Prostate biopsy can be performed using a transrectal or a transperineal approach. In both cases, transrectal ultrasound (TRUS) scan is a fundamental tool for guiding the biopsy needle and for obtaining a complete systematic sampling of the peripheral and transitional zone of the prostate.
Both in the USA and in Europe, the transperineal route has always been less used than the transrectal one, probably because of its greater invasiveness and difficulty of execution.
As the transperineal biopsy needle passes through the prostate parallel to its longitudinal axis, this route could grant a more selective sampling of the peripheral zone [1,2]. Moreover, a further advantage of the transperineal approach could be the easier sampling of the anterior part of the gland in large prostates or re-biopsies .
The literature data show that the transperineal route allows an optimal prostatic sampling with high prostate cancer detection rates [4,5]. Although Emiliozzi et al. reported higher detection rates after transperineal prostate biopsies, currently no high-level evidence is available to prefer one of the two routes .
The aim of this study is to provide a standardization of transperineal prostate biopsy according to our experience and literature data (Table I).
Preparation: Antibiotic prophylaxis and enema
Transperineal prostate biopsy is considered a sterile procedure. For this reason, antibiotic prophylaxis is recommended only for patients with a high risk of infection, such as diabetic or immunosuppressed subjects, patients with a poor general health status, prostheses or cardiac valve pathologies, and those with indwelling vesical catheter or high post-voiding residual. In those patients, fluorquinolones are indicated as first choice antimicrobials. Alternatively, ampicillin, beta-lactamase inhibitors, cephalosporins or cotrimoxazole can be used as second choice antibiotics. For patients with cardiac valve pathologies or prostheses, double antibiotic prophylaxis with ampicillin/vancomicin associated to aminoglicosides is indicated . No univocal indication exists concerning the length of antibiotic prophylaxis in these patients. Similarly to what happens with the transrectal route, prophylaxis should be ?prolonged? for 3 days .
In our clinical practice, we prefer to use antimicrobial prophylaxis in all patients scheduled for prostate biopsy. Our scheme includes a fluorquinolone single-dose before the procedure. In our series, clinically significant urinary tract infections occurred in less than 1% of cases. Only 3 patients (0.6%) of the 480 prospectively evaluated needed hospitalisation for fever and urinary tract infections .
Roughly 80% of urologists will prescribe an enema in preparation for transrectal prostate biopsy . The reduction of the bacterial load on rectal mucosa may decrease procedure-related infections .
In transperineal biopsies, as the needle is not contaminated by faecal material, a preparation enema may be pointless. Nevertheless, currently we prefer patients to undergo an enema some hours before the procedure. In this way it is possible to reduce the discomfort due to the concomitant presence of the transrectal probe and faecal material in the rectum and to improve the quality of the ultrasound image.
Original transperineal biopsy technique
The patient is placed in the lithotomy position, and the perineal area is shaved and disinfected. TRUS is then performed. Routinely we use a 7.75 MHz linear probe. The ultrasound evaluation includes the measure of prostatic diameters, the estimation of prostate gland and transitional zone volumes, the description of possible suspicious areas in peripheral or transition zone, and the evaluation of prostatic capsule and seminal vesicles.
For the execution of the periprostatic nerve block and for the following biopsies, some authors use a double access situated on the two sides of the midline above the anus at a 45-degree angle from midline at about 15 mm from anus . In our experience we prefer a single transperineal access on the midline 1.5 cm above the anus, as described in 2000 by Milani et al. . Though presenting a theoretically higher risk of bulbar urethra and corpus spongiosus lesions, median access reduces the risk of lesions to the bulbo-urethral arteries and perineal haematomas, thus improving the tolerability of the examination.
A 22-gauge Quincke spinal needle is inserted 1.5 cm above the anus on the median line. The needle?s passage through the perineal planes is guided by TRUS. The needle is introduced posteriorly to the bulbar urethra up to the prostate apex and laterally to the membranous urethra. In this area, 2 mL of 1% mepivacaine are released. The needle is progressively retracted and 2-4 mL of anesthetic are administered along the needle path. An identical procedure is carried out on the other side through the same median hole.
The conventional technique performs biopsies by repeatedly inserting the same biopsy needle through the anaesthetized perineal plan.
In order to minimize the invasiveness of the technique, we proposed in 2003 an original technique using a coaxial 17-gauge needle (TruGuide Bard ? 13 cm long) . The coaxial needle is inserted up to the prostate apex through the anesthetized perineal path under TRUS guidance. On removal of the blunt tip stylet, the guiding cannula of the coaxial needle is an optimal transperineal path for the repeated atraumatic passage of the biopsy needle (18-gauge Tru-Cut, 20 cm long), loaded on a spring-driven biopsy gun (Magnum Bard Biopsy Instruments) with a cutting length of 22 mm.
The coaxial needle makes the procedure easier and quicker, allowing repeated introduction of the needle with low perineal trauma. The results of a prospective, randomised study comparing 51 patients undergoing conventional prostate transperineal biopsy and 51 patients undergoing transperineal prostatic biopsy using the coaxial needle showed a reduction of pain during the biopsy and a better compliance for patients using the coaxial needle .
Number and location of cores
The initial protocol at the Urology Department of Verona included 14 cores for each patient with a suspicion of prostate cancer. Six samples were performed in the peripheral zone according to the traditional ?sextant? scheme. Six additional cores were taken from the lateral portion of the peripheral zone. The last two biopsies regarded the transitional zone of each lobe.
According to the study protocol, each core was numbered and identified by site and prostatic lobe, so that the pathologist could report separate diagnoses for each core sent. This methodology allowed us to calculate the detection rate of different biopsy schemes, obtained by adding a pair of additional cores (from lateral peripheral gland or transitional zone) to the classical sextant scheme.
On analysing 480 patients with PSA values between 2.5 ng/ml and 20 ng/ml undergoing the first set of prostate biopsy, we found an overall prostate cancer detection rate of 43.8% . These results confirm those previously reported by other authors. In particular, Emiliozzi et al. reported a 51% prostate cancer detection rate with a transperineal double sextant biopsy in the peripheral zone .
In our study, the detection rate was significantly influenced by the presence or absence of prostatic anomalies at the digital rectal examination (DRE) and by prostate volume. Stratifying data for age and PSA Ł or >10 ng/ml, no significant differences were found. In detail, the detection rate proved to be 37.5% in patients with negative DRE and 56.7% in patients with positive DRE (p<0.0001).
According to prostate volume, the detection rate was 60.4% in patients with prostates Ł30 ml; 42.6% in patients with 30-50 ml prostates; and 24.2% in prostates >50 ml. The impact of DRE and prostate volume remained statistically significant at multivariate analysis.
The statistical comparison of the 14-core scheme detection rate with the other biopsy schemes, obtained by the exclusion of a pair of cores, enabled us to identify the ideal number of cores to be obtained according to prostate volume.
In particular, in Ł30 ml prostates the 14-cores scheme detection rate proved to be statistically overlapping with the 52.7% rate obtained with 8 cores (traditional sextant plus two additional cores at the prostatic apex). In 30.1-50 ml prostates, the 14-cores scheme detection rate overlapped the 40.6% rate obtained with the peripheral double sextant. In >50 ml prostates, the 14-cores scheme detection rate was considered insufficient to obtain an adequate sampling. These results, which were also confirmed after the exclusion of patients with positive DRE, persuaded us that the ideal number of cores for the first set of transperineal prostatic biopsy is 8 for prostates of less than 30 ml; 12 for 30-50 ml prostates; and more than 14 in patients with prostates >50 ml .
Currently, the data from our series and studies published in the literature do not allow us to exactly define the ideal number of cores to be taken in patients with prostate volume >50 ml.
Sending cores to the pathologist
To date, a core length of more than 10 mm is considered a quality indicator [14,15]. Shorter cores should be considered insufficient for a correct histological evaluation .
Core length depends on the features of the needle used, might be influenced by the biopsy site and is closely related to the core pre-embedding method [16-18].
The modality of core collection and embedding is a fundamental step in the biopsy procedure, as it can substantially influence the quality of the histological slides the pathologist will use to formulate the diagnosis.
The recommended technique to send cores to the pathologist is the so-called ?cassette? or ?sandwich? technique [17-19]. In our experience the core is transferred from the tru-cut needle onto a gauze soaked in an alcoholic solution. Then, the core is gently taken from one extremity with a delicate pinch and stretched onto an alcoholic wet nylon mesh, which is lodged in an apposite cassette. Each cassette contains a maximum of 3 cores, which lay covered by a second nylon mesh soaked in an alcoholic solution. The cassette is closed and dipped into 10% buffered formalin. Each individual core is identified with a numeric code giving its site (apex, intermediate portion and prostatic base; lateral apex, lateral intermediate portion and lateral prostatic base; transitional zone) and side (right and left) identification.
In another study, we analysed the features of transperineal prostate biopsy cores of 509 patients with the aim of verifying their correspondence to quality criteria and their relations with clinical and topographical parameters . Mean core length after transperineal prostate biopsy was 14 ?4.35 mm and all cores were >10 mm. The cores were fragmented in 3% of cases and the absence of prostatic tissue was reported only in 0.4% of cases. Core length did not show any correlation with patient age, PSA value, DRE and prostate volume.
The quality of the cores obtained through the transperineal approach might be considered similar to that of the transrectal cores. Data concerning the transrectal prostate biopsies performed during the Tyrol screening project show that the sandwich pre-embedded technique allowed authors to obtain a mean length of the positive cores of 13.17 mm . Similarly, in a multicentric American series analysing 1,847 patients who underwent transrectal prostate biopsy, mean core length was 12.8 ?3.5 mm . In the comparative study by Emioliozzi et al., the mean length of transrectal sextant cores was similar to that of transperineal sextant . Moreover, the transperineal approach seems to grant a more extensive sampling of the prostatic apex than of the intermediate or basal sites. Yet, these last two zones prove to be adequately sampled, with detection rates similar to those reported using the transrectal approach .
At the end of the procedure all patients receive an ice pack compressing the perineal zone for about 15 minutes. Thereafter, patients are observed until they pass urine. In the meanwhile, they are invited to fill up an institutional questionnaire to evaluate the pain experienced during the procedure. The quantitative evaluation of pain is performed using a visual/numeric scale (VAS/NAS) where ?0? indicates ?no pain?; a score between ?1? and ?4? indicates ?mild pain?; between ?5? and ?7? ?moderate pain?; and more than ?7? ?severe pain? .
In addition, at discharge all patients receive a form regarding the evaluation of complications, to be compiled during the following 30 days.
Of the 480 patients in our study who underwent prostate biopsy, the mean pain score was 2.1 ?1.4 (range 0-6). Among them, 90% reported mild pain and only 10% moderate pain. Acute urinary retention occurred in less than 1% of cases. Hospitalisation for complications was necessary in 1.2% of cases (3 cases of urinary tract infections with fever, 2 cases of severe hematuria, 1 patient with perineal haematoma) . Occasional hematuria and hemospermia were reported in 50 and 45% of patients, respectively.
Transperineal TRUS-guided prostate biopsy is a simple and tolerable procedure, with a low complication rate. The transperineal approach assures an optimal prostatic sampling, both for the peripheral and for the transitional zone. In particular, this access should grant a more extensive apical sampling than the transrectal approach, with similar core length in the intermediate and basal prostatic portions.
The literature data confirm a high detection rate in all categories of patients assessed. As regards the transrectal approach, the number of cores needed for an adequate prostatic sampling may vary according to prostate volume.
The morphometric features of the cores collected by means of transperineal biopsies perfectly satisfy the quality parameters necessary for an appropriate histological evaluation of the prostatic tissue.