Free PSA and prostate volume on the diagnosis of prostate carcinoma

RESUMO

Objective: To analyse the influente of prostate volume on the performance of total prostate specific antigen (tPSA) and free PSA (fPSA) on the diagnosis of prostate adenocarcinoma. Methods: A total of 188 patients underwent transrectal ultrasound guided biopsies (10-12 cores) due to prostate nodes detected by digital rectal examination and/or tPSA range of 2.5-l0ng/ml. Mean age was 65.7±8.7 years. 19/100 (19 percent)(GI) patients with prostate volume >40m1 had prostate cancer while the corresponding figure for patients with prostate <40m1 was 26/88 (29.5 percent)(GII). We analyzed the sensitivity and specificity of tPSA at cut-off points of 2.5 and 4ng/ml as well as the influente of the ratio f/tPSA in both groups of patients. Results: In the group GI tPSA sensitivity and specificity were 94.4 percent and 19.5 percent at the cut-off level of 4ng/ml and 100 percent and 6 percent at 2.5ng/ml. The corresponding values for GIl were 76.5 percent and 62.9 percent, and 100 percent and 19.3 percent. In group GI a cut-off of 19 percent for the ratio f/tPSA kept tPSA sensitivity over 90 percent while the specificity increased to 46.2 percentn at cut-off level of 4ng/ml and to 32.9 percent at 2.5ng/ml. In the group GII the ratio f/tPSA was not able to increase the specificity of tPSA at a cut-off level of 4ng/ml without an expressive reduction of sensitivity. On the other side, for this group a cutoff of 16 percent for the f/tPSA ratio rose the specificity to 46.7 percent for a sensitivity over 90 percent. Conclusion: We recommend stratification of patients according to prostate volume to define tPSA cut-off point. The cut-off level of 2.5ng/ml for tPSA combined with f/tPSA ratio of 19 percent in prostates >40ml and 16 percent in prostates <40m1 was a better option for prostate biopsy indication than tPSA at a cutoff of 4ng/ml associated or not with f/tPSA ratio.