double at that rate.

3. Clinical Importance of PSA Doubling Time

Details: PSADT is used to:

• Assess prostate cancer aggressiveness
• Predict risk of metastasis
• Guide decisions about active surveillance vs. treatment
• Monitor treatment effectiveness

4. Using the Calculator

Tips:

• Enter PSA values in ng/mL
• Time values should be in months since a reference date
• Ensure PSA2 is more recent than PSA1
• For best results, use PSA values measured with the same assay

5. Frequently Asked Questions (FAQ)

Q1: What is a significant PSADT?
A: Generally, PSADT <3 months indicates aggressive disease, 3-12 months intermediate, and >12 months less aggressive.

Q2: How many PSA values are needed?
A: While this calculator uses two points, more accurate calculation requires 3+ PSA values over 12+ months.

Q3: What affects PSADT accuracy?
A: PSA variability, assay differences, recent procedures (biopsy, DRE), infections, and medications (5-ARIs).

Q4: Can this be used after treatment?
A: PSADT after treatment (especially radiation) may have different prognostic significance than untreated cases.

Q5: What if PSA decreases?
A: The formula gives negative values for decreasing PSA, often reported as "not applicable" or "PSA halving time."