Loading...
Printed on 6/29/2026
For informational purposes only. This is not medical advice.
PSA doubling time (PSADT) measures the rate of rise in PSA and is a key prognostic indicator after prostatectomy or radiation therapy. A short PSADT (< 3 months) is associated with metastatic disease and cancer-specific mortality, while longer doubling times suggest indolent biology. Stratify prostate cancer risk with [CAPRA Score](/tools/capra-score). Assess fitness for systemic therapy with [ECOG Performance Status](/tools/ecog-performance). Monitor renal function for cisplatin eligibility with [eGFR Calculator](/tools/egfr-calculator). Calculate initial PSA density with [PSA Density Calculator](/tools/psa-density).
Formula: PSADT (months) = ln(2) × (days between / 30.44) ÷ ln(PSA₂ / PSA₁)
Save your results with a free account
Keep a history of calculations, favorite tools, and access your dashboard anytime.
Input the earlier and later PSA measurements in ng/mL, and the number of days between them. Both values must be from the same assay platform at the same laboratory for reliable results. PSA2 must be greater than PSA1 — PSADT is not applicable for stable or declining PSA.
PSADT = ln(2) × time interval ÷ (ln(PSA2) − ln(PSA1)). This assumes exponential PSA growth, which approximates cancer kinetics during active disease progression. The result is expressed in months.
PSADT under 3 months: aggressive recurrence — image urgently (PSMA-PET/CT) and consider systemic therapy. 3–10 months: concerning — imaging and treatment escalation discussion. Over 10 months: slower tempo, monitoring may be appropriate. Over 15 months: indolent, observation often reasonable. Use with [CAPRA Score](/tools/capra-score) for full risk assessment.
Urologic oncologists
After radical prostatectomy, PSA should be undetectable (<0.1 ng/mL). Any rise confirms biochemical recurrence. PSADT determines urgency: short PSADT (<3 months) indicates likely early metastatic disease and warrants PSMA-PET imaging; longer PSADT allows for salvage radiation planning.
Radiation oncologists
After radiation therapy, PSA nadirs before rising. PSADT helps distinguish true recurrence from PSA bounce (transient post-radiation rise). Rapid PSADT post-radiation suggests aggressive recurrence requiring systemic therapy; slow PSADT supports continued observation.
Urologic oncologists
During active surveillance for low-risk prostate cancer, shortening PSADT is a trigger for reclassification and consideration of definitive treatment. Most AS protocols recommend re-biopsy or MRI when PSADT falls below 2–3 years, even in the absence of IPSS changes.
Medical oncologists, urologic oncologists
In metastatic prostate cancer, serial PSADT while on ADT assesses treatment response. Decreasing PSADT on ADT (castration-resistant prostate cancer with rising PSA) triggers evaluation of next-generation hormonal agents (enzalutamide, abiraterone) or chemotherapy.
Urologists, oncologists
PSADT translates PSA kinetics into a tangible timeline that helps patients understand their disease trajectory. Explaining that a PSADT of 18 months means PSA takes 18 months to double — versus 2 months for aggressive disease — helps patients make informed decisions about treatment intensity.
Two-point PSADT calculations are sensitive to PSA measurement variability (typically ±5–15%). Using three or more serial values and fitting an exponential curve provides a more accurate and reproducible PSADT estimate. For critical treatment decisions, compute PSADT from all available serial values.
A PSA change from 0.01 to 0.02 ng/mL appears to have a short doubling time but represents values near the lower limit of assay sensitivity. Laboratory variability at these concentrations can produce misleading PSADT calculations. Most guidelines use PSA >0.1–0.2 ng/mL as the threshold for reliable PSADT calculation post-prostatectomy.
For rapidly rising PSA with PSADT under 3 months, conventional imaging (bone scan, CT) has low sensitivity at low PSA values. PSMA-PET/CT detects disease at PSA levels as low as 0.2 ng/mL with much higher sensitivity and specificity. Most NCCN guidelines now prefer PSMA-PET for biochemical recurrence workup.
For post-prostatectomy biochemical recurrence, salvage radiation therapy achieves the best outcomes when started before PSA rises above 0.5 ng/mL. Early detection of rising PSA and prompt PSADT calculation enables timely salvage treatment before macro-metastatic disease develops.
PSA assays from different manufacturers have systematic differences of 5–30%. Using two different labs for serial PSA measurements introduces assay-related PSA 'changes' that are not due to disease. Always recommend patients use the same laboratory for serial PSA monitoring.
PSA doubling time as a prognostic measure was characterized by Freedland et al. (2005, JAMA) in 379 men post-prostatectomy, demonstrating that PSADT <3 months predicted prostate cancer–specific death. NCCN Prostate Cancer Guidelines (2024) incorporate PSADT into the biochemical recurrence management algorithm.
Your PSA doubling time indicates the rate at which your PSA level is rising and is one of the most important prognostic indicators following prostate cancer treatment. A PSADT of less than 3 months suggests very aggressive tumor biology, is strongly associated with the development of distant metastases, and is an independent predictor of prostate cancer-specific mortality. A PSADT of 3 to 10 months is concerning and typically prompts imaging studies (bone scan, CT, or PSMA-PET) and consideration of treatment escalation such as salvage radiation or androgen deprivation therapy. A PSADT of 10 to 15 months suggests moderately paced disease that may be suitable for close monitoring. A PSADT greater than 15 months indicates relatively indolent biology, and observation with serial PSA monitoring is often reasonable.
It is essential to note that PSADT calculations are most reliable when based on at least three PSA values over an adequate time interval. A two-point calculation, while commonly used, is more susceptible to PSA measurement variability and may not accurately represent the true kinetics of disease progression.
PSA doubling time is primarily used after definitive treatment for prostate cancer — radical prostatectomy or radiation therapy — when a rising PSA (biochemical recurrence) is detected. It helps distinguish patients with aggressive recurrences who need urgent salvage therapy from those with slow PSA rises who may safely be observed.
PSADT is also used during active surveillance for low-risk prostate cancer, where a rapidly shortening doubling time may trigger reclassification and recommend definitive treatment. In the setting of castration-resistant prostate cancer, PSADT helps assess the tempo of disease progression and guides decisions about initiating or changing systemic therapy.
PSADT assumes exponential PSA growth, which is a simplification. Actual PSA kinetics can be non-linear, especially early after treatment when benign sources of PSA (residual prostate tissue, prostatitis) may contribute to fluctuations. A PSA bounce after radiation therapy — a transient rise followed by a decline — can produce misleading PSADT values if measured during this period.
The calculation requires a rising PSA (PSA2 greater than PSA1). If PSA is stable or declining, PSADT is not applicable. Additionally, very low absolute PSA values (less than 0.1 ng/mL) are near the lower limit of assay sensitivity, and small measurement errors can dramatically affect the calculated doubling time.
PSADT should be interpreted alongside other clinical factors including Gleason score, pathological stage, time from treatment to biochemical recurrence, and imaging findings. A short PSADT with negative imaging may warrant a different approach than a short PSADT with visible metastatic disease. The result is a prognostic indicator, not a treatment recommendation in isolation.
For related assessments, see PSA Density, CAPRA Score and Prostate Volume.
Disclaimer: This tool is for educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider with questions about your health.
April 21, 2026 · trust-baseline
Clinical trust metadata enabled for this tool page with structured review/version fields.
Calculate PSA density (PSAD) to differentiate BPH from prostate cancer. PSAD ≥0.15 ng/mL/mL indicates higher cancer risk and may warrant biopsy even with borderline total PSA levels.
OpenUrologyCalculate the UCSF-CAPRA score for prostate cancer risk stratification. Low (0–2), Intermediate (3–5), High (6–10) risk categories guide treatment choice and predict biochemical recurrence.
OpenUrologyEstimate prostate volume from TRUS or MRI measurements using the ellipsoid formula (π/6 × L × W × H). Normal prostate is 20–30 mL; volume >40 mL suggests clinically significant BPH.
Open