PSA Doubling Time Calculator

PSA Doubling Time Formula:

\[ td = \frac{\ln(2)}{\left(\frac{\ln(PSA2 / PSA1)}{(t2 - t1)}\right)} \]

Initial PSA (PSA1):

ng/mL

Current PSA (PSA2):

ng/mL

Initial Time (t1):

months

Current Time (t2):

months

PSA Doubling Time (td):

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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 progression.

2. How Does the Calculator Work?

The calculator uses the following formula:

\[ td = \frac{\ln(2)}{\left(\frac{\ln(PSA2 / PSA1)}{(t2 - t1)}\right)} \]

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. Importance of PSA Doubling Time

Details: PSADT is clinically significant because shorter doubling times (e.g., <3 months) are associated with more aggressive prostate cancer and may influence treatment decisions.

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 results, use PSA values measured with the same assay method.

5. Frequently Asked Questions (FAQ)

Q1: What is a normal PSA doubling time?
A: In healthy men, PSA typically doesn't double (effectively infinite doubling time). In prostate cancer, <3 months is concerning, 3-12 months intermediate, and >12 months more favorable.

Q2: How many PSA points are needed for accurate calculation?
A: While two points provide an estimate, 3+ PSA values over time give more reliable doubling time calculations.

Q3: Does PSA doubling time differ after treatment?
A: Yes, effective treatment should significantly lengthen or stabilize PSADT. Shortening after treatment may indicate recurrence.

Q4: Can PSA doubling time predict survival?
A: Yes, shorter PSADT correlates with worse outcomes. PSADT <3 months is associated with higher prostate cancer-specific mortality.

Q5: Are there limitations to this calculation?
A: Accuracy depends on consistent measurement conditions. PSA bounces, infections, or recent procedures can affect results.