The incidence of transition zone prostate cancer diagnosed by transperineal template-guided mapping biopsy: implications for treatment planning.

OBJECTIVES

To report the incidence of transition zone (TZ) cancer in patients undergoing transperineal template-guided mapping biopsy (TTMB) of the prostate gland.

METHODS

Five hundred thirty-nine consecutive patients underwent TTMB by means of an anatomic technique with sampling of 24 defined prostate regions. The position of each biopsy core was recorded in 3 dimensions. For every patient, the location of each positive biopsy core, the number of positive cores, the Gleason score, the percentage involvement of each core, and the presence/absence of perineural invasion was documented.

RESULTS

The median volumetric prostate volume was 56.0 cm(3) with an ellipsoid TZ volume of 20.1 cm(3). The median number of TTMB cores was 58 with a median of 11 TZ cores. Two hundred eighty-seven (53.2%) were diagnosed with prostate cancer. TZ cancer was detected in 130 (45.3%) of patients with prostate cancer but only 6 (4.6%) were confined to the TZ. Overall, 38.9% of TZ cores were positive for malignancy. Of the TZ cancers, 37 (28.5%), 64 (49.2%), and 29 (22.3%) were assigned Gleason scores 6, 7, and 8-10. Compared with a standard 12-core biopsy approach, the results of the TZ biopsy upgraded the Gleason score in 24.6% of patients. Only 4 cancers (3.1%) involving the TZ were classified as clinically insignificant.

CONCLUSIONS

Although only 4.6% of cancers were confined to the TZ, 45.3% of all prostate cancer patients had TZ involvement.