Reliability of small amounts of cancer in prostate biopsies to reveal pathologic grade

To examine grade reliability when biopsies contain very small amounts of prostate cancer. Prostate biopsy findings are known to undergrade prostate cancer compared with the pathologic specimens yet remain the only grade guiding disease management.

The presence of a clinically significant grade change from biopsy cores to matched prostatectomy specimens was examined in 371 patients. The biopsies were characterized for primary and secondary Gleason grade, number of positive cores, and total linear length of cancer. The pathologic specimens were characterized for cancer volume and relative percentage by grade. The rates of upgrading or downgrading were tested against all clinical and biopsy information for any significant predictive value.

The overall rate of upgrading was 40.7% and downgrading was 16.1%. Upgrading was constant and independent of any clinical or biopsy tumor volume indexes. Specifically, when cancer was present in only one biopsy core and measured 2 mm or less (n = 48), it was just as predictive of the pathologic grade as that from any greater number of positive cores and any greater extent of cancer length present. Downgrading was less frequent for biopsies with small amounts of cancer.

Histologic grading from small amounts of cancer in prostate biopsies is reliable and not more prone to grading errors. A repeat biopsy for these patients may not be indicated.