Micro-focal prostate cancer: a comparison of biopsy and radical prostatectomy specimen features

To study the pathologic features of radical prostatectomy (RP) specimens of patients operated on the basis of a potentially "Insignificant" prostate cancer (Ca P) characterized by one single focus (less than 3mm) of moderately differentiated adenocarcinoma - Gleason score < or =6, out of 6-10 biopsies and to determine which characteristics, if any, are predictive of the presence of a "non significant" prostate cancer in the specimen characterized by a low volume (<0.5 ml) moderately differentiated organ confined, cancer (Gleason score less than 6).

PSA, biopsy features, and surgical specimens of a series of 56 patients submitted to RP for "insignificant Ca P" on TRUS prostate biopsies between 1988 and 2004 were compared regarding the number of tumor foci, Gleason grade and score, tumor volume determined by the cylinder method, as well as extraprostatic extension (EPE) and positive surgical margins (P.SM.).

70% of the patients had multifocal microfocal cancer apart from the index tumor. The presence of grade 4 was ignored by the biopsy in 50% of the cases, however the primary grade was correctly evaluated in more than 70% of the biopsy sets. 42% of the patients had a cancer volume less than 0.5 ml and 29% met the definition of insignificant/unimportant cancer characterized by a moderately differentiated (Gleason score < or =6) of low volume (less than 0.5 ml) however no feature accurately predictive of insignificant cancer could be individualized. In this whole series, only 8% of the patients had EPE. When the pre-operative PSA was <10 ng/ml, 98% of the patients had an organ confined tumor.

Patients diagnosed with prostate cancer on the basis of one single focus less than 3 mm of moderately differentiated (Gleason < or =6) prostate cancer have 30% of chances of harboring an insignificant tumor in their prostate and are therefore, at risk of being overtreated, however there is at this time no specific feature able to identify these patients pre operatively.