Prostatic Ultrasound and Needle Biopsy

Prostate cancer is now the most common malignancy in men, both in the United States and in Europe. Approximately 97% of all prostate cancers are adenocarcinoma. Other histologic types include neuroendocrine tumors, sarcoma, carcinoid tumors, melanoma, and metastases to the prostate. Both the morbidity and mortality from prostate cancer are increasing. Whether this is a true finding or just a result of a longer life expectancy and improved technology for early diagnosis is still debated.

DIAGNOSIS

Until the development of transrectal ultrasound (TRUS) of the prostate and of detection methods for prostate-specific antigen (PSA), the digital rectal examination (DRE) was the primary tool in the clinical diagnosis of prostate cancer. Likewise, the histologic diagnosis, indispensable for further management of the disease, has evolved from “blind” finger-guided punctures with a Tru-Cut needle to a procedure of refined echo-guided tissue sampling. The almost simultaneous introduction of a spring-driven “biopsy gun” (Biopty) was an invaluable adjunct to this technique.

INDICATIONS FOR SURGERY

Obtaining a histologic diagnosis of prostate cancer should be the goal whenever this opens therapeutic prospects for patients, but only then. In other words, the suspicion of prostatic malignancy in a man with a limited life expectancy for any reason other then prostate cancer should not automatically lead to any prostatic biopsy procedure. Assuming a reasonable life expectancy, however, the indications for TRUS are either an elevated PSA (actual or age adjusted) or abnormal DRE with any level of PSA. Transrectal ultrasound-guided biopsy is also appropriate in an older man with a limited life expectancy who has obstructive or irritative voiding symptoms. Such a patient may benefit from palliative treatment of a prostate cancer. In addition to securing the diagnosis, TRUS can be used to assist in the collection of directed biopsies from selected areas in and around the prostate, which will assist in staging the disease.

ALTERNATIVE THERAPY

Among the available and generally accepted methods to collect prostate tissue for histologic diagnosis, the transrectal ultrasound-guided biopsy with the “biopsy gun” has become the most popular one over the last years. Blind, digitally guided prostatic biopsies can be done with the same biopsy gun, but they are less accurate, especially for the diagnosis of small, nonpalpable lesions. Transperineal echo-guided biopsies are too laborious and thus reserved for patients in whom the rectal access is impossible. In selected patients the diagnosis is made, sometimes unexpectedly, on histologic examination of tissue material obtained after transurethral prostatic resection.

SURGICAL TECHNIQUE

Although transrectal ultrasound-guided biopsy of the prostate is an outpatient procedure, some precautionary measures and preparations are recommended in order to optimize its accuracy and to minimize complications.

Precautions

Whenever a urinary tract infection might be present, a urinary sample for cytobacteriologic examination should be collected, and eventual infections should be treated adequately. Patients with acquired or iatrogenic coagulation disorders should be, when judged reasonable, medically accommodated with styptics or by temporarily interrupting their anticoagulation treatment. Though infrequently necessary, it is occasionally appropriate to provide some tranquilizing or analgesic drug to very anxious patients.

Preparations

Preoperative cleansing enemas the evening before and the morning of the procedure empty the rectal ampulla of gas and feces, optimizing the visualization. Antibiotic prophylaxis is given empirically, generally a fluoroquinolone the morning of the procedure, followed by a full dose of the fluoroquinolone for 3 days.

Biopsy Technique

The patient is placed on a comfortable examination table, in left lateral decubitus position, knees flexed toward the chest. The examiner takes his or her place on a stool on the right side of the patient and explores the rectal ampulla and the posterior aspect of the prostate with an index finger. The gloved and lubricated finger palpates for gross abnormalities and prepares the patient’s anus for the introduction of the ultrasound probe.

The ultrasound equipment should generate high-frequency (7 to 10 MHz) multiplane images of the prostate. If the probe works with an external needle guide, the guide should be fixed to the probe before its introduction. Internal needle guides can be added with the probe in position. Some probes have an optional small balloon on top, to be filled with water, for better visualization. Even though this balloon will probably be pierced by the biopsy needle, its use is recommended for optimal initial examination of the prostate and seminal vesicles. A condom, filled with some jelly inside, is pulled over the distal part of the probe. After lubrication of the top of this condom, the probe is ready for introduction.

Depending on the other clinical findings (DRE, PSA, previous TRUS), the prostate is first scrutinized for abnormalities. Taking into account possible rebiopsies in case of a negative result, it is good policy to note the DRE and TRUS findings at this time. Especially of interest are the volume of the prostate, the presence of hypoechoic lesions, asymmetries, and discontinuities of the prostate boundary echo. When the biopsies return with a positive result, these data will certainly be helpful in the further management of the disease.

An 18-gauge Tru-Cut biopsy needle is placed in the mechanical actuating device (Biopty or alternative system). Before this device is introduced through the hollow needle guide, the ultrarapid discharge of the gun is checked to ensure the functioning of the system and to accustom the patient to this surprising sound.

The targets in the prostate are now localized by moving the probe in the rectum and switching between the axial and sagittal planes. A little trick to prevent downsliding of the needle along the capsule of the prostate at the time of the biopsy itself is to turn the oblique face of the top of the needle away from the patient.

If the only goal is to know whether an ultrasonically hypoechoic lesion is malignant or not, two or three directed tissue samples of this lesion should be enough. The lesion is brought into view in the sagittal plane, meaning that it is crossed by the electronic puncture line, and the needle is advanced in the guide until its hyperechoic tip is clearly seen at the edge of the lesion.

A gentle warning is addressed to the patient, and the needle is fired off into the lesion. One can easily judge the accuracy of the biopsy, as it is done in real time, and the moving needle creates a very strong reflection along its biopsy course. Even after an apparently perfectly directed biopsy, it is always recommended to take at least one extra core. In a patient who might be a candidate for curative treatment, it is also necessary to collect at least three tissue cores from the contralateral side (see sextant biopsies).

If an indurated prostatic nodule is palpated but not recognized on TRUS, geographic biopsies are indicated. The site of the suspicious lesion, i.e., left or right side, apex to base, is noted, and the biopsies are guided in that region of the prostate. Three additional biopsies from the contralateral side are again the standard.

In patients with suspicion of prostate cancer (elevated PSA) but without palpable or echogenic abnormalities, we recommend the performance of “sextant biopsies”. These biopsies are directed to the lateral margins of the peripheral zone of the prostate, where the majority of cancers originate. On each side three biopsies are taken: one at the apex, one at the base, and one in between. Here, the puncture needle should be advanced until its tip lies just in front of the prostatic capsule. That way one is sure to obtain representative tissue cores of 15 mm. If the “sextant biopsies” return negative from the pathology department and cancer suspicion persists, one can either repeat the procedure or extend it into the transectional zone of the prostate. We do not perform these biopsies routinely as they are far more invasive and painful.

OUTCOMES

Complications

In most cases the postbiopsy period is free of complications, but the patient is always told of possible adverse events. There might be some rectal bleeding, which is usually taken care of with a clean absorbing cloth. Exceptionally an internal rolled lubricated bandage is placed and can be safely removed at home after a couple of hours. Hematuria resulting from a urethral injury can occur, even several days after the procedure. Hemospermia, a benign and predictable event after a prostate biopsy, can frighten the patient, even weeks later.

The patient is always warned of the possibility of high fever or chills and is asked to seek immediate medical help in this event. Again, this is an exceptional complication, certainly after antibiotic prophylaxis.

Results

In Cooner’s 1990 study of the role of transrectal ultrasound, his overall detection rate was 14% for all patients undergoing biopsy. He performed a biopsy only on those patients with a visible hypoechoic lesion. The detection rate increased with increasing PSA: 4.5% of patients with a PSA < 4.0 ng/ml had a hypoechoic lesion with a positive biopsy; 17% of patients with a PSA > 4.0 ng/ml but < 10.0 ng/ml had a positive biopsy; 53% of patients with a PSA > 10 ng/ml had a positive biopsy. Cooner’s detection rate for transrectal ultrasound-guided biopsy in patients with a PSA > 4.0 ng/ml was 33%. Vallancien reported a detection rate of 26% with systematic sextant biopsies in men with a PSA > 4.0 ng/ml and a normal DRE.6 Smith reported a detection rate of 29% at the initial evaluation of men with PSA > 4.0 ng/ml and an overall detection rate of 45% when these same men were followed longitudinally and evaluated with repeat biopsies.

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: