Preoperative staging of rectal cancer using a 7.5 MHz front-loading US probe

Imaging assessment of early rectal cancer

Early rectal cancer (ERC) is defined as invasive adenocarcinoma spreading into, but not beyond, the submucosa or muscularis propria-that is a Dukes'A: T1N0 or T2N0 tumour in the tumour node metastasis (TNM) classification (Taylor et al. 2008). Among these tumours it is suggested that the most superficial T1 tumours least likely to metastasize to local lymph nodes than adenocarcinoma invading deeper where the rich lymphatic and venous plexuses within the submucosa provide a mechanism for tumour spread beyond the rectum. Currently, only about 10 % of patients presenting symptomatically with rectal cancer are diagnosed with early disease; however, up to 30 % of screen detected cancers are being identified as Dukes'A. Thus, the overall detection of early stage tumours is likely to increase following greater implementation in screening programs. The goal of this invited review is to provide recommendations based on the consensus discussion on the information from preoperative imaging that is of relevance for clinical decision-making for patients with early rectal cancer.

Transrectal ultrasound and magnetic resonance imaging measurement of extramural tumor spread in rectal cancer

AIM: To evaluate the agreement between transrectal ultrasound (TRUS) and magnetic resonance imaging (MRI) in classification of ≥ T3 rectal tumors.

METHODS: From January 2010 to January 2012, 86 consecutive patients with ≥ T3 tumors were included in this study. The mean age of the patients was 66.4 years (range: 26-91 years). The tumors were all ≥ T3 on TRUS. The sub-classification was defined by the penetration of the rectal wall: a: 0 to 1 mm; b: 1-5 mm; c: 6-15; d: > 15 mm. Early tumors as ab (≤ 5 mm) and advanced tumors as cd (> 5 mm). All patients underwent TRUS using a 6.5 MHz transrectal transducer. The MRI was performed with a 1.5 T Philips unit. The TRUS findings were blinded to the radiologist performing the interpretation of the MRI images and measuring the depth of extramural tumor spread.

RESULTS: TRUS found 51 patients to have an early ≥ T3 tumors and 35 to have an advanced tumor, whereas MRI categorized 48 as early ≥ T3 tumors and 38 as advanced tumors. No patients with tumors classified as advanced by TRUS were found to be early on MRI. The kappa value in classifying early versus advanced T3 rectal tumors was 0.93 (95% CI: 0.85-1.00). We found a kappa value of 0.74 (95% CI: 0.63-0.86) for the total sub-classification between the two methods. The mean maximal tumor outgrowth measured by TRUS, 5.5 mm ± 5.63 mm and on MRI, 6.3 mm ± 6.18 mm, P = 0.004. In 19 of the 86 patients the following CT scan or surgery revealed distant metastases; of the 51 patients in the ultrasound ab group three (5.9%) had metastases, whereas 16 (45.7%) of 35 in the cd group harbored distant metastases, P = 0.00002. The odds ratio of having distant metastases in the ultrasound cd group compared to the ab group was 13.5 (95% CI: 3.5-51.6), P = 0.00002. The mean maximal ultrasound measured outgrowth was 4.3 mm (95% CI: 3.2-5.5 mm) in patients without distant metastases, while the mean maximal outgrowth was 9.5 mm (95% CI: 6.2-12.8 mm) in the patients with metastases, P = 0.00004. Using the MRI classification three (6.3%) of 48 in the MRI ab group had distant metastases, while 16 (42.1%) of the 38 in the MRI cd group, P = 0.00004. The MRI odds ratio was 10.9 (95% CI: 2.9-41.4), P = 0.00008. The mean maximal MRI measured outgrowth was 4.9 mm (95% CI: 3.7-6.1 mm) in patients without distant metastases, while the mean maximal outgrowth was 11.5 mm (95% CI: 7.8-15.2 mm) in the patients with metastases, P = 0.000006.

CONCLUSION: There is good agreement between TRUS and MRI in the pretreatment sub-classification of ≥ T3 tumors. Distant metastases are more frequent in the advanced group.

Colonoscopic high frequency mini-probe ultrasound is more accurate than conventional computed tomography in the local staging of colonic cancer

AIM

Colonoscopic high frequency mini-probe ultrasound was compared prospectively with CT in the local staging of colonic cancer.

METHOD

Consecutive patients undergoing surgical resection for colonic cancer were recruited. Preoperative 64-slice CT staging with multiplanar reconstruction was compared with colonoscopic high frequency mini-probe ultrasound using 12 MHz and 20 MHz probes. The three methods of staging (CT, 12 MHz ultrasound and 20 MHz ultrasound) were compared with the histological stage of the resected specimen. This was done using weighted kappa coefficients where weights of 0.7-0.8 were given to penalize disagreements of one level in either direction and weights of zero were given to penalize disagreements of more than one level in any direction.

RESULTS

In total, 38 patients with colonic cancer were included. They were located in the sigmoid (n = 20), descending (n = 5), ascending (n = 2) and transverse colon (n = 1) and in the caecum (n = 7) and splenic (n = 2) and hepatic (n = 1) flexure. Histopathological assessment revealed seven pT1, four pT2, 25 pT3 and two pT4 cancers. In relation to the pathology the weighted kappa coefficients were 0.36 (SE = 0.14), 0.81 (SE = 0.16) and 0.81 (SE = 0.17) for CT, ultrasound 12 MHz and ultrasound 20 MHz. Histopathologically 15 (39.5%) patients were lymph node positive. The sensitivity, specificity and kappa coefficient for detection of nodal disease for CT were 80%, 47.8% and 0.25 (SE = 0.14) compared with 80%, 82.5% and 0.62 for 12 MHz ultrasound (SD = 0.14) and 23%, 90.5% and 0.15 (SD = 0.13) for 20 MHz ultrasound.

CONCLUSION

Colonoscopic ultrasound is significantly more accurate than CT for T staging of colonic cancers. With respect to nodal status, 12 MHz ultrasound offers superior accuracy to CT or 20 MHz ultrasound.

Application of endoscopic sonography in preoperative staging of rectal cancer: six-year experience

OBJECTIVES

The aim of this study was to evaluate our experience with the application of endoscopic sonography in preoperative staging of rectal cancer.

METHODS

Between April 2004 and May 2010, 192 patients with rectal cancer first underwent endoscopic sonography and then underwent surgery at our hospital. None of the patients in this study received neoadjuvant therapy. The endoscopic sonographic staging results were compared with those of postoperative pathologic staging.

RESULTS

The accuracy of overall T staging was 86.5%, and for T1, T2, T3, and T4, the accuracy rates were 86.7%, 94.0%, 86.2%, and 65.5%, respectively. The accuracy of T staging for ulcerated lesions was significantly lower than that for nonulcerated lesions (P = .013). The accuracy of T staging between nontraversable stenotic lesions and traversable lesions was also significantly different (P = .002). The accuracy of N staging was 77.8%, and the specificity and sensitivity were 85.6% and 74.2%, respectively.

CONCLUSIONS

Endoscopic sonography is safe and effective for preoperative staging of rectal cancer and should be a routine examination before surgery. As for ulcerated and nontraversable stenotic lesions, however, the results of endoscopic sonographic staging could be doubtful. Moreover, the accuracy of endoscopic sonographic N staging still needs modification by further research.

Multivariate random-effects approach: for meta-analysis of cancer staging studies

RATIONALE AND OBJECTIVES

Meta-analyses of diagnostic accuracy studies produce summary estimates of sensitivity and specificity. Cancer staging relies on staging systems and meta-analysis is often performed after dichotomization of the staging results. For each dichotomization, summary estimates of sensitivity and specificity can be calculated by repeated bivariate random-effects analyses. In this process, staging information is lost and under- and overstaging can not be adequately expressed.

MATERIALS AND METHODS

We propose a new multivariate random-effects approach, which is an extension of the bivariate random-effects approach. To illustrate the principles and outcomes of both approaches, we used data from a meta-analysisevaluating endoluminal ultrasonography in staging of rectal cancer. In the multivariate approach, results on correct staging and under- and overstaging were calculated. In addition, the results from this analysis were used to calculate sensitivity and specificity estimates for each dichotomization and these estimates were compared with the results of the repeated bivariate analyses.

RESULTS

By the multivariate analysis, results on correct staging and under- and overstaging were obtained. The sensitivity and specificity estimates for the dichotomizations, calculated from the results of this multivariate approach, were also comparable with the sensitivity and specificity estimates obtained by the repeated bivariate analyses.

CONCLUSIONS

The multivariate random-effects approach can be a useful meta-analytic method for summarizing cancer staging data presented in diagnostic accuracy studies.

Imaging for Predicting the Risk Factors—the Circumferential Resection Margin and Nodal Disease—of Local Recurrence in Rectal Cancer: A Meta-Analysis

The aim of the present study was to conduct a meta-analysis of English literature on the accuracy of preoperative imaging in predicting the two most important risk factors for local recurrence in rectal cancer, the circumferential resection margin (CRM) and the nodal status (N-status). Articles published between 1985 and August 2004 that report on the diagnostic accuracy of endoluminal ultrasound (EUS), computed tomography (CT), or magnetic resonance imaging (MRI) in the evaluation of lymph node involvement were included. A similar search was done for the assessment of the circumferential resection margin in rectal cancer in the period from January 1985 till January 2005. The inclusion criteria were as follows: (1) more than 20 patients with histologically proven rectal cancer were included, (2) histology was used as the gold standard, and (3) results were given in a 2 x 2 contingency table or this table could otherwise be extracted from the article by two independent readers. Based on the results summary receiver operating characteristic (ROC) curves were constructed. Only 7 articles matching inclusion criteria were found concerning the CRM. The meta-analysis shows that MRI is rather accurate in diagnosing a close or involved CRM. For nodal status 84 articles could be included. The diagnostic odds ratio of EUS is estimated at 8.83. For MRI and CT, the diagnostic odds ratio are 6.53 and 5.86, respectively. The results show that EUS is slightly, but not significantly, better than MRI or CT for identification of nodal disease. There is no significant difference between the different modalities with respect to staging nodal status. At present, MRI is the only modality that predicts the circumferential resection margin with good accuracy, making it a good tool to identify high and low risk patients. Predicting the N-status remains a problem for the radiologist for every modality, although considering the new developments in MR imaging, this may change in the near future.

Rectal cancer: local staging and assessment of lymph node involvement with endoluminal US, CT, and MR imaging--a meta-analysis

PURPOSE

To perform a meta-analysis to compare endoluminal ultrasonography (US), computed tomography (CT), and magnetic resonance (MR) imaging in rectal cancer staging.

MATERIALS AND METHODS

Relevant articles published between 1985 and 2002 were included if more than 20 patients were studied, histopathologic findings were the reference standard, and data were presented for 2 x 2 tables; articles were excluded if data were reported elsewhere in more detail. Two reviewers independently extracted data on study characteristics and results. Bivariate random-effects approach was used to obtain summary estimates of sensitivity and specificity for invasion of muscularis propria, perirectal tissue, and adjacent organs and for lymph node involvement. Summary receiver operating characteristic (ROC) curves were fitted for perirectal tissue invasion and lymph node involvement.

RESULTS

Ninety articles fulfilled all inclusion criteria. For muscularis propria invasion, US and MR imaging had similar sensitivities; specificity of US (86% [95% confidence interval [CI]: 80, 90]) was significantly higher than that of MR imaging (69% [95% CI: 52, 82]) (P =.02). For perirectal tissue invasion, sensitivity of US (90% [95% CI: 88, 92]) was significantly higher than that of CT (79% [95% CI: 74, 84]) (P <.001) and MR imaging (82% [95% CI: 74, 87]) (P =.003); specificities were comparable. For adjacent organ invasion and lymph node involvement, estimates for US, CT, and MR imaging were comparable. Summary ROC curve for US of perirectal tissue invasion showed better diagnostic accuracy than that of CT and MR imaging. Summary ROC curves for lymph node involvement showed no differences in accuracy.

CONCLUSION

For local invasion, endoluminal US was most accurate and can be helpful in screening patients for available therapeutic strategies.

Role of endoscopy in staging colorectal cancer

The treatment of colorectal cancer depends in large measure on the depth of tumor invasion and the extent of lymph node involvement. Endoscopic ultrasonography (EUS) has added a new dimension to the evaluation of tumor invasion and lymph node involvement in gastrointestinal cancer. The overall EUS accuracy for colorectal cancer T-staging is 78%, specificity is 73%, and sensitivity is 94%. In determining the nodal involvement by tumor, EUS has an accuracy of 75%, specificity of 73%, and sensitivity of 74%. Comparison with computerized tomography (CT), magnetic resonance imaging (MRI), and MRI with endorectal coil (MRIEC) shows that EUS is an effective single modality for assessing tumor penetration of the rectal wall. It does not, however, allow the assessment of distant metastatic disease. For assessing lymph node involvement, MRIEC offers the most comprehensive information.