Computergest�tzter transrektaler Ultraschall (C-TRUS) in der Diagnostik des Prostatakarzinoms

[Sonographic imaging of the prostate]

Accurate identification of the location of carcinoma in the prostate is essential for long-term therapeutic success, in particular for minimally invasive procedures. In recent years many new positive study results for prostate imaging have been reported which must be compared and evaluated and previous conservative assessments may need to be re-evaluated. In addition, combinations of different imaging techniques are increasingly being used in daily clinical routine. Due to technical advancements in sonographic imaging, such as elastography and contrast-enhanced ultrasound (CEUS), the detection rate of prostate cancer can be increased. An overview of the different imaging modalities and current literature are presented in this article.

New aspects in shear-wave elastography of prostate cancer

AIM

This study was designed to evaluate the performance of shear-wave elastography as a diagnostic tool for prostate cancer in a larger cohort of patients than previously reported.

PATIENTS AND METHODS

Seventy-three patients with suspected prostate carcinoma were investigated by ultrasound elastography followed by directed biopsy. The elastographic and histological results for all biopsies were compared.

RESULTS

After exclusion of invalid and non-assessable results, 794 samples were obtained for which both a histological assessment and an elastometric result (tissue stiffness in kPa) were available: according to the histology 589 were benign and 205 were malignant. Tissue elasticity was found to be weakly correlated with patient's age, PSA level and gland volume. ROC analysis showed that, for the set of results acquired, elastometry did not fulfil literature claims that it could identify malignant neoplasia with high sensitivity and specificity. However, it did show promise in distinguishing between Gleason scores ≤6 and >6 when malignancy had already been identified. Unexpected observations were the finding of a smaller proportion of tumours in the lateral regions of the prostate than generally expected, and also the observation that the elasticity of benign prostate tissue is region-sensitive, the tissue being stiffest in the basal region and more elastic at the apex.

CONCLUSIONS

Shear-wave elastography was found to be a poor predictor of malignancy, but for malignant lesions an elasticity cut-off of 80 kPa allowed a fairly reliable distinction between lesions with Gleason ≤6 and those with Gleason >6. We demonstrate an increase in elasticity of benign prostate tissue from the basal to the apical region.

[New puncture techniques in urology using 3D-assisted imaging]

The selective use of various puncture techniques for diagnostic or therapeutic purposes is a component of the daily routine of urologists. The aim of these interventions is always a safe and rapid puncture at the appropriate target point. Nowadays, imaging systems are increasingly being used in urology with the aim to achieve a more precise and safer planning and execution of punctures through an increased accuracy by the use of 3D representation. An approach to the solution to achieve this aim is the fusion of 3D reconstruction by magnetic resonance imaging (MRI) or computed tomography< (CT) with real-time imaging procedures, such as sonography or fluoroscopy.

[Multiparametric MRI, elastography, contrastenhanced TRUS. Are there indications with reliable diagnostic advantages before prostate biopsy?]

Prostate cancer (PCA) is the most common malignancy in men with an increasing incidence and is responsible for about 11,000 deaths per year in Germany. Fortunately, the mortality of PCA has decreased in recent years despite the rising incidence reflecting improvements in diagnostic methods. Many new innovations in imaging techniques for PCA are available and may be helpful in early detection of PCA. Contrast-enhanced sonography, computer-assisted sonography, elastography and multiparametric magnetic resonance imaging (MRI) seem to be the most promising methods to increase the detection rate of PCA during diagnostic work-up. The value of these new innovative techniques concerning improvement in PCA detection is reviewed.

Combination of C-TRUS with multiparametric MRI: potential for improving detection of prostate cancer

PURPOSE

To improve the detection of prostate cancer, especially in pre-biopsied patients, a guided biopsy based on radiologic findings is an option. We addressed the question, whether the combination of multiparametric MRI and computerized transrectal ultrasound (C-TRUS) improves the detection of prostate cancer.

METHODS

Twenty patients suspicious of having prostate cancer were included. Seventeen patients were pre-biopsied once or more. Each patient was examined by multiparametric MRI and C-TRUS, followed by a guided transrectal prostate biopsy series. Patients were stratified in a "low-risk" and "high-risk" group. The results were analyzed using descriptive statistics.

RESULTS

In 58 % (11 pat.) of patients, prostate cancer was found. In the "high-risk" group, biopsy in 73 % (8 pat.) of patients was positive for prostate cancer. All prostate cancer patients were found by C-TRUS-guided biopsies, whereas MRI did not reveal cancer in 27 %. 72 % (8 pat.) of patients had undergone radical prostatectomy. 65 % (6 pat.) had higher tumor stages after prostatectomy and 62.5 % (5 pat.) had higher Gleason-score.

CONCLUSIONS

Combination of multiparametric MRI and C-TRUS seems to improve detection of prostate cancer, especially in high-risk patients. Detection rates of C-TRUS in this study could confirm those of the primary C-TRUS studies. The benefit of MRI is the additional visualization of the tumor extension. The technique is an option for pre-biopsied patients. Both imaging methods often fail to predict correct tumor stage, but further studies are necessary.

[Influencing of the PSA concentration in serum by physical exercise (especially bicycle riding)]

BACKGROUND

Sports and in particular cycling are assumed to influence PSA in serum. Controversial scientific results were the motivation to examine the influence of a standardized test on a cycling ergometer and a treadmill on PSA concentrations in elderly men with elevated PSA levels and a benign prostate hyperplasia.

MATERIAL AND METHODS

A total of 21 male volunteers (aged 61 ± 5 years, tPSA 7.7 ± 3.0 ng/ml and benign prostate hyperplasia with a prostate volume of 54 ± 18 ml) performed a 1 h cycling test on a cycling ergometer. A subgroup of 15 volunteers also performed a 1 h test on a treadmill. Blood samples were drawn before and several times after the cycling stress test up to 7 days afterwards (up to 120 min after the test on the treadmill) to determine total PSA (tPSA), complexed PSA (cPSA) and free PSA (fPSA).

RESULTS

The average increase in tPSA of 1.9 ± 1.7 ng/ml (25%) after the cycling exercise test was significant. After the treadmill exercise the PSA increase was not as high, but with 1.0 ± 1.0 ng/ml (12%) was also significant. On average the levels of PSA returned to the basic level 48 h after the cycling test, but in individual cases it took longer. fPSA showed the most noticeable increase after cycling with 92% on average. There was no correlation between increase in PSA and prostate volume.

CONCLUSIONS

Men should abstain from physical exercise, especially from cycling for several days and at least for 24 h before PSA measurements are carried out. This applies to patients with elevated PSA levels (>4 ng/ml) when a PSA follow-up is being carried out.

[Core needle biopsy twice negative with rising PSA level. Does imaging help?]

In compliance with guidelines in cases of suspected prostate cancer, the standard approach involves transrectal ultrasound-guided systematic biopsies. Currently, according to the new S3 guideline for prostate cancer, 10-12 tissue samples should be collected per patient and session. If these primary specimens are negative, the number of multiple biopsies is generally increased in the second session to improve the diagnostic certainty with more biopsies. At the latest when the second core needle biopsy is performed in the presence of rising prostate-specific antigen (PSA) level, an attempt is made to minimize the risk of overlooking prostate cancer by further increasing the number of multiple biopsies in the sense of achieving saturation. In this instance, the number ranges from 6 to 143 tissue samples per session. Studies have provided evidence that after two systematic random biopsies the same number of additional random biopsies does not accomplish any essential improvement of diagnostic certainty. There are hardly any studies in the literature dealing with the role of imaging procedures after negative prostate biopsies. In a prospective clinical trial including 132 patients with an average of 12 negative previous biopsies, a dramatically high number of prostate carcinomas (66 of 132) could be detected with innovative imaging (1-6 targeted biopsies). This raises the question of how reliably multiple systematic biopsies can in fact exclude the presence of cancer. Thus, particularly after a negative series of multiple biopsies, it appears to be expedient to use specific imaging to enhance diagnostic certainty through quality. However, prospective clinical validation of the diverse innovative methods seems to be important before broad application.

A multi-classifier system for the characterization of normal, infectious, and cancerous prostate tissues employing transrectal ultrasound images

A computer-aided diagnostic system has been developed for the discrimination of normal, infectious and cancer prostate tissues based on texture analysis of transrectal ultrasound images. The proposed system has been designed using a panel of three classifiers, which have been evaluated individually or as a mutli-classifier scheme, using the external cross-validation procedure. Clinical data consisted of 165 transrectal ultrasound images, characterized by an experienced physician as normal (55/165), cancerous (55/165), and infectious (55/165) prostate cases. From each image, the physician delineated the most representative regions of interest, from which, 23 textural features were extracted. Classification was seen as a two level hierarchical decision tree. Normal from infectious and infectious from cancer cases were discriminated at the 1st and 2nd level of the decision tree, respectively. The best classification results for the 1st level were 89.5%, whereas for the 2nd level 90.1%. The utilization of multi-classifier system improved the discrimination of prostate pathologies as compared to individual classifiers; for infectious prostate cases improvement was from 87.3% to 88.7% and for cancer prostate cases improvement was from 84.1% to 91.4%. In terms of overall system performance (the decision tree's node propagating error taken into account), best classification accuracies were 89.5%, 79.6% and 82.7% for the recognition of normal, infectious and cancer cases, respectively. The proposed system might be used as a second opinion tool for assisting diagnosis of different prostate pathologies.

Transrectal contrast enhanced ultrasound for diagnosis of prostate cancer

The diagnosis of prostate cancer is based on histology. Prostate biopsies are obtained based on the triad of prostate specific antigen (PSA), digital rectal examination (DRE) and transrectal ultrasound. Because prostate biopsies still have a large percentage of negative outcomes, patient selection and biopsy direction need improvement. This paper describes the recent improvements in prostate cancer imaging, especially contrast-enhanced transrectal ultrasound.

Urologic imaging for localized prostate cancer in 2007

Increasing numbers of systematic random biopsies have virtually replaced urologic imaging as a detection and staging tool in prostate cancer. TRUS as the most commonly utilized urologic imaging is now mainly utilized to guide the biopsy needle into the correct anatomical or topographic region of the prostate. But even multiple systematic random biopsies have been shown to overlook a large number of clinically significant carcinoma. This fact has led to a dramatic increase in the number of biopsies taken in the detection of localized prostate cancer. There are some centers where 6, 10, 12, even up to 143 biopsies are taken in one sitting. This increasingly invasive and heterogeneous strategy underlines the need for an improvement in diagnostic imaging. New modalities and innovative techniques are currently being investigated in order to identify prostate cancer more accurately. The purpose of this paper is to review innovative urologic imaging techniques to identify emerging modalities that may be beneficial in the management of prostate cancer. Enhanced transrectal ultrasonography modalities, including ultrasound contrast agents, color and power doppler, elastography and computerized (C)-TRUS with artificial neural network analysis (ANNA) promise benefits in comparison to standard gray-scale ultrasonography to accurately target and diagnose prostate cancer.

Bilder in der Urologie: Faszination und Perspektiven

In contrast to other countries (e.g., USA) the German urologist routinely utilizes imaging in order to evaluate urological disorders. Ultrasound as a basic tool has acquired importance similar to the physical examination or the patient history. Because of its minimal invasiveness and low cost, it is increasingly utilized as a first-line exam.In correlation with the patient history and laboratory data more invasive imaging studies are performed and in unclear cases or in the preoperative work-up more extensive imaging procedures like computed tomography (CT) or magnetic resonance imaging (MRI) are utilized. Even in emergency situations the urologist is able to guide interventions under ultrasound or conventional X-ray guidance (e.g., percutaneous drainage of dilated kidney), which resulted in a much lower complication rate of the various procedures. In those cases in which ultrasound is technically infeasible or in unclear cases CT and MRI are used as problem-solving procedures and are able to give the correct diagnosis in a large percentage of cases.After a brief historical overview, newer modalities and innovative techniques are explored and presented. Assuming that these innovative approaches lead to more accurate diagnosis and staging of various neoplastic and nonneoplastic conditions, treatment can be performed in earlier stages of diseases and better stage-adapted treatment can be offered to the patients.

[Innovative approaches in prostate cancer ultrasound]

Today, systematic random biopsies have virtually replaced ultrasound as an imaging tool in the early diagnosis and staging of prostate cancer. Transrectal ultrasonography (TRUS) is now utilized almost only to guide the biopsy needle into the correct anatomical or topographical region of the prostate. Nevertheless, a large number of clinically significant carcinomas are not discovered despite of multiple systematic biopsies. This has led to a dramatic increase in the number of biopsy samples taken, with 6, 10, 12 to 143 being taken during one session depending on the site. Newer modalities and innovative techniques are being investigated in order to accurately identify patients with prostate cancer at different stages of the disease. Innovative ultrasonography techniques may improve the diagnosis and staging of current imaging techniques.

Innovative Diagnostik in der Früherkennung und beim Staging des lokalisierten Prostatakarzinoms

Prostate cancer is the most common malignancy in males. Men aged 50 years and older are recommended to undergo an annual digital rectal examination (DRE) and determination of prostate-specific antigen (PSA) in serum for early detection. Fortunately, disease-specific mortality continues to decline as a result of advances in screening, staging, and patient awareness. However, about 30% of men with a clinically organ-confined disease show evidence of extracapsular extension or seminal vesicle invasion on pathological analysis. Consequently, there is a need for more accurate diagnostic tools for planning tailored treatment. A variety of modern imaging techniques has been implemented in an attempt to obtain more precise staging, thereby allowing for more detailed counseling, and instituting optimum therapy. This review highlights developments in prostate cancer imaging that may improve staging and treatment planning for prostate cancer patients.