Thursday, 19 October 2017

PSA (prostate specific antigen) density

PSA density (ng/mLor ng/mL/cc) is calculated preoperatively during the biopsy procedure by using transrectal ultrasound by dividing the maximum preoperative PSA value and prostate volume [1]. The latter is calculated based on the ellipse dimension theory formula [2] (D1 × D2 × D3 × pi/6), where D1 is the maximum transverse diameter, D2 is the maximum anteroposterior diameter, D3 is the maximum longitudinal diameter, and pi is a mathematical constant approximately equal to 3.14.
A study of a large cohort of patients (1662 patients) found a significant trend of worsening pathological features as PSA density increases [3]. Other studies [4,5] found that PSA density (using a pathological weight of the surgical specimen) was a better predictor of extracapsular disease, positive surgical margins, seminal vesicle invasion, lymph node invasion and biochemical recurrence than PSA.
«It is used because an elevated PSA might not arouse suspicion in a man with a very enlarged prostate. The use of PSA density to interpret PSA results is controversial because prostate cancer might be overlooked in a man with an enlarged prostate» [6].
Bibliographic references:
[1] Sfoungaristos S, Perimenis P. Evaluating PSA Density as a Predictor of Biochemical Failure after Radical Prostatectomy: Results of a Prospective Study after a Median Follow-Up of 36 Months. ISRN Urol. 2013 May 16;2013:984951. Available at: https://doi.org/10.1155/2013/984951.
[2] Wolff JM, Boeckmann W, Mattelaer P, et al. Determination of prostate gland volume by transrectal ultrasound: correlation with radical prostatectomy specimens. Eur Urol. 1995;28(1):10-2. Available at: https://doi.org/10.1159/000475012.
[3] Kundu SD, Roehl KA, Yu X, et al. Prostate specific antigen density correlates with features of prostate cancer aggressiveness. J Urol. 2007 Feb;177(2):505-9. Available at: https://doi.org/10.1016/j.juro.2006.09.039.
[4] Freedland SJ, Wieder JA, Jack GS, et al. Improved risk stratification for biochemical recurrence after radical prostatectomy using a novel risk group system based on prostate specific antigen density and biopsy Gleason score. J Urol. 2002 Jul;168(1):110-5. Available at: http://dx.doi.org/10.1016/S0022-5347(05)64841-0.
[5] Sfoungaristos S, Perimenis P. PSA density is superior than PSA and Gleason score for adverse pathologic features prediction in patients with clinically localized prostate cancer. Can Urol Assoc J. 2012 Feb;6(1):46-50. Available at: https://doi.org/10.5489/cuaj.11079.
[6] Definition of PSA density. Phoenix5org. 2002. Available at: http://www.phoenix5.org/glossary/PSA_density.html. Accessed October 19, 2017.