Background: The most efficient number and location of prostate biopsies remains a matter of debate.
Objective: To identify the combination (number and location) of sampling sites that permits the detection of 95% of the prostate cancers (PCa) detected by a 24-core biopsy (24PBx).
Design, setting, and participants: Six hundred and seventeen consecutive patients with a suspicion of PCa were prospectively enrolled.
Intervention: A transrectal ultrasound-guided systematic 24PBx was prospectively performed with local anesthesia in an outpatient setting. The 24PBx was obtained by the overlapping of medial sextant, lateral sextant, octant subcapsular, and quadrant transition cores. Before fixation, each single core was individually marked and inked according to the prostatic location sampled.
Measurements: We relied on a classification and regression tree analysis to identify four subgroups of patients with different PCa detection risk at initial biopsy, according to their clinical characteristics. Subsequently, we set the cancer-positive rate of the 24PBx at 100% and calculated PCa detection rates for 255 possible combinations of sampling sites. We selected the most advantageous biopsy scheme (defined as the combination of sampling sites that detected 95% of all the cancers with the minimal number of biopsy cores) for each patient subgroup. Finally, we internally validated the tumor detection rates by using the 10-fold cross-validation method.
Results and limitations: The 24PBx detected PCa in 289 patients (46.8%). The analysis revealed that the most advantageous schemes for patients with a negative digital rectal exam (DRE), prostate volume (PV) < or =60 cm(3), and age < or =65 yr was a combination of a 16-core biopsy. For patients with a negative DRE, PV < or =60 cm(3), and age >65 yr or a negative DRE and PV >60 cm(3), the most advantageous scheme was two different combinations of a 14-core biopsy. Finally, the sampling that permits detection of 95% of cancers in patients with a positive DRE was a combination of a 10-core biopsy.
Conclusions: The most beneficial scheme varied according to the clinical characteristics of the patients. We propose a user-friendly flowchart to identify the most advantageous set of sampling sites according to patients' characteristics.