Endoscopic ultrasound in the pre-operative staging of rectal carcinoma

Results of EUS in detecting perirectal lymph node metastases of rectal cancer: the pathologist makes the difference

BACKGROUND

Accurate preoperative staging of primary rectal cancer is mandatory because the result may affect therapeutic decisions. Endoscopic ultrasonography (EUS) is considered the most accurate method for locoregional staging, but the issue of possible variations in the assessment of its accuracy related to technical aspects of pathologic staging has never been raised. The aim of this study was to assess EUS results as determined by two different methods of dissection of surgical specimens.

METHODS

Among all cases with primary rectal cancer staged with EUS from April 1991 to April 1997, 131 patients underwent surgery without preoperative radiotherapy; EUS results for nodal staging were compared with those obtained by pathology. Resected specimens were examined using two different techniques (conventional vs. special dissection).

RESULTS

There was a significant decrease in diagnostic accuracy of EUS according to pathologic technique. Overall accuracy, sensitivity, specificity, positive and negative predictive values for conventional versus special dissection were as follows: 74.6% vs. 43. 3% (p = 0.0001), 67.8% vs. 21.8% (p = 0.0002), 79.1% vs. 67.8% (p = 0.14), 67.8% vs. 43.7% ( p = 0.02), and 79.1% vs. 43.2% (p = 0.0003), respectively. EUS sensitivity according to size of metastatic lymph nodes was significantly lower for nodes smaller than 5 mm in diameter (p = 0.025) when special dissection was performed because of a larger number of lymph nodes harvested.

CONCLUSIONS

Our findings raise concern about the results of EUS staging of lymph node metastases in rectal cancer. Further prospective studies on a node-by-node basis could clarify the real diagnostic yield of EUS.

Radiologic staging of gastrointestinal cancer

Pre-operative staging should define the probable course of a patient's disease, separate the resectable from the unresectable patients, and identify the patients who are candidates for induction therapy. Pre-operative staging must be well tolerated and should provide new or important information that will affect the proposed treatment plan. For some diseases such as colon cancer, pre-operative staging is largely unnecessary, but it can be of great value for other tumors such as pancreatic cancer. Currently, many imaging techniques are available to evaluate gastrointestinal cancers, and each provides information necessary for directing treatment. Although no individual technique can stage patients with complete accuracy, combinations of the various imaging techniques can be used to increase accuracy and promote appropriate decisions about an individual's treatment options. The use of current imaging techniques for staging primary lesions, regional spread, and the intra-abdominal metastatic spread of the most common gastrointestinal malignancies are reviewed.

Colon cancer during pregnancy. The gastroenterologist's perspective

Colon cancer during pregnancy is uncommon but not rare, with an estimated incidence of several hundred cases per year in the United States. This type of cancer tends to have a poor prognosis that is attributable to delays in diagnosis and advanced disease at diagnosis. The diagnosis frequently is delayed because symptoms of colon cancer, such as rectal bleeding, nausea and vomiting, and constipation, often are attributed to normal pregnancy or minor complications of pregnancy. Pregnancy affects the diagnostic evaluation and therapy of colon cancer because of fetal risks of diagnostic tests and therapy. Appropriate medical evaluation of significant lower gastrointestinal complaints during pregnancy can lead to an earlier and improved diagnosis.

Limitations and pitfalls of transrectal ultrasonography for staging of rectal cancer

PURPOSE

This study was designed to evaluate the accuracy of preoperative staging by transrectal ultrasonography (TRUS) and to clarify the limitations and pitfalls of TRUS by clinicopathologic analysis for staging errors.

MATERIALS AND METHODS

Results of TRUS for 164 consecutive patients with rectal cancer were compared prospectively with histopathologic findings according to the newest TNM classification. Clinicopathologic factors that may influence staging errors were analyzed by reviewing both resected specimens and hard copies of TRUS.

RESULTS

There were 13 patients histopathologically staged as pTis, 21 as pT1, 34 as pT2, 84 as pT3, 12 as pT4, 73 as pN0, and 91 as pN1-3. Of these, 85, 86, 56, 93, 75, 74, and 77 percent, respectively, were correctly staged by TRUS. Excluding 12 cases with incomplete examinations because of annular constricting tumors, overstaging of tumor invasion depth was mostly caused by tumor invasion close to the deeper uninvolved layer, inflammatory cell aggregation, desmoplastic change, and hypervascularity around the tumor, mimicking tumor invasion on TRUS. The understaging was mostly the result of microscopic invasion beyond the estimated layers and difficulties in examination because of the tumor location being close to the anal canal or on the Houston's valves or the tumor shapes being polypoid or bulky and fungating. Overstaging in lymph node status was caused by reactive lymph node swelling and understaging by the presence of only small involved node and metastasis in the extramesorectal nodes.

CONCLUSIONS

An awareness of the limitations and pitfalls of TRUS, as demonstrated by the present study, should improve staging accuracy and contribute to optimum clinical decision-making.

Endosonography for preoperative staging of rectal tumours

PURPOSE

The aim of this study was to evaluate the use of rectal endosonography for preoperative staging of tumour extension and lymph node involvement in rectal tumours.

MATERIAL AND METHODS

Over a 4-year period 100 patients with rectal tumours were studied with sonography using 7 MHz endoprobes. Tumour spread was assessed according to the TNM classification, and the number and maximum size of perirectal lymph nodes were registered. The sonographic findings were compared with the surgical and histological findings.

RESULTS

The overall accuracy of endosonography in assessing local tumour extension was 85% (76-91%; 95 percent confidence limits). T4 tumours with a large contact surface to an adjacent organ tended to be nonresectable. Lymph node assessment could be made in 81 patients who underwent radical resection: sonography showed lymph nodes in 49 patients, 30 of whom had nodal metastases; the histological examination showed lymph nodes in the remaining 32 patients, 8 of whom had nodal metastases. The number of lymph nodes at the histological examination was markedly higher than the number depicted by preoperative ultrasound.

CONCLUSION

This study confirmed the use of endoluminal ultrasound in the preoperative evaluation of local tumour spread. However, endosonographic assessment of perirectal nodal involvement seems to be too unreliable to be used for the preoperative selection of patients.

Efficacy of high-frequency ultrasound probes for the preoperative staging of invasion depth in flat and depressed colorectal tumors

BACKGROUND

Flat and depressed nonpolypoid types of colorectal tumors have drawn much attention. Since endoscopic mucosal resection technique is available, it is of great importance to distinguish intramucosal carcinoma from invasive carcinoma because determination of the invasion depth is essential for choosing this therapy. The usefulness of high-frequency (20 MHz) ultrasound probes for preoperative staging of invasion depth in this type of colorectal tumor was evaluated.

METHODS

Forty-nine cases of flat and depressed tumors were examined with the ultrasound probe and diagnostic accuracy was confirmed by comparing ultrasonic images with the pathologic findings of the specimens resected either by endoscopic mucosal resection or surgical operation.

RESULTS

The normal colonic wall was visualized as a nine-layered structure and the muscularis mucosae was depicted in 37 (76%) of 49 cases. Flat and depressed tumors were visualized as hypoechoic lesions and the invasion depth was accurately diagnosed in 43 (88%) of 49 lesions.

CONCLUSIONS

High-frequency ultrasound probes proved to be useful in determining the invasion depth and therapeutic strategy in flat and depressed colorectal tumors.

Three-dimensional endorectal ultrasonography for staging of obstructing rectal cancer

PURPOSE

Preoperative staging of advanced carcinoma of the rectum by conventional endorectal ultrasonography is often impossible because of the presence of obstruction, which does not allow passage of the endoprobe. In a prospective study, we investigated the value of three-dimensional endorectal ultrasonography for staging of obstructing rectal cancer. This technique permits examination of obstructing rectal tumors because scan planes can be chosen deliberately within a scanned volume.

METHODS

Overall obstructing tumors not accessible for conventional endoprobes were found in 26 of 94 patients who were subjected to endorectal ultrasonography for staging of rectal cancer. Three-dimensional volume scanning was performed using a three-dimensional frontfire transducer or a three-dimensional bifocal multiplane transducer (7.5/10 MHz). Data of the three-dimensional scans were stored on a hard disk for subsequent evaluation with a combison 530 processor.

RESULTS

Three-dimensional transrectal endosonography enabled visualization of local tumor spread in all 26 patients. In 18 patients, obstruction was caused by advanced primary rectal carcinoma. Endosonography accurately determined the tumor infiltration depth in three T2 tumors, eight T3 tumors, and three T4 tumors. Overall accuracy for assessment of infiltration depth was 78 percent. Accuracy for assessment of perirectal lymph node involvement was 75 percent. In eight patients, the obstruction was attributable to extramural regrowth of rectal cancer after surgery. Diameter of the lesions ranged between 3 and 6 cm. Although all lesions were clearly depicted by three-dimensional endosonography, only five lesions (62 percent) were detected by computed tomography.

CONCLUSIONS

Three-dimensional endorectal ultrasonography provides previously unattainable scan planes and enables accurate staging of obstructing rectal tumors. This technique may improve therapy planning in advanced rectal cancer by selecting patients who require preoperative adjuvant therapy.

Endoscopic assessment of invasion of colorectal tumors with a new high-frequency ultrasound probe

The present study was carried out to clarify the usefulness of and problems associated with a new ultrasound probe in the assessment of invasion of colorectal tumors. Normal colorectal wall of 23 resected specimens from colorectal cancer cases was examined in vitro with the probe. Fifty-one patients with colorectal carcinoma and 16 patients with rectal carcinoid tumor were presurgically examined using the probe via the biopsy channel of a conventional colonoscope. After endoscopic and ultrasonographic examination, 27 patients underwent endoscopic resection and 40 underwent surgical resection. The ultrasonographic findings were compared with histologic findings in all cases. Carcinomas and carcinoid tumors were visualized as an echo-poor region with the probe. The overall accuracy rate for depth of invasion was 76% (39/51) for colorectal cancer. The accuracy rates for tumors limited to the mucosa and tumors invading the submucosa were 83% and 90%, respectively; these rates were higher than those for tumors invading the muscularis propria (50%) and beyond the muscularis propria (73%). In all 16 cases of carcinoid tumor, the depth of invasion was accurately shown to be limited to the submucosa. This probe is useful to assess invasion of colorectal tumors, especially small and flat lesions limited to the mucosa or submucosa.

Transrectal and transvaginal ultrasonography in the preoperative staging of rectal carcinoma

To evaluate the diagnostic ability of transrectal and transvaginal ultrasonography (TRUS and TVUS), 132 patients with rectal carcinoma were examined. Analysis of the data obtained has shown that the high quality of endosonographic imaging allows the performance of detailed staging of rectal carcinoma. In the great majority of patients (91%) the staging was carried out correctly. Neoplastic invasion was overstaged in only five cases and understaged in another five cases. Altered pararectal lymph nodes could be visualized by endosonographic examination in 54.5% of patients.

Transrectal ultrasound of rectal tumors

Since preoperative staging of rectal tumors is important in planning treatment, we evaluated transrectal ultrasound (TRUS) staging of rectal neoplasms. In 35 consecutive rectal tumors, we compared TRUS staging results with final pathologic staging. TRUS predicted the degree of tumor invasion in 19 of 24 patients (79%) and the presence or absence of lymph node metastasis in 11 of 15 patients (73%). TRUS overestimated the degree of tumor invasion in four patients (17%) and underestimated invasion in one patient (4%). The depth of tumor invasion was correctly predicted in all 14 tumors located within 6 cm from the anal verge, but, beyond 6 cm, only 5 of 10 tumors (50%) were staged correctly (p = 0.005). In the group of 11 patients who underwent preoperative radiotherapy, pretreatment TRUS predicted the depth of tumor invasion in only six patients (55%) and overestimated tumor invasion in five patients (45%), suggesting that nearly half of these tumors were downstaged by radiotherapy. TRUS accurately predicts the degree of tumor invasion, especially in tumors closer to the anal verge, allowing for better treatment planning in patients with low to middle rectal neoplasms.

Radiology and endoscopy in the pretreatment diagnostic management of colorectal cancer

This paper discusses the imaging methods available for the detection and diagnosis of colon cancer, concentrating on endoscopy and barium radiology. Effective utilization of these two methods may be facilitated by using flexible sigmoidoscopy to direct further investigation. There is a need for educational efforts to enhance the performance of endoscopy and barium radiology so that the high standards achieved in some published series are more generally available to patients. New developments in contrast agents will alter rapidly the roles of ultrasound, CT scanning, and magnetic resonance in the investigation and management of colorectal cancer.