Characteristics and clinical significance of prostate cancers missed by initial transrectal 12-core biopsy

• To characterize prostate cancers missed by initial transrectal 12-core biopsy.

• Between 2002 and 2008, 715 men with prostate-specific antigen levels in the range 2.5-20 ng/mL or abnormal digital rectal examination underwent three-dimensional 26-core prostate biopsy (i.e. a combination of transrectal 12-core biopsy and transperineal 14-core biopsy) on initial examination. • Of the 257 patients diagnosed with cancer, 120 patients subsequently underwent radical prostatectomy. • Cancers were grouped into TR12-negative cancers (i.e. not detected through transrectal 12-core biopsy but detected through transperineal 14-core biopsy) and TR12-positive (i.e. detected through transrectal 12-core biopsy) cancers. • Clinicopathological characteristics of the TR12-negative and TR12-positive cancers were evaluated.

• TR12-negative cancers comprised 21% of the three-dimensional 26-core biopsy-detected cancers. • The frequency of cancers with a biopsy Gleason score ≤ 6 and that of cancers with a biopsy primary Gleason grade ≤ 3 was higher in TR12-negative cancers, at 58% and 83%, respectively, than in TR12-positive cancers, at 25% (P < 0.001) and 53% (P < 0.001), respectively. • The median number of positive cores in TR12-negative cancers was two out of 26. • TR12-negative cancers were more frequently located anteriorly than posteriorly. • The incidence of the TR12-negative cancers was not associated significantly with any clinical variable.

• Many of the cancers missed by initial transrectal 12-core biopsy are probably low-grade and low-volume diseases, although initial transrectal 12-core biopsy has a small but definite risk of missing anterior significant cancers.