Purpose: Sampling error is an inherent problem of prostate biopsy. Consequently the determination of whether a given carcinoma is clinically significant based on biopsy results is problematic. We assess the dimensions of sampling error and, thereby, provide insight into the potential value of prognostic markers applied to needle biopsies.
Materials and methods: We constructed 3-dimensional computer models of 21 prostatectomy specimens, including outlines of carcinomas, regions of abnormal E-cadherin expression and individual Gleason patterns. The 6 random systematic core biopsy technique and modifications were simulated using a computer algorithm.
Results: In 6 of 21 cases the area of abnormal E-cadherin expression and/or high grade carcinoma was not sampled on 6 random systematic core biopsy. The areas missed were either small or inconsistently under sampled regions of the prostate. Modifying the placement of biopsy needles improved the detection of these features. In addition, percent tumor in the needle appeared to be well correlated to percent tumor in the prostate (r = 0.891, r2 = 0.642).
Conclusions: To avoid underestimating the aggressiveness of prostatic carcinoma at least 6 biopsies should be taken from each patient. A more extensive sampling is probably not warranted in all patients but it may prove useful in those in whom extent of disease is unclear or whose general health makes treatment decisions difficult. A reliable estimate of tumor volume in the prostatectomy specimen can be made based on relative amount of tumor in the biopsy specimen on an individual basis.