Accuracy of CT prediction of poor prognostic features in colonic cancer

Diagnostic accuracy of computed tomography for colon cancer staging: a systematic review

BACKGROUND

Computed Tomography (CT) is a frequently used staging modality for colon cancer patients in clinical practice. Our aim was to systemically review the available literature on diagnostic accuracy of CT for TNM staging of colon cancer.

METHODS

A systematic review of literature was performed. PubMed was searched using MeSH terms with the following search terms: "Tomography, X-Ray Computed" or "Tomography, Spiral Computed" and Colonic Neoplasms. Studies on rectal cancer and studies without separate analyses for the colon were excluded. We identified 779 publications, of which 11 were included for review. Overall and sample-size-weight sensitivity, specificity, accuracy, true-positive, true-negative, false-positive, false-negative, positive and negative predictive values were calculated for T, N and M stages.

RESULTS

In the 11 studies, a total of 753 patients with 759 colon cancers underwent CT for staging. Sample-size-weighted sensitivity, specificity and accuracy for T-staging was 77%, 3% and 67%, respectively; for N-staging 76%, 55% and 69%, respectively; and for M-staging 85%, 98% and 95%, respectively. Additional clinical findings were reported in 59/372 (16%) patients, with 12 having a malignant and 47 a benign origin.

CONCLUSIONS

While accuracy of CT for TN-staging of colon cancer is only reasonable, the real value of CT is its high accuracy to detect distant metastases.

The value of true axial imaging for CT staging of colonic cancer

OBJECTIVE

To assess the effect of true axial computed tomography on the accuracy of staging of colonic cancers.

METHOD

Fifty consecutive datasets were independently assessed by three radiologists, experienced in colorectal cancer staging. The first read was of standard axial images only. The second read was 6 weeks later and true axial images, through the tumour and perpendicular to its long axis, were included.

RESULTS

The overall accuracy for tumour staging was 56% for reader 1, 48% for reader 2 and 64% for reader 3 for standard axial CT. This improved to 72% (p = 0.012), 66% (p = 0.012) and 80% (p = 0.021) when the true axial images were added. For nodal staging, overall accuracy improved from 56% to 70% (p = 0.065) for reader 1, 58% to 76% (p = 0.012) for reader 2 and 60% to 76% (p = 0.021) for reader 3 between reads.

CONCLUSION

The accuracy of CT staging of colonic tumours is significantly improved by reviewing images reconstructed in a plane perpendicular to the long axis of the tumour. The accuracy achieved by this analysis is similar to that of CT colonography but avoids the extra complexity, additional cost and increased complications.

Diagnostic precision of CT in local staging of colon cancers: a meta-analysis

AIM

To determine the accuracy of computed tomography (CT) in detecting disease with invasion beyond the muscularis propria (MP) and malignant lymph nodes.

MATERIALS AND METHODS

A literature search of Ovid, Embase, the Cochrane database, and Medline using Pubmed, Google Scholar and Vivisimo search engines was performed to identify studies reporting on the accuracy of CT to predict the staging of colonic tumours. Publication bias was demonstrated by Funnel plots. The sensitivity, specificity, and diagnostic odds ratio (DOR) were calculated using a bivariate random effects model and hierarchical summary operating curves (HSROC) were generated.

RESULTS

Nineteen studies fulfilled all the necessary inclusion criteria. The pooled sensitivity, specificity, DOR for detection of tumour invasion were 86% (95% CI: 78-92%); 78% (95% CI: 71-84%); 22.4 (95% CI: 11.9-42.4). Similarly, the values for nodal detection were 70% (95% CI: 63-73%); 78% (95% CI: 73-82%); 8.1(95% CI: 4.7-14.1). In the subgroup analysis, the best results were obtained in studies utilizing multidetector CT (MDCT).

CONCLUSION

Preoperative staging CT accurately distinguishes between tumours confined to the bowel wall and those invading beyond the MP; however, it is significantly poorer at identifying nodal status. MDCT provides the best results.

[The significance of elastic staining in detecting vascular invasion in colorectal carcinoma]

Venous invasion (VI) is one of the most important prognostic factors in colorectal carcinomas (CRC). The interobserver variation of this feature varies between 10% and 89.5%, mainly due to the specimen processing and staining. VI was assessed using haematoxylin and eosin (H+E) alone in 611 cases and with elastic stain (orcein-haematoxylin) in 243 CRCs. The stage, the pattern of invasion and the presence of intramural and extramural VI were determined. VI was identified in 27.45% of the H+E stained sections and in 67.1% using elastic stain counterstained with haematoxylin. The incidence of VI proved stage dependent as it has been noted in 13% of Dukes A, 36% of Dukes B, 80% of Dukes C and in 83% of CRCs with distant metastasis. The pattern of invasion is strongly connected to the VI, accordingly, VI could be identified in 82% of CRCs with invasive and only in 44% with expansive margin. The use of elastic stain did not help in differentiation of extramural tumour deposits due to the damage of elastic membranes in the vascular walls and the presence of elastic fibres in the lymph node capsule. As a conclusion, the routine use of elastic stains in our practice doubled the identification of VI. The frequency of VI depends on the stage and pattern of invasion in CRCs. As it is more likely to occur in the advanced CRCs, the use of elastic stain is even more suggested in Dukes B carcinomas with invasive margin.

Evaluation of a rabbit rectal VX2 carcinoma model using computed tomography and magnetic resonance imaging

AIM: To establish a rabbit rectal VX2 carcinoma model for the study of rectal carcinoma.

METHODS: A suspension of VX2 cells was injected into the rectum wall under the guidance of X-ray fluoroscopy. Computed tomography (CT) and magnetic resonance imaging (MRI) were used to observe tumor growth and metastasis at different phases. Pathological changes and spontaneous survival time of the rabbits were recorded.

RESULTS: Two weeks after VX2 cell implantation, the tumor diameter ranged 4.1-5.8 mm and the success implantation rate was 81.8%. CT scanning showed low-density foci of the tumor in the rectum wall, while enhanced CT scanning demonstrated asymmetrical intensification in tumor foci. MRI scanning showed a low signal of the tumor on T₁-weighted imaging and a high signal of the tumor on T₂-weighted imaging. Both types of signals were intensified with enhanced MRI. Metastases to the liver and lung could be observed 6 wk after VX2 cell implantation, and a large area of necrosis appeared in the primary tumor. The spontaneous survival time of rabbits with cachexia and multiple organ failure was about 7 wk after VX2 cell implantation.

CONCLUSION: The rabbit rectal VX2 carcinoma model we established has a high stability, and can be used in the study of rectal carcinoma.

CT staging of colon cancer

Computer tomography (CT) has been the principal investigation in the staging of colon cancers. The information obtained with routine CT has been limited to identifying the site of the tumour, size of the tumour, infiltration into surrounding structures and metastatic spread. The Foxtrot trial National Cancer Research Institute (NCRI) has been specifically designed to evaluate the efficacy of neoadjuvant treatment in colon cancers by using preoperative chemotherapy with or without an anti-Epidermal Growth Factor Receptor (EGFR) monoclonal antibody to improve outcome in high-risk operable colon cancer. Patients are selected based on their staging CT examination. The criteria for poor prognosis are T4 and T3 tumours with more than 5mm extramural depth. Thus the success of the trial would depend upon the confidence of the radiologist to identify the patients that would receive the neoadjuvant treatment. The aim of this review is to explain the process of identifying high-risk features seen on the staging CT images. This will help to identify a cohort of patients that could truly benefit from neoadjuvant strategies.