The lack of predictive value of prostate specific antigen density in the detection of prostate cancer in patients with normal rectal examinations and intermediate prostate specific antigen levels

Abstract

Purpose: The management of patients with a normal digital rectal examination and a prostate specific antigen (PSA) level of 4.0 to 10.0 ng./ml. remains controversial. To improve the specificity of cancer detection in this group, PSA density has been recommended with biopsies based on a PSA density of 0.15 or more. To evaluate PSA density as a discriminator of prostate cancer we enrolled patients in a prospective study.

Materials and methods: A prospective evaluation was done of 44 consecutive patients with a palpably normal digital rectal examination and a serum PSA level of 4.0 to 10.0 ng./ml. enrolled during a 13-month period. All patients underwent transrectal ultrasound with sextant biopsies regardless of calculated PSA density.

Results: Overall, 8 of 44 men (18%) had prostate cancer. There was no significant difference in the mean PSA density between the patients with positive and negative biopsies (mean 0.12 and 0.15, respectively, p = 0.258). Also, there was no significant association between PSA or PSA density and a positive biopsy in multivariate analysis (p = 0.863). Receiver operating characteristic curves for PSA and PSA density failed to demonstrate any superior benefit for PSA density in this patient population. A PSA density of 0.15 was an unreliable indicator of cancer (sensitivity 12.5%, specificity 61.1% and positive predictive value 6.7%).

Conclusions: In our study, PSA density did not discriminate between patients with positive and negative biopsies, and in fact most cancers would not have been detected if a PSA density of 0.15 or more had been used as the sole indication for biopsy. Therefore, we recommend systematic biopsies in these patients independent of calculated PSA density.