Sunday, 17 June 2018

PSAV (prostate specific antigen velocity)

Total PSA (prostate specific antigen) velocity, in ng/mL/year, is the change in total PSA values over time and it is «calculated as the running average of the rate of change during 3 consecutive visits by the equation 0.5{[(PSA2-PSA1)/(elapsed time in years)]+[(PSA3-PSA2)/(elapsed time in years)]}, where PSA1 is the first of the 3 measurements, PSA2 the second and PSA3 the third. Elapsed time refers to time between the 2 measurements [1]».
The rate of change in serum total PSA over time provides useful information and increases the specificity of PSA for cancer detection. Current recommendations for the use of PSAV include a collection of PSA levels over a period of no less than 18 months and the use of multiple values (minimum of 3) to perform the calculation. PSAV «has been best used in younger men who have elected to begin early detection programs before age 50». It «was designed to help avoid unnecessary, costly, and potentially morbid repeat biopsies in these men» [2]. «A rise in PSA of as little as 0.1 ng/ml per year is worrisome as to the long-term chance of being diagnosed with prostate cancer» [2,3]:

PSA VelocityProstate Cancer Risk by 10 Years
≤0.1 ng/ml/year3%
>0.1 ng/ml/year65%
Source: [2,3].

«Any rapid rise in PSA is worrisome both for the likelihood of developing cancer but of having more serious (high-grade prostate cancer.) A recent study [4] found that men whose PSA jumped more than 2 points in the year prior to being diagnosed had much higher death rate when treated with surgery (radical prostatectomy). Also, patients treated with radiation for prostate cancer whose PSA starts to rise do worse if the PSA doubles in less than 12 months» [2].
In patients with prostate cancer without metastases, those with a rapid PSAV and an otherwise long life expectancy should be encouraged to consider androgen deprivation therapy earlier [5].
A free online calculation can be found here: USRF (Urological Sciences Research Foundation) - PSA Velocity [6], Prostate Cancer Nomograms | Memorial Sloan Kettering Cancer Center [7], and http://www.doubling-time.com/compute-PSA-doubling-time.php [8].

Bibliographic references:
[1] Khan MA, Carter HB, Epstein JI, et al. Can prostate specific antigen derivatives and pathological parameters predict significant change in expectant management criteria for prostate cancer? J Urol. 2003 Dec;170(6 Pt 1):2274-8. Available at: https://doi.org/10.1097/01.ju.0000097124.21878.6b.
[2] PSA Velocity. Aboutcancercom. Available at: http://www.aboutcancer.com/psa_velocity.htm. Accessed June 17, 2018.
[3] Fang J, Metter EJ, Landis P, Carter HB. PSA velocity for assessing prostate cancer risk in men with PSA levels between 2.0 and 4.0 ng/ml. Urology. 2002 Jun;59(6):889-93; discussion 893-4. Available at: https://doi.org/10.1016/S0090-4295(02)01646-1.
[4] D'Amico AV, Chen MH, Roehl KA, Catalona WJ. Preoperative PSA velocity and the risk of death from prostate cancer after radical prostatectomy. N Engl J Med. 2004 Jul 8;351(2):125-35. Available at: https://doi.org/10.1056/NEJMoa032975.
[5] Mohler J, Lee R, Antonarakis E, et al. NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) – Prostate Cancer – Version 2.2018 - March 8, 2018. Nccnorg. 2018. Available at: https://www.nccn.org/professionals/physician_gls/pdf/prostate.pdf. Accessed June 17, 2018.
[6] USRF - PSA Velocity. Usrforg. Available at: https://www.usrf.org/questionnaires/PSA_Velocity.html. Accessed June 17, 2018.
[7] Prostate Cancer Nomograms: PSA Doubling Time | Memorial Sloan Kettering Cancer Center. Mskcc.org. https://www.mskcc.org/nomograms/prostate/psa_doubling_time. Accessed October 26, 2018.
[8] PSA Doubling Time Calculator. Doubling-time.com. http://www.doubling-time.com/compute-PSA-doubling-time.php. Accessed October 26, 2018.