Calculate PSA doubling time (PSADT) and velocity from serial PSA values, then review the trend with a cautious kinetic context and illustrative future projections.
PSA doubling time (PSADT) describes how quickly PSA is rising across serial measurements. It is a growth-rate calculation rather than a single-threshold test, which is why it is often used to add context when the question is not simply "is PSA elevated?" but "how fast is the pattern changing over time?"
This calculator derives PSADT from two or three PSA values, calculates PSA velocity, and shows an illustrative projection if the same exponential trend continued. That makes it useful as a kinetics worksheet for recurrence follow-up, surveillance review, or serial PSA discussions. It is still only one layer of context. Assay differences, prostatitis, recent procedures, benign enlargement, absolute PSA level, imaging, pathology, and prior treatment all affect how the number should be interpreted.
PSA doubling time is most useful when the main question is how quickly the marker is rising. This page keeps the serial PSA values, elapsed time, velocity, and a simple projected trend in one place so the growth-rate pattern can be reviewed without pretending that one kinetic number decides treatment by itself.
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. On this page that lands in the intermediate kinetic range, which usually warrants closer review of the broader recurrence picture rather than an automatic treatment decision from the growth rate alone.
PSA doubling time is a kinetic measure, so it is more informative than a single elevated value when deciding whether the pattern looks indolent or aggressive. A short doubling time usually signals more active disease biology, while a long doubling time suggests slower change.
Two values are enough to calculate a number, but more points and longer spacing usually produce a steadier trend. The result is most trustworthy when the same assay is used over time and the lab values are not influenced by transient inflammation or recent procedures.
PSADT is often paired with the biochemical recurrence definition, MRI findings, and treatment history. The calculator is most useful when it supports that broader clinical picture rather than replacing it.
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This page calculates PSA doubling time with the standard natural-log equation from two PSA values and their time interval, adds PSA velocity as a simple linear annualized rate, and optionally recomputes a three-point doubling time when a third PSA value is entered. It also shows an illustrative projection if the same exponential trend continued, purely so the user can visualize how quickly the marker is rising.
The result is a kinetics worksheet, not a treatment algorithm. Shorter doubling times are commonly read as a more concerning pattern after recurrence, but the meaning still depends on assay consistency, the recurrence definition, absolute PSA level, pathology, imaging, prior treatment, and the broader clinical picture.
Shorter doubling times, especially under 6 to 12 months, are usually treated as more concerning kinetic patterns than slower rises. The exact implication still depends on context such as recurrence definition, imaging, pathology, absolute PSA level, and treatment history.
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, but only as one signal. MRI findings, repeat biopsy results, gland size, infection, and the baseline disease features are all part of the surveillance picture, so the kinetics should not be read in isolation.
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.