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 PSA Date (t1):

months ago

Current PSA Date (t2):

months ago

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 guide treatment decisions.

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 ago)
\( t2 \) — Time of current PSA measurement (months ago)

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

3. Clinical Importance

Details: Shorter PSADT (<3 months) suggests aggressive disease, while longer PSADT (>12 months) indicates slower progression. PSADT helps in decision-making for active surveillance vs. treatment.

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: What is a concerning PSA doubling time?
A: Generally, <12 months is concerning, <6 months suggests aggressive disease, and <3 months indicates highly aggressive prostate cancer.

Q2: How many PSA values are needed for accurate calculation?
A: While two points give an estimate, more measurements over time provide greater accuracy in determining the trend.

Q3: Does PSADT apply to post-treatment monitoring?
A: Yes, PSADT after radical prostatectomy or radiation therapy is an important prognostic factor for biochemical recurrence.

Q4: What factors can affect PSA doubling time?
A: Prostate procedures, infections, medications (5-alpha reductase inhibitors), and benign prostatic hyperplasia can affect PSA levels.

Q5: How often should PSA be measured for doubling time?
A: Typically every 3-6 months for active surveillance, but frequency depends on individual risk factors and prior PSADT.