Use of prostate-specific antigen and tumor volume in predicting needle biopsy grading error.

Objectives: To study the discrepancy between histologic grades of needle biopsy and prostatectomy specimens and to define the potential role of prostate-specific antigen (PSA), PSA density, and tumor volume in predicting the tumor grade.

Methods: Histopathologic grades on needle biopsy and subsequent radical prostatectomy specimens were compared in 135 patients with clinically organ-confined prostate cancer. The frequency of undergrading (difference of one or more grades) by needle biopsy was then compared to PSA, PSA density, and other preoperative parameters.

Results: The frequency of undergrading by one level was 45% using the M. D. Anderson Hospital (MDAH) system and 47% using the Gleason system. When the tumor grades were classified into two categories, undergrading rates of 26% (low to high grade by the MDAH system) and 21% (moderately well to poorly differentiated by the Gleason system) were noted. Serum PSA and PSA density correlated with the grading error rate: the higher the PSA and PSA density values, the higher the biopsy undergrading rate. PSA showed a significant correlation with undergrading (P = 0.0019). Undergrading occurred in 32% of patients with a PSA more than 4 and 10 ng/mL or less and in 47% of those with a serum PSA more than 10 ng/mL. In all cases when the PSA was 4 ng/mL or less, the needle biopsy results correctly predicted the final tumor grade category. Tumor volume was not associated with frequency of undergrading.

Conclusions: The ability to predict tumor grade can be enhanced by considering the serum PSA value.