PSA Doubling Time Prostate Cancer Calculator

PSA Doubling Time Formula:

\[ T_d = \frac{\ln(2) \times (t_2 - t_1)}{\ln(PSA_2 / PSA_1)} \]

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 guide treatment decisions.

2. How Does the Calculator Work?

The calculator uses the following formula:

\[ T_d = \frac{\ln(2) \times (t_2 - t_1)}{\ln(PSA_2 / PSA_1)} \]

Where:

\( T_d \) — PSA doubling time (months)
\( PSA_1 \) — Initial PSA value (ng/mL)
\( PSA_2 \) — Current PSA value (ng/mL)
\( t_1 \) — Time of initial PSA measurement (months)
\( t_2 \) — Time of current 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 Importance

Details: Shorter PSADT (<3 months) is associated with more aggressive disease, higher risk of metastasis, and poorer prognosis. PSADT helps guide decisions about active surveillance vs. treatment.

4. Using the Calculator

Tips: Enter PSA values in ng/mL and time points in months. Ensure PSA2 is more recent than PSA1 and both PSA values are positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is a significant change in PSADT?
A: Generally, PSADT <12 months is considered clinically significant, with <6 months indicating higher risk and <3 months suggesting very aggressive disease.

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

Q3: Does PSADT apply to all prostate cancer patients?
A: It's most useful for monitoring after primary treatment (surgery/radiation) or during active surveillance.

Q4: Can PSADT be used during ADT (androgen deprivation therapy)?
A: PSADT interpretation differs during ADT as PSA should be declining. Rising PSA during ADT suggests castration-resistant disease.

Q5: What factors can affect PSADT accuracy?
A: PSA variability, recent procedures (biopsy, cystoscopy), infections (prostatitis), and medications (5α-reductase inhibitors) can affect calculations.