Distinguishing clinically important from unimportant prostate cancers before treatment: value of systematic biopsies

PURPOSE: We assessed the ability of diagnostic tests to distinguish clinically unimportant cancers. MATERIALS AND METHODS: We correlated T stage (based on digital examination and ultrasound), prostate specific antigen (PSA), PSA density and pathological features of cancer in systematic biopsy specimens with features of cancer in 170 radical prostatectomy specimens. Clinically unimportant cancers were defined as small (0.5 cm.3 or less), well or moderately differentiated and confined to the prostate. RESULTS: Of the patients 10% had an unimportant cancer. On logistic regression analysis the 2 significant predictors were maximum length of cancer in any core and PSA density. Of 12 patients with maximum cancer length 2 mm. or less and PSA density less than 0.1., 75% had an unimportant cancer compared to 5% of the remaining 158 (p < 0.0005). CONCLUSIONS: Quantitative analysis of systematic biopsy specimens combined with PSA density provides valuable staging information and helps to identify cancers of low biological potential.