The prognostic value of different forms of prostate specific antigen and their ratios in patients with prostate cancer
Article first published online: 24 DEC 2001
Volume 84, Issue 9, pages 1021–1027, December 1999
How to Cite
Björk, Lilja and Christensson (1999), The prognostic value of different forms of prostate specific antigen and their ratios in patients with prostate cancer. BJU International, 84: 1021–1027. doi: 10.1046/j.1464-410x.1999.00345.x
- Issue published online: 24 DEC 2001
- Article first published online: 24 DEC 2001
- Prostate cancer;
- prostate-specific antigen;
- percentage free PSA;
- PSA forms;
To assess the prognostic value for patient survival of different forms of PSA and ratios thereof, before treatment for prostate cancer, by considering the forms and ratios both as independent markers and by comparing them with other commonly used prognostic markers, e.g. tumour grade, local stage (T-stage) and absence or presence of skeletal metastases (M-stage).
Patients and methods
Blood samples were collected consecutively from men diagnosed with prostate cancer at our department in 1988. From this group, 66 men were followed until death, or for ≥9 years. Twenty-five patients died from their prostate cancer and 21 from other causes during the follow-up period. Forty-eight patients received hormonal treatment, whereas 18 remained untreated or received no treatment for their cancer before they died from other causes. Assays measuring the serum levels of free prostate specific antigen (fPSA), PSA complexed to α1-antichymotrypsin (PSA-ACT), and total PSA (tPSA) were used to calculate the percentage of free to total PSA (f/tPSA) fPSA/ACT and ACT/tPSA at diagnosis. Based on the initial levels or ratios of the PSA forms, the patients were divided into three numerically comparable groups (tertiles) for survival analysis. Prognostic factors predicting patient survival were evaluated using univariate (Kaplan–Meier life-tables with the log-rank test) and multivariate techniques (Cox proportional hazards regression model).
Univariate analysis using the log-rank test showed that the serum level of each molecular form of PSA, i.e. tPSA (P=0.001), PSA-ACT (P<0.001) and fPSA (P<0.001), as well as grade (P<0.001), T-stage (P=0.00355) and M-stage (P<0.001), provided statistically significant prognostic information. Log-rank tests showed that none of the ratios, i.e. f/tPSA, fPSA/ACT and ACT/tPSA, were informative of prognosis (P>0.05). However, in a multivariate analysis regression model, not only M-stage (risk ratio 4.2; P=0.026) and grade (risk ratio 2.6; P=0.022), but also f/tPSA (risk ratio 1.8; P=0.037), provided significant prognostic information.
The values of tPSA, fPSA and PSA-ACT, as well as grade and T- and M-stage, are all independent prognostic factors of prostate cancer survival. In a multivariate analysis, not only M-stage and grade but also f/tPSA provided significant prognostic information.