Does transrectal ultrasound probe configuration really matter? End fire versus side fire probe prostate cancer detection rates.

PURPOSE We compared prostate cancer detection rates for the 2 most commonly used transrectal ultrasound prostate biopsy probes, end fire and side fire, to determine whether the probe configuration affects detection rates. MATERIALS AND METHODS We evaluated 2,674 patients who underwent initial prostate biopsy between 2000 and 2008 with respect to prostate specific antigen, biopsy technique and pathological findings. Patients were divided into 1,124 in whom biopsies were performed with an end fire probe and 1,550 in whom biopsies were performed with a side fire probe. RESULTS There was a significant difference in the overall cancer detection rate in the end vs side fire arms (45.8% vs 38.5%, p <0.001). In the subsets of patients with prostate specific antigen greater than 4 to 10 ng/ml or less and greater than 10 ng/ml a significant difference persisted (46.4% vs 38.9% and 61.7% vs 49.1%, p <0.004 and <0.015, respectively). There was also a significant difference in detection rates between probes in those who underwent 8 to 19 biopsy cores (p <0.009). Biopsies of greater than 20 cores failed to attain statistical significance (p >0.105). We also found that prostate volume, patient age, prostate specific antigen and hypoechoic findings were independent variables for predicting cancer detection on multivariate analysis (p <0.001). CONCLUSIONS The type of probe significantly affects the overall prostate cancer detection rate, particularly in patients with prostate specific antigen greater than 4 ng/ml and/or nonsaturation (8 to 19 cores) prostate biopsy. This may be because the end fire probe allows better mechanical sampling of the lateral and apical regions of the peripheral zone, where cancer is most likely to reside. We set the stage for a randomized, controlled trial to confirm our observations.