Understanding PSA Kinetics: A Patient's Guide

Your doctor mentions "PSA kinetics" or "PSA dynamics"—what do these terms mean? PSA kinetics refers to how your PSA changes over time, not just its absolute value. Understanding these concepts helps you participate meaningfully in your care.

What Are PSA Kinetics?

PSA kinetics encompasses three related measurements:

1. PSA Velocity (PSAV): How much PSA rises per year
2. PSA Doubling Time (PSADT): Time for PSA to double
3. PSA Density (PSAD): PSA relative to prostate size

Together, these provide a more complete picture than any single PSA value.

PSA Velocity (PSAV)

What It Measures

PSA Velocity measures the absolute change in PSA per year:

What's Normal?

• Normal: <0.35 ng/mL/year (consistent with BPH)
• Borderline: 0.35-0.75 ng/mL/year
• Elevated: >0.75 ng/mL/year (increased cancer risk)

Limitations

PSAV assumes linear growth, but cancer typically grows exponentially. That's why PSADT is often more useful.

PSA Doubling Time (PSADT)

What It Measures

PSADT measures how long it takes for PSA to double. This reflects exponential growth patterns:

Use our PSADT Calculator to compute this automatically.

Interpretation

• >24 months: Low risk, indolent
• 12-24 months: Intermediate
• <12 months: Elevated risk
• <6 months: High risk, aggressive

Why It Matters

PSADT better reflects tumor biology because cancer cells grow exponentially, not linearly. A short doubling time suggests rapidly dividing cells.

PSA Density (PSAD)

What It Measures

PSA Density adjusts PSA for prostate size:

Calculate yours with our Prostate Volume Calculator.

Why It Matters

Larger prostates produce more PSA even without cancer. A PSA of 8 means something different in a 25cc prostate versus an 80cc prostate:

• 8 ÷ 25 = 0.32 (concerning)
• 8 ÷ 80 = 0.10 (likely benign)

Thresholds

• <0.10: Low cancer risk
• 0.10-0.15: Borderline
• >0.15: Elevated cancer risk

How They Work Together

Consider this example:

Analysis:

• PSAV: (6.5-5.0)/2 = 0.75 ng/mL/year (borderline elevated)
• PSADT: ~5 years (reassuring)
• PSAD: 6.5/55 = 0.12 (borderline)

Conclusion: Despite elevated PSA, kinetics suggest BPH more likely than cancer. Continued monitoring reasonable; MRI might be considered.

Common Questions

Which metric is most important?

Context determines importance:

• Pre-diagnosis: PSA Density often most informative
• Active surveillance: PSADT is key trigger
• Post-treatment: PSADT predicts recurrence behavior

How many PSA values do I need?

For reliable kinetics:

• Minimum: 2 values for simple calculation
• Ideal: 3+ values spanning 6-12+ months
• Same laboratory for all measurements

Can medications affect kinetics?

Yes:

• 5-ARIs (finasteride, dutasteride): Cut PSA in half; must double reported value
• Testosterone therapy: Can increase PSA

Tracking Your PSA Kinetics

1. Keep a log of all PSA values with dates
2. Note the laboratory (different assays vary)
3. Calculate kinetics between appointments using our PSADT Calculator
4. Know your prostate volume for density calculations
5. Bring your tracking to doctor visits

Key Takeaways

Calculate your PSA kinetics with our free PSADT Calculator and Volume Calculator.