1. What is PSA Doubling Time?

PSA Doubling Time (PSADT) is the length of time it takes for the prostate-specific antigen (PSA) level to double. It's an important prognostic indicator in prostate cancer management, particularly for monitoring disease progression after treatment.

2. How Does the Calculator Work?

The calculator uses the PSADT formula:

Where:

• \( slope \) — The slope from ln(PSA) vs time plot
• \( \ln(2) \) — Natural logarithm of 2 (approximately 0.693)

Explanation: The slope is calculated from at least two PSA measurements over time using the formula: slope = (ln(PSA2) - ln(PSA1)) / time.

3. Importance of PSADT Calculation

Details: PSADT helps clinicians assess prostate cancer aggressiveness, predict biochemical recurrence after treatment, and guide treatment decisions. A shorter doubling time typically indicates more aggressive disease.

4. Using the Calculator

Tips: Enter two PSA values in ng/mL and the time between measurements in months. All values must be valid (PSA > 0, time > 0).

5. Frequently Asked Questions (FAQ)

Q1: What is considered a significant PSADT?
A: Generally, PSADT less than 3 months indicates aggressive disease, while greater than 15 months suggests indolent disease.

Q2: How many PSA measurements are needed?
A: While two measurements provide an estimate, more measurements over time give a more accurate calculation of PSADT.

Q3: Does PSADT apply to all prostate cancer patients?
A: PSADT is most useful for monitoring patients after primary treatment (surgery or radiation) and those on active surveillance.

Q4: Can PSADT be used for untreated patients?
A: Yes, PSADT can help determine the aggressiveness of untreated prostate cancer and guide treatment decisions.

Q5: Are there limitations to PSADT calculation?
A: PSADT may be less reliable with very low PSA values, during hormonal therapy, or when PSA fluctuations are minimal.