Calculate PSA doubling time (PSADT) and velocity from serial PSA values, assess recurrence risk after prostatectomy or radiation, and project future PSA levels.
PSA doubling time (PSADT) is one of the most powerful prognostic biomarkers in prostate cancer, measuring the exponential rate at which prostate-specific antigen increases over time. It quantifies tumor biology more directly than a single PSA value, since a rapidly doubling PSA indicates aggressive disease while slowly rising PSA suggests indolent biology.
This calculator determines PSADT from two or three serial PSA measurements using the natural logarithm formula, computes PSA velocity (linear rate of change), categorizes risk using established PSADT thresholds, and projects future PSA levels assuming continued exponential growth. It supports clinical decision-making in three major contexts: biochemical recurrence after radical prostatectomy or radiation therapy, active surveillance monitoring, and pre-treatment risk stratification.
A PSADT under 3 months is associated with prostate cancer-specific mortality exceeding 30% within 10 years after biochemical recurrence, while a PSADT over 15 months carries a cancer-specific mortality under 2%. This dramatic prognostic separation makes PSADT essential for triaging patients between observation, salvage local therapy, and systemic treatment. Accuracy improves with more PSA data points and longer observation intervals.
This calculator provides precise PSA doubling time calculation using the logarithmic formula, risk stratification across multiple clinical contexts, PSA velocity computation, future PSA projections, and supports three-point PSADT for validation — all essential for prostate cancer treatment decisions after recurrence or during active surveillance. Keep these notes focused on your operational context. Tie the context to the calculator’s intended domain.
PSADT = Time (months) × ln(2) / ln(PSA₂ / PSA₁). PSA Velocity = (PSA₂ − PSA₁) / Time (months) × 12 (annualized). Projected PSA = PSA₂ × 2^(months / PSADT).
Result: PSADT = 9.8 months, PSA Velocity = 1.6 ng/mL/yr, Moderate risk
PSA went from 1.2 to 2.8 in 12 months. Doubling time = 12 × 0.693 / ln(2.8/1.2) = 9.8 months. This falls in the moderate risk category, suggesting salvage treatment should be considered.
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A PSADT under 3 months indicates very aggressive disease biology and is associated with rapid progression and higher cancer-specific mortality. PSADT under 6 months is generally considered high-risk and warrants systemic therapy consideration.
Minimum of two values at different time points. Three or more values improve accuracy. Ideally, measurements should span at least 3–6 months for reliable kinetic calculations.
PSA velocity is the linear rate of change (ng/mL/year). PSADT measures exponential growth rate. PSADT is generally preferred because tumor growth is exponential, making doubling time more biologically meaningful.
After radical prostatectomy: PSA ≥0.2 ng/mL with a confirmatory rise. After radiation: PSA rise ≥2 ng/mL above the nadir (Phoenix definition). The context affects how PSADT is interpreted clinically.
Yes. On active surveillance, a PSADT <3 years raises concern for reclassification and is one trigger for repeat biopsy or treatment consideration. However, it should be interpreted alongside MRI and biopsy findings.
If PSA is declining, the PSADT equation does not apply (you cannot take the log of a ratio <1). A declining PSA is a favorable sign suggesting treatment response or absence of active disease.