Correlation of minute (0.5 MM or less) focus of prostate adenocarcinoma on needle biopsy with radical prostatectomy specimen: role of prostate specific antigen density.

PURPOSE: Few studies have examined the radical prostatectomy followup of a minute focus of adenocarcinoma on prostate needle core biopsy.
MATERIALS AND METHODS: We searched the surgical pathology data base (1999 to 2000) for patients with a minute focus of Gleason score 6 adenocarcinoma (defined as a single focus less than or equal to a 40 x microscopic field) who subsequently underwent radical retropubic prostatectomy at our institution. Potentially insignificant tumors were defined as those with a radical prostatectomy tumor volume of less than 0.5 cc, Gleason score 6 or less and organ confined disease.
RESULTS: A total of 54 patients (mean age 58 years, range 45 to 70) were evaluated. The average number of prostate cores per biopsy was 6.3. All had Gleason score 6 by study design. Mean prostate specific antigen (PSA) was 6.0 (range 0.8 to 15). Average tumor volume at radical prostatectomy was 0.39 cc. Of the 54 tumors 24 (44%) were 0.1 cc or less. Two-thirds of the tumors were clinically potentially insignificant. Using a PSA density (PSAD) cutoff of 0.15 we identified 30 of 36 patients (83%) with potentially insignificant tumors. Of those with a PSAD of 0.15 or less with clinically significant tumors, 5 of 6 still had relatively small, organ confined tumors with Gleason score less than 7.
CONCLUSIONS: In the era of PSA screening most patients with a minute focus of Gleason score 6 or less adenocarcinoma on needle biopsy had potentially insignificant tumors. However, one-third of patients had clinically significant tumors warranting definitive therapy. The smallest focus of cancer on needle biopsy is not a guarantee of a clinically insignificant tumor. PSAD may have some value within this group in guiding clinicians and patients as to the likelihood of having clinically insignificant tumors.