PSA Doubling Time Explained
PSA doubling times are evaluated in patients with prostate cancer who have undergone prostatectomy or definitive radiation therapy and present biochemical recurrence.
Biochemical recurrence may be defined as:
- PSA ≥0.2 ng/mL – following radical prostatectomy;
- PSA rise of ≥2 ng/mL above the nadir PSA level – following radiation therapy.
PSADT is used as an indicator of biochemical and clinical progression. However, please note that since prostate specific antigen elevations may accompany different conditions, including benign prostatic hyperplasia (BPH), PSA doubling time has a limited value in prostate cancer screening and diagnosis.
Shorter PSADTs reflect faster increases in prostate specific antigen whilst longer PSADTs reflect slower increases in PSA levels.
A doubling time > 6 months is considered a positive predictor, with less likelihood of aggressive treatment necessary in the future and longer survival rates.
A doubling time < 6 months is considered a negative predictor, with prolonged treatment likely to be needed.
PSA doubling time = ln (2) / PSA Slope
PSA Slope = (ln (PSA level 2) – ln (PSA level 1)) / Time (no. of months)
The PSA velocity is the rate of PSA rise, expressed in nanograms/mL/year:
Velocity = (PSA level 2 – PSA level 1) / Time (no. of months)
Time (no. of months) = Second Test Date - First Test Date
PSADT may be used as a survival measure in prostate cancer, as being predictive of the risk for development of metastatic disease. In the study by Pound et al. the longest metastatic disease-free survival was recorded in patients who met:
- PSADT > 10 months;
- Gleason Scores 5-7;
- Length of time to biochemical recurrence >2 years.
Pound CR, Partin AW, Eisenberger MA, Chan DW, Pearson JD, Walsh PC. Natural history of progression after PSA elevation following radical prostatectomy. JAMA. 1999;281(17):1591-1597.
Vickers AJ, Brewster SF. PSA Velocity and Doubling Time in Diagnosis and Prognosis of Prostate Cancer. Br J Med Surg Urol. 2012; 5(4):162-168.
Ponholzer A, Popper N, Breitenecker F, et al. Proposal for a standardized PSA doubling-time calculation. Anticancer Res. 2010; 30(5):1633-1636.