Initial extended transrectal prostate biopsy--are more prostate cancers detected with 18 cores than with 12 cores?

We retrospectively investigated the detection rates of prostate cancer, high grade prostatic intraepithelial neoplasia and atypical glands suggestive of carcinoma by initial 18 and 12-core prostate biopsy.

A total of 3,460 consecutive patients with prostate specific antigen between 2.5 and 15 ng/ml underwent 12 (1,684) or 18 (1,776) core prostate biopsy under local anesthesia at 2 departments that adopted the same indications for performing biopsy. Biopsies were evenly distributed throughout the prostate in 6 sectors. In the 12-core prostate biopsy group 2 samples were obtained from each sector and in the 18-core prostate biopsy group 1 additional core was taken from each sector.

The cancer detection rate in patients who underwent 18-core prostate biopsy was not different from the rate in those who underwent 12-core prostate biopsy (39.9% and 38.4%, p = 0.37), nor did the detection of atypical glands suggestive of carcinoma differ significantly between the 2 groups (2.9% and 3.3%, respectively, p = 0.33). However, 18-core prostate biopsy detected a significantly higher percent of cases of high grade prostatic intraepithelial neoplasia (20.0% vs 12.9%, p = 0.001). The cancer detection rate was higher with 18 than with 12-core prostate biopsy in patients with a prostate volume of 55 cc or greater (31.5% vs 24.8%, p = 0.01) but not in those with a prostate volume of less than 55 cc (54.3% and 53.0%, respectively, p = 0.7). Moreover, we determined that patients with positive digital rectal examination findings do not need 18-core prostate biopsy as opposed to 12-core prostate biopsy.

Compared with 12-core prostate biopsy, 18-core prostate biopsy detects significantly more cases of high grade prostatic intraepithelial neoplasia. However, 18-core prostate biopsy detects a significantly higher number of cancer only in patients with a prostate volume of 55 cc or greater.