Use of CT to reduce understaging in prostatic cancer: comparison with conventional staging techniques

The diagnostic accuracy of CT and MRI in the staging of pelvic lymph nodes in patients with prostate cancer: a meta-analysis

AIM

To compare the diagnostic accuracy of computed tomography (CT) and magnetic resonance imaging (MRI) in the diagnosis of lymph node metastases in prostate cancer.

METHODS

After a comprehensive literature search, studies were included that allowed construction of contingency tables for detection of lymph node metastases using CT or MRI. In addition, a summary receiver-operating characteristic (ROC) analysis was performed.

RESULTS

A total of 24 studies were included. For CT, pooled sensitivity was 0.42 (0.26-0.56 95% CI) and pooled specificity was 0.82 (0.8-0.83 95% CI). For MRI, the pooled sensitivity was 0.39 (0.22-0.56 95% CI) and pooled specificity was 0.82 (0.79-0.83 95% CI). The differences in performance of CT and MRI were not statistically significant.

CONCLUSION

CT and MRI demonstrate an equally poor performance in the detection of lymph node metastases from prostate cancer. Reliance on either CT or MRI will misrepresent the patient's true status regarding nodal metastases, and thus misdirect the therapeutic strategies offered to the patient.

BASELINE STAGING OF NEWLY DIAGNOSED PROSTATE CANCER: A SUMMARY OF THE LITERATURE

PURPOSE

Staging for prostate cancer often includes bone scanning and computerized tomography (CT). We systematically reviewed the published evidence for these tests.

MATERIALS AND METHODS

We searched MEDLINE for articles on these investigations in newly diagnosed cases of prostate cancer. Data were pooled based on prostate specific antigen (PSA), grade and tumor stage.

RESULTS

Among 23 studies examining the role of bone scan metastases were detected in 2.3%, 5.3% and 16.2% of patients with PSA levels less than 10, 10.1 to 19.9 and 20 to 49.9 ng/ml, respectively. Scanning detected metastases in 6.4% of men with organ confined cancer and 49.5% with locally advanced disease. Detection rates were 5.6% and 29.9% for Gleason scores 7 or less and 8 or greater, respectively. Among 25 studies CT documented lymphadenopathy in 0 and 1.1% of patients with PSA less than 20 and 20 ng/ml or greater, respectively. CT detection rate was 0.7% and 19.6% in patients with localized and locally advanced disease, respectively. Detection rates in patients with Gleason scores 7 or less and 8 or greater were 1.2% and 12.5%, respectively. These risks were typically much greater on pathological evaluation.

CONCLUSIONS

Patients with low risk prostate cancer are unlikely to have metastatic disease documented by bone scan or CT. Therefore, these investigations should not be standard practice. However, patients with PSA 20 ng/ml or greater, locally advanced disease, or Gleason score 8 or greater are at higher risk for bone metastases and should be considered for bone scan. CT may be useful in patients with locally advanced disease or Gleason score 8 or greater but appears not to be of benefit in patients with increased PSA alone.

MR imaging of pelvic lymph nodes

The occurrence of metastases to pelvic lymph nodes profoundly affects the prognosis of pelvic malignancies, making accurate staging crucial for selecting appropriate treatment. Modalities for the detection of metastatic lymph nodes are lymph node dissection, lymphangiography, and non-invasive techniques such as computed tomography (CT) and magnetic resonance imaging (MRI); the role of these techniques will be reviewed. Although this review will focus on prostate cancer, the statements may be generalised for other malignancies, as the metastases in pelvic lymph nodes have a similar pattern for other tumors.

Results of laparoscopic pelvic lymphadenectomy in patients at high risk for nodal metastases from prostate cancer

BACKGROUND

Laparoscopic pelvic lymphadenectomy (LPLND) can be performed safely and with minimal morbidity in the staging of prostate cancer. Its utility in evaluating patients at high risk for metastatic disease before primarily nonsurgical treatment modalities was evaluated.

METHODS

Twenty-four consecutive patients who underwent LPLND between June 1993 and July 1996 were studied. These patients were considered poor surgical candidates based on several risk factors, as follows: elevation of serum PSA >20 in 19 patients (79%); elevation of serum acid phosphatase in 4 patients (17%); digital rectal examination findings indicative of extraprostatic extension or seminal vesical involvement in 14 patients (58%); and poorly differentiated tumors on prostate biopsy in 19 patients (79%). Nineteen patients (79%) had two or more of these risk factors. Median PSA for the entire series of patients was 35.2 ng/mL (range 7.9 to 133 ng/mL), and median Gleason score was 7 (range 5 to 9). Preoperative CT or MRI was negative for pelvic lymph node metastases in 17 of 23 patients (79%), and bone scan was negative in all 24 patients.

RESULTS

Unilateral (n = 2) or bilateral (n = 22) LPLND was performed in all patients. Six patients (25%) had lymph node metastases detected laparoscopically. Five of the six patients had palpable extraprostatic extension (T3a/b) or invasion of a seminal vesical (T3c), and in four of these patients the site of the metastatic lymph nodes was ipsilateral to the palpable prostate abnormality. None of the risk factors was independently predictive of lymph node metastases within this series of patients. An average of 10.8 +/- 6.5 lymph nodes was removed at a mean operative time of 174 +/- 10 minutes for patients undergoing bilateral LPLND. Estimated blood loss was minimal for 20 of 22 patients (92%) undergoing LPLND alone, and there were no complications requiring open exploration. Mean postoperative hospital stay was 1.2 +/- 0.5 days for patients undergoing LPLND alone.

CONCLUSIONS

LPLND can be used efficiently to identify patients with nodal metastases from select high-risk patients. This, in turn, can exclude such patients from noncurative local and regional therapy.

A pharmacoeconomic evaluation of staging modalities for patients with newly diagnosed and occult recurrent adenocarcinoma of the prostate

Costs of staging prostate cancer using the Kit for the Preparation of Indium In111 capromab pendetide, a radiolabeled monoclonal antibody directed against prostate-specific membrane antigen, were evaluated using a medical decision model. Subjects were patients with newly diagnosed adenocarcinoma at risk for metastatic disease based on prostate specific antigen screening ≥10 and Gleason score ≥7, and occult recurrent disease. Information for the model was obtained from a meta-analysis of data from published medical literature, clinical trials, databases analysis, and expert opinion provided by an expert panel of five specialists in urology, surgery, radiation oncology, and nuclear medicine. When capromab pendetide, computed tomography, magnetic resonance imaging, and pelvic lymph node dissection were compared in patient with newly diagnosed or occult recurrent disease, capromab pendetide produced cost savings due to its ability to identify soft tissue lesions consistent with prostate cancer and to help establish the extent of disease.

Use of prostate-specific antigen, Gleason score, and digital rectal examination in staging patients with newly diagnosed prostate cancer

CT Scan, MR Imaging Scan, and Pedal Lymphangiography. Patients with a PSA greater than 25 ng/mL, a Gleason score greater than 6, and a positive DRE should undergo CT scan with FNA of lymph nodes at least 6 mm in size. Otherwise, CT scan, MR imaging scan, and pelvic lymphangiogram are not indicated. This should eliminate use of these staging studies in over 90% of patients with newly diagnosed adenocarcinoma of the prostate. Pelvic Lymph-Node Dissection. Pelvic lymph-node dissection can be safely eliminated in patients who meet the following predictive criteria: 1. PSA not more than 5 ng/mL or 2. Gleason score not more than 5 or 3. A combination of the following: PSA not more than 25 ng/mL, Gleason score not more than 7, and negative DRE. Following these criteria should eliminate the need for pelvic lymphadenectomy in 60% of patients with newly diagnosed prostate cancer.

Role of laparoscopic pelvic lymph node dissection in the management of patients with penile cancer and inguinal adenopathy

Patients with invasive squamous cell carcinoma of the penis and tumor involvement of the inguinal nodes are at risk for pelvic lymph node metastases. When this spread occurs, the chance for patient survival is limited. Because the sensitivity of CT in detecting pelvic lymph node metastases is low, open surgical pelvic lymphadenectomy is frequently performed. We have utilized laparoscopic pelvic lymphadenectomy as a minimally invasive alternative to this open approach in three patients with Stage T3 (UICC staging system) squamous cell carcinoma of the penis who had persistent inguinal adenopathy after a standard course of postpenectomy antiobiotic therapy. There were no intraoperative or postoperative complications, and all patients were discharged within 24 hours after surgery. The mean number of nodes removed was eight, and all specimens were free of tumor. Laparoscopic pelvic lymphadenectomy should be considered in patients with persistent inguinal adenopathy after antibiotic therapy before proceeding with inguinal lymph node dissection.

Patterns of lymphatic metastases at recurrence of prostate cancer: CT findings

We describe the CT patterns of lymphadenopathy and visceral metastasis in 22 men with clinical features of recurrent prostate cancer. Fifteen of 22 men (68%) had lymphadenopathy with predominant retroperitoneal disease in seven cases, a feature noted particularly in men whose primary treatment had involved radical pelvic radiotherapy. A previously unreported 'pseudolymphoma' pattern of massive retroperitoneal disease with contiguous invasion of the perirenal space and adrenal glands was seen (three cases). Whilst staging examinations with CT (or MRI) at initial diagnosis of prostate cancer may be confined to the pelvis if no pelvic lymphadenopathy is found, evaluation of suspected recurrent disease requires examination of the abdomen and pelvis. CT appearances of advanced prostate cancer may mimic retroperitoneal lymphoma.

Accuracy of combined computerized tomography and fine needle aspiration cytology in lymph node staging of localized prostatic carcinoma

The sensitivity and accuracy rate of computerized tomography (CT) in lymph node staging of localized prostatic carcinoma is commonly considered to be low. Fine needle aspiration cytology of pathological lymph nodes seen on radiological staging can enhance this low accuracy rate. We prospectively investigated the accuracy of CT and fine needle aspiration cytology in lymph node evaluation of 285 patients with clinically locally confined prostatic carcinoma. The sensitivity, specificity and accuracy rates of this combined method were 77.8%, 100% and 96.5%, respectively. False-negative staging results were found in only 10 patients with minimal nodal disease. Although in contrast with previous reports, combined CT and fine needle aspiration cytology in our hands seems to be a highly efficient staging method for lymph node involvement. This method could be considered as an alternative to surgical lymphadenectomy in the preoperative evaluation of the nodal status of patients with localized prostatic carcinoma who are scheduled for radical prostatectomy or curative radiotherapy.

Preoperative assessment of prostatic carcinoma by computerized tomography. Weaknesses and new perspectives

A retrospective study of five years' experience with fourth-generation computerized tomography (CT) scan was undertaken to assess the frequency of understaging in prostate cancer. A total of 160 patients with preoperative scans were surgically staged. In 10 patients, the operation was aborted after pelvic node dissection had revealed unsuspected metastatic involvement. Based on the histopathologic evidence of local tumor invasion, extension into seminal vesicles or pelvic lymph nodes, restaging was required in 78 percent of cases. Accuracy was 24 percent for capsular extension, 69 percent for seminal vesicle invasion, and 72 percent for lymphadenopathy. The poor yield of CT scan as a preoperative staging modality is demonstrated. Recent advances in the understanding and management of prostatic cancer require reassessing patient benefit and cost effectiveness of available imaging techniques, focusing on the problem of detecting nodal metastases, and predicting tumor spread to regional lymph nodes by accurately evaluating the primary neoplasm. We conclude that CT scan fails to demonstrate the required precision needed to evaluate local tumor spread; therefore, this goal must be pursued with newer imaging modalities.

Extraperitoneal pelvioscopy in lymph node staging of bladder and prostatic cancer

In view of the inadequate accuracy of radiological investigations, surgical lymphadenectomy is generally the last resort to assess lymph node involvement in bladder and prostatic cancers. Extraperitoneal pelvioscopy is a simple and effective method to avoid such invasive surgery, which is always slightly regrettable to perform purely for staging purposes. The investigation is performed with the patient under low spinal anesthesia via a short iliac incision using an instrument derived from the mediastinoscope. It allows biopsies from the external iliac, internal iliac, common iliac and obturator lymph node chains. We analyzed our results of pelvioscopy in 101 patients (36 prostatic and 65 bladder cancers). Extraperitoneal pelvioscopy, unilateral in 78 and bilateral in 23 cases, corrected the conclusions of the radiological assessment in 39% of the prostatic cancer cases and in 28% of the bladder cancer cases. The specificity and positive predictive value is 100%, sensitivity 84%, negative predictive value 93% and over-all reliability 95%. On the basis of the quality of the results and the low morbidity (5 cases of rapidly resolving lymphorrhea, 1 injury to the external iliac vein and 1 obturator nerve lesion), extraperitoneal pelvioscopy can be considered as a useful complement to the preoperative staging of bladder and prostatic cancer.

Transrectal ultrasonography in the staging of localized prostatic carcinoma. A pilot study

Transrectal ultrasonography (TRUS) was evaluated as a staging procedure in ten patients with localized prostatic carcinoma. The ultrasound images were correlated to histopathological whole-mount step sections of the surgical specimens after radical prostatectomy. Nine of the patients had pathological stage T3 (pT3) and only one was pT2. TRUS gave a diagnostic accuracy of 60% compared to 10% both for digital rectal examination (DRE) and computer tomography (CT) in detecting extracapsular tumor spread. We conclude so far that TRUS is superior to DRE and CT in detecting extracapsular tumor spread. Further we state that whole-mount step section of the surgical specimens is mandatory in order to achieve a correct pathological staging (pT-stage).

Normal variations of pelvic fat distribution implications on CT staging of pelvic tumors

In order to determine the normal variations of pelvic fat distribution, 25 men and 25 women normal pelvic computer tomography (CT) scans were reviewed. No distinct fat planes were demonstrated between the prostate and pelvic side walls, bladder and seminal vesicles, and prostate and rectum in 69%, 81%, and 86% of the men patients, respectively. Similarly, there were no distinct fat planes between the uterus and pelvic side walls, and uterus and rectum in 86% and 96% of the women patients, respectively. We conclude that there are no distinct fat planes around pelvic organs in the majority of normal people and this may be a major source of error in the CT staging of pelvic tumors.

Transrectal probe for 1H MRI and 31P MR spectroscopy of the prostate gland

A transrectal probe for 1H imaging and 31P MR spectroscopy of the prostate gland is described. The probe is covered with plastic and consists of an insectional portion containing an rf coil and a handle containing a tuning and matching circuit. Using this transrectal probe, 1H MR images and the first 31P MR spectra of the in situ canine prostate were obtained. Serial alterations in prostate size and changes in the ratio of phosphomonoesters to ATP ratio following orchiectomy were observed. Transrectal images of the prostate appear to be superior to conventional whole body coil images in the canine. For the first time a device to obtain high signal-to-noise 1H images and 31P spectra of the in situ prostate has been constructed. This will allow the assessment of transrectal imaging and spectroscopy as tools for medical studies of prostate pathophysiology.

Evaluation of prostate size: a comparison of ultrasound and magnetic resonance imaging

To determine the relative accuracy of ultrasonography (US) and magnetic resonance imaging (MRI) in the evaluation of prostate volume, we compared US and MR images with surgical findings in 15 patients. Transabdominal US was excellent for determining prostate size in patients with small to moderate enlargement. When compared with surgical specimens, the difference between the weight of the gland as predicted by US and the actual weight was 14% (SD +/- 12). With the transabdominal approach, the length was often inaccurately imaged, but the addition of transrectal scans in the sagittal projection improved results: with combined transabdominal and transrectal US, the average difference in weight was 8% (SD +/- 7). The MRI more accurately predicted prostatic volume (average difference, 6% (SD +/- 6), but the difference between the latter 2 is not significant. In 5 additional patients who had undergone transurethral resection of the prostate, residual prostatic tissue was evaluated by MRI and US. In addition to demonstrating prostate size, transrectal sagittal US showed the relationship among the bladder neck, prostatic urethra, and remaining prostatic tissue. Real-time US also allowed evaluation of dynamic sphincteric contractions, which is a finding not available today with MRI. Tissue differentiation was attempted with both MRI and US. Neither imaging modality could differentiate benign from malignant disease.

The value of computed tomography and ultrasound in assessment of pelvic lymph node metastases in patients with clinically locally confined carcinoma of the prostate

With the aim of detecting any metastases in pelvic lymph nodes, computed tomography (CT) was performed in 42 patients with clinically localized prostatic carcinoma, and ultrasound (US) examination in 35 of them, prior to pelvic lymphadenectomy. CT was positive in only one patient, and US was negative in all examined patients. At lymph node dissection macrometastases were found in four patients and histopathologic examination revealed micrometastases in a further ten patients. It is concluded that in clinically locally confined prostatic carcinoma CT and US are insensitive in diagnosing pelvic lymph node metastases, and that lymph node dissection remains the only method for staging of the regional lymph nodes.

The diagnostic significance of magnetic resonance imaging in prostatic tumours

Looking for better diagnostic methods of prostatic tumours the pelves of 38 males (22 of them suffering from prostatic carcinoma) were examined by magnetic resonance imaging (MRI). This new technique helps to distinguish between healthy and pathological prostatic tissue. It is a non-invasive method, which seems to gain improved significance in the preoperative delineation of prostatic cancer; it is a valuable tool for an accurate preoperative T-staging.

Staging of genitourinary cancers. The role of diagnostic imaging

Computed tomography (CT) is currently the standard modality for staging of urologic cancer in most institutions. It is used for demonstrating nodal involvement, and for demonstrating invasion of the primary lesion into surrounding fat, muscle, or other tissues or organs. It is also useful for demonstrating hepatic metastases in renal and vesical carcinomas. The problem with computed tomography, however, is that it can only show whether the nodes are large or not; neither can it show the nodal architecture, nor can it detect metastases in normal-sized nodes. Intravesical sonography has been helpful for staging papillary bladder cancer. Transrectal sonography has been somewhat helpful for demonstrating seminal vesicle invasion in patients with prostatic carcinoma. Inferior vena cavography and renal venography can be helpful for demonstrating whether a renal, renal pelvic, or adrenal carcinoma has extended into either vein. Lymphography can show nodal architecture and metastases in normal-sized nodes, and can make possible needle biopsy of abnormal-appearing nodes even if they are normal sized. The examination cannot show very small or microscopic nodal metastases, and it can miss abnormal nodes totally if they have been completely replaced by metastases. It yields false positives when fatty or fibrous infiltration of the nodes has occurred. It is used primarily for staging patients with testis or prostatic carcinoma. Bone scans are essential for staging prostatic carcinoma. Magnetic resonance imaging (MRI) is helpful in some cases of renal cell carcinoma. Multiplanar imaging prevents overstaging. It is also accurate for showing whether the renal vein or inferior vena cava are involved. Enlarged lymph nodes are easily distinguished from vessels. For staging bladder carcinoma involving the fundus or base of the bladder, MRI is better than CT. Microscopic nodal metastases, such as are common in carcinoma of the prostate, currently are not detected by any imaging modality.

Computerized tomography and transrectal ultrasound in the assessment of local extension of prostatic cancer before radical retropubic prostatectomy

The value of computerized tomography and transrectal ultrasound in the demonstration of local extension of prostatic cancer was evaluated in 38 patients undergoing radical retropubic prostatectomy. Transrectal ultrasound proved to be reliable for the demonstration of local extension of cancer beyond the prostatic capsule (sensitivity 86 per cent, specificity 94 per cent and accuracy 90 per cent). Invasion of the seminal vesicles was demonstrated by ultrasound, with a sensitivity of 29 per cent, specificity 100 per cent and accuracy 77 per cent. The addition of transrectal ultrasound scanning to clinical evaluation increased sensitivity in relation to detection of extraprostatic involvement from 15 to 92 per cent. When computerized tomography scanning was added to clinical examination, the sensitivity increased from 15 to only 46 per cent. Transrectal ultrasound is valuable for the preoperative evaluation of patients in whom radical prostatectomy is being considered as treatment for clinically localized prostatic cancer.

Echogenic structure of prostatic cancer imaged on radical prostatectomy specimens

Twenty radical prostatectomy specimens were scanned ultrasonically in vitro using a transrectal ultrasonic probe to evaluate the ultrasonic pattern of prostatic cancer. Histological and ultrasonic findings of the same areas were compared. No ultrasonic pattern specific for intracapsular prostatic cancer was found. Most often (in 40% of cases) the areas of prostatic cancer appeared hypoechoic on the ultrasonograms. In 30% of cases the carcinoma had a hyperechoic or mixed ultrasonic pattern, and in 30% the echo structure of the prostate was fairly uniform; intracapsular cancer could not be detected ultrasonically in these latter cases. The lack of a specific ultrasonic pattern for intracapsular prostatic carcinoma reduces the value of transrectal ultrasonography in detecting early intracapsular cancers. The main value of ultrasonography in patients with prostatic cancer is in the preoperative staging of the disease and in the follow-up of patients.

The role of CT in the staging and radiotherapy planning of prostatic tumours

Fifty patients with proven carcinoma of the prostate have been evaluated with CT. The CT studies were carried out for staging and radiotherapy planning and the findings compared with rectal examination and lymphography. CT provided useful additional information to that obtained by rectal examination in 40% of patients and these findings had important implications for radiotherapy planning. There was good correlation between CT and lymphography in the assessment of pelvic lymph node involvement.