Accuracy of CT colonography in the preoperative staging of colon cancer: a prospective study of 217 patients

Computed Tomography Colonography: 2025 Update

Colorectal cancer (CRC) is the second leading cause of cancer-related deaths in the United States. Most cases arise from polyps, which can be detected and removed before becoming cancerous. Computed tomography colonography (CTC), also known as virtual colonoscopy, was first introduced in 1994 as a minimally invasive method for CRC screening and diagnosis. This 2025 update on CTC will focus on (1) techniques and dose reduction strategies, (2) image display methods, (3) reporting and classification systems, (4) tumor staging capabilities, (5) integration of advanced imaging techniques, and (6) cost-effectiveness and reimbursement.

Prognostic significance of the retroperitoneal surgical resection margin on computed tomography colonography in retroperitonealized colon cancer

BACKGROUND

A positive pathologic retroperitoneal surgical resection margin in the retroperitonealized colon is reported to predict distant metastases. However, no studies have investigated retroperitoneal surgical resection margin positivity on computed tomography colonography and its prognostic significance.

METHODS

Patients who underwent primary resection for ascending or descending colon cancer at our institution between 2013 and 2018 were retrospectively evaluated (n = 206). Retroperitoneal surgical resection margin on computed tomography colonography was defined on the basis of the relationship between the advanced tumor area and the retroperitoneum. The relationship between retroperitoneal surgical resection margin on computed tomography colonography and relapse-free survival was analyzed by dividing the patients into positive and negative retroperitoneal surgical resection margin on computed tomography colonography groups.

RESULTS

Two doctors independently evaluated the images. The interobserver agreement rate was 93.7% with a kappa coefficient of 0.78 (95% confidence interval, 0.66-0.90). Retroperitoneal surgical resection margin on computed tomography colonography positivity was observed in 32 of the 206 patients (15.5%). Univariate analysis showed that a positive retroperitoneal surgical resection margin on computed tomography colonography was a poor prognostic factor for relapse-free survival (hazard ratio, 7.07; 95% confidence interval, 2.77-18.0, P < .001). Multivariate analysis with carcinoembryonic antigen, clinical T and N stage as covariates (all P < .10 in univariate analysis) identified only retroperitoneal surgical resection margin on computed tomography colonography positive as a significant independent poor prognostic factor for relapse-free survival (hazard ratio, 3.99; 95% confidence interval, 1.30-12.3, P = .02).

CONCLUSION

In conclusion, this study revealed that retroperitoneal surgical resection margin on computed tomography colonography positivity is a poor prognostic factor. In cases in which retroperitoneal surgical resection margin on computed tomography colonography is positive, it is recommended not only to secure a wider margin, such as by resecting the Gerota fascia, but also to consider retroperitoneal surgical resection margin on computed tomography colonography positivity as a potential indication for preoperative chemotherapy.

High-performance CT features supporting accurate pre-operative tumor staging in colon cancer

Background and aims

Accurate pre-treatment tumor staging is essential for treatment decision-making. Multi-slice spiral computed tomography (CT) is currently the standard method for pre-operative clinical tumor staging, but accurately applying the CT findings in tumor staging remains a challenge due to the poor pathological understanding of the CT signs. We aimed to pathologically interpret the key CT findings in order to identify reliable markers for pre-treatment staging of colon cancer.

Patients and methods

The following CT features from 136 colon adenocarcinomas were analyzed: colon wall pliability, outline contour, pericolic fat attenuations and vascularity, tumor fusion with adjacent organs, ascites, tumor size, and relevance between tumor and retroperitoneal fascia. These CT features were corroborated with histopathological findings. The diagnostic performance of these was further analyzed.

Results

Based on the postoperative pathological tumor staging (pT), 136 colon adenocarcinomas were classified into four stages: pT1 (n = 5), pT2 (n = 7), pT3 (n = 96), and pT4 (n = 28). Key findings include the following: (1) soft colon wall is a characteristic of the pT1 tumors, whereas stiff colon wall is a characteristic of the pT2~pT4 tumors; pathologically, stiff colon wall reflects the infiltration of tumor cells with desmoplastic reaction (DR) in muscularis propria; (2) small protuberances may help exclude the pT2 tumors. Histopathologically, small protuberances in pT2 cancer represent the pure DR on the surface of lamina propria, whereas the small protuberances in pT3~pT4 cancers represent the sub-serosal or extra-serosal cancer cell foci enwrapped by DR; (3) the presence of large protuberances, extensive reticulonodular fat stranding, and fusion with surrounding organs and ascites are diagnostic of pT4 tumors; and (4) the presence of extra-fascial nodules/streaks on CT scan could accurately diagnose the ascending/descending colon cancer of pT4 stage. Histologically, the presence of the above five CT features (large protuberances, extensive reticulonodular fat stranding, fusion with surrounding organs, ascites, and extra-fascial nodules/streaks) reflect the farther and deeper infiltration of tumor cells in serosa or retroperitoneal fascia involvement.

Conclusion

Our studies have identified multiple CT features that are practically useful in identifying and differentiating different stages of colon cancer prior to surgical procedures. These high-performance markers will provide valuable insights to the clinicians in making appropriate decisions in the management of patients with colon cancer.

Prospective observational non-randomized trial protocol for surgical planner 3D image processing & reconstruction for locally advanced colon cancer

INTRODUCTION

Colon cancer presents significant surgical challenges that necessitate the development of precise strategies. Standardization with complete mesocolic excision (CME) is common, but some cases require extended resections. This study investigates the use of 3D Image Processing and Reconstruction (3D-IPR) to improve diagnostic accuracy in locally advanced colon cancer (LACC) with suspected infiltration and achieve R0 surgery.

METHODS

Single-center, prospective, observational, comparative, non-randomized study. •Participants: Patients aged > 18 years undergoing LACC surgery, as indicated by CT scans, confirmed via colonoscopy. Exclusion criteria include neoadjuvant therapy, suspected carcinomatosis on CT, and unresectable tumors. •Interventions: 3D-IPR models are used for surgical planning, providing detailed tumor and surrounding structure metrics. Surgical procedures are guided by CT scans and intraoperative findings, categorized by surgical margins as R0, R1, or R2. •Objective: The primary goal is to evaluate 3D-IPR's utility in achieving R0 resection in LACC with suspected infiltration. Secondary objectives include assessing preoperative surgical strategy, comparing CT reports, detecting adenopathy, and identifying vascularization and anatomical variants. • Outcome: The main outcome is the diagnostic accuracy of 3D-IPR in determining tumor infiltration of neighboring structures compared to conventional CT scans, using definitive pathological reports as the gold standard.

RESULTS

•Recruitment and Number Analyzed: The study aims to recruit about 20 patients annually over two years, focusing on preoperative 3D-IPR analysis and subsequent surgical procedures. •Outcome Parameters: These include loco-regional and distant recurrence rates, peritoneal carcinomatosis, disease-free and overall survival, and mortality due to oncologic progression. •Harms: No additional risks from CT scans, as they are mandatory for staging colon tumors. 3D-IPR is derived from these CT scans.

DISCUSSION

If successful, this study could provide an objective tool for precise tumor extension delimitation, aiding decision-making for radiologists, surgeons, and multidisciplinary teams. Enhanced staging through 3D-IPR may influence therapeutic strategies, reduce postsurgical complications, and improve the quality of life of patients with LACC.

TRIAL REGISTRATION

Trial is registered at ISRCTN registry as ISRCTN81005215. Protocol version I (Date 29/06/2023).

Canadian Association of Radiologists Practice Guidelines for Computed Tomography Colonography

Colon cancer is the third most common malignancy in Canada. Computed tomography colonography (CTC) provides a creditable and validated option for colon screening and assessment of known pathology in patients for whom conventional colonoscopy is contraindicated or where patients self-select to use imaging as their primary modality for initial colonic assessment. This updated guideline aims to provide a toolkit for both experienced imagers (and technologists) and for those considering launching this examination in their practice. There is guidance for reporting, optimal exam preparation, tips for problem solving to attain high quality examinations in challenging scenarios as well as suggestions for ongoing maintenance of competence. We also provide insight into the role of artificial intelligence and the utility of CTC in tumour staging of colorectal cancer. The appendices provide more detailed guidance into bowel preparation and reporting templates as well as useful information on polyp stratification and management strategies. Reading this guideline should equip the reader with the knowledge base to perform colonography but also provide an unbiased overview of its role in colon screening compared with other screening options.

Effect of visceral fat area on the accuracy of preoperative CT-N staging of colorectal cancer

OBJECTIVE

To investigate the effect of visceral fat area (VFA) on the accuracy of preoperative CT-N staging of colorectal cancer.

METHODS

We retrospectively reviewed the clinical and imaging data of 385 CRC patients who underwent surgical resection for colorectal cancer between January 2018 and July 2021. Preoperative CT-N staging and imaging features were determined independently by two radiologists. Using postoperative pathology as the gold standard, patients were divided into accurately and incorrectly staged groups, and clinical and imaging characteristics were compared between the two groups. VFA and subcutaneous fat area (SFA) at the L3 vertebral level, sex, age, BMI, tumor location, size, and tumor circumference ratio (TCR) were included. Logistic regression analysis was used to evaluate the independent factors influencing the accuracy of preoperative N staging of colorectal cancer.

RESULTS

Of the 385 patients enrolled, 259 (67.27%) were in the preoperative N-stage accurate staging group, and 126 (32.73%) were in the incorrectly staged group. Univariate analysis showed that there were significant differences in BMI, tumor location, VFA, SFA, size and TCR between the two groups (P<0.05). Logistic regression analysis showed that VFA (95% CI: 1.277, 3.813; P=0.005) and TCR (95% CI: 1.649, 17.545; P=0.005) were independent factors affecting the accuracy of N staging. The optimal cutoff points for VFA and TCR in predicting incorrect staging were 110 cm2 and 0.675, respectively.

CONCLUSIONS

Colorectal cancer patients with lower VFA and higher TCR and preoperative CT-N staging had an increased risk for diagnostic errors.

Diagnostic Accuracy of Abdominal CT for Locally Advanced Colon Tumors: Can We Really Entrust Certain Decisions to the Reliability of CT?

Many different options of neoadjuvant treatments for advanced colon cancer are emerging. An accurate preoperative staging is crucial to select the most appropriate treatment option. A retrospective study was carried out on a national series of operated patients with T4 tumors. Considering the anatomo-pathological analysis of the surgical specimen as the gold standard, a diagnostic accuracy study was carried out on the variables T and N staging and the presence of peritoneal metastases (M1c). The parameters calculated were sensitivity, specificity, positive and negative predictive values, and positive and negative likelihood ratios, as well as the overall accuracy. A total of 50 centers participated in the study in which 1950 patients were analyzed. The sensitivity of CT for correct staging of T4 colon tumors was 57%. Regarding N staging, the overall accuracy was 63%, with a sensitivity of 64% and a specificity of 62%; however, the positive and negative likelihood ratios were 1.7 and 0.58, respectively. For the diagnosis of peritoneal metastases, the accuracy was 94.8%, with a sensitivity of 40% and specificity of 98%; in the case of peritoneal metastases, the positive and negative likelihood ratios were 24.4 and 0.61, respectively. The diagnostic accuracy of CT in the setting of advanced colon cancer still has some shortcomings for accurate diagnosis of stage T4, correct classification of lymph nodes, and preoperative detection of peritoneal metastases.

Radiologic T staging of colon cancer: renewed interest for clinical practice

Radiologic imaging, especially MRI, has long been the mainstay for rectal cancer staging and patient selection for neoadjuvant therapy prior to surgical resection. In contrast, colonoscopy and CT have been the standard for colon cancer diagnosis and metastasis staging with T and N staging often performed at the time of surgical resection. With recent clinical trials exploring the expansion of the use of neoadjuvant therapy beyond the anorectum to the remainder of the colon, the current and future state of colon cancer treatment is evolving with a renewed interest in evaluating the role radiology may play in the primary T staging of colon cancer. The performance of CT, CT colonography, MRI, and FDG PET-CT for colon cancer staging will be reviewed. N staging will also be briefly discussed. It is expected that accurate radiologic T staging will significantly impact future clinical decisions regarding the neoadjuvant versus surgical management of colon cancer.

Imaging of colon and rectal cancer

Colon and rectal cancer imaging has traditionally been performed to assess for distant disease (typically lung and liver metastases) and to assess the resectability of the primary tumor. With technological and scientific advances in imaging and the evolution of treatment options, the role of imaging has expanded. Radiologists are now expected to provide a precise description of primary tumor invasion extent, including adjacent organ invasion, involvement of the surgical resection plane, extramural vascular invasion, lymphadenopathy, and response to neoadjuvant treatment, and to monitor for recurrence after clinical complete response.

Using structured templates or free text style in reporting CT staging on colon cancer: a national survey

BACKGROUND

Computed tomography (CT) is a widely used method for the staging of colon cancer. Accurate reports could lead to a better preoperative evaluation and planning of the treatment of colon cancer.

PURPOSE

To evaluate the use of CT free-text reports and structured report templates when it comes to staging CT imaging of colon cancer.

MATERIAL AND METHODS

A multiple choice questionnaire survey was conducted over four weeks. Online questionnaire software was used, and a link was shared to medical doctors with help from the Danish Colorectal Cancer Group (DCCG) and from a social media radiologist group.

RESULTS

Clinicians preferred the template style (95%), whereas the level of support was lower among the radiologists (76%). All female responders preferred the template style, in contrast to only 84% of the male responders. Furthermore, the survey showed a slightly deficient level of the national CT reporting quality; only 7/13 questions and sub-questions, concerning CT report quality, achieved an approval rate >85%. The colorectal cancer multidisciplinary team consultants who always or usually work with template style reporting of CT scans of colon cancer tend to be more satisfied with the quality and content of the reports, compared to those who rarely use or read template reports.

CONCLUSION

The following indicators were insufficiently reported: tumor invasion growth; number of hepatic metastases; segment location of hepatic metastasis; and retroperitoneal lymph node involvement. In the template reports group, nearly all participants found relevant information easily accessible.

Colon cancer CT staging according to mismatch repair status: Comparison and suggestion of imaging features for high-risk colon cancer

BACKGROUND

Neoadjuvant treatment with either chemotherapy or immunotherapy is gaining momentum in colon cancers (CC). To reduce over-treatment, increasing staging accuracy using computed tomography (CT) is of high importance.

PURPOSE

To assess and compare CT imaging features of CC between mismatch repair-proficient (pMMR) and MMR-deficient (dMMR) tumours and identify CT features that can distinguish high-risk (pT3-4, N+) CC according to MMR status.

METHODS

Primary staging CTs of 266 patients who underwent primary surgical resection of a colon tumour were retrospectively and independently evaluated by two radiologists. Logistic regression analysis was performed to identify significant associations between imaging features and positive lymph node status. Receiver operating characteristic (ROC) curves of significantly associated features were assessed and validated in an external cohort of 104 patients.

RESULTS

Among pT3 tumours only, dMMR CC were significantly larger than pMMR CC in both length and thickness (length 59.39 ± 26.28 mm versus 48.70 ± 23.72, respectively, p = 0.031; thickness 20.54 mm ± 11.17 versus 16.34 ± 8.73, respectively, p = 0.027). For pMMR tumours, nodal internal heterogeneity on CT was significantly associated with a positive lymph node status (odds ratio (OR) = 2.66, p = 0.027), while for dMMR tumours, the largest short diameter of the nodes was associated with lymph node status (OR = 2.01, p = 0.049). The best cut-off value of the largest short diameter of involved nodes was 10.4 mm for dMMR and 7.95 mm for pMMR. In the external validation cohort, AUCs for predicting involved nodes based on the largest short diameter was 0.764 for dMMR tumours using 10 mm size cut-off and 0.624 for pMMR tumours using 7 mm cut-off.

CONCLUSION

These data show that CT imaging features of primary CC differ between dMMR and pMMR tumours, suggesting that the assessment of CT-based CC staging should take MMR status into consideration, especially for lymph node status, and thus may help in selecting patients for neoadjuvant treatment.

Diagnostic accuracy of ≥ 16-slice spiral computed tomography for local staging of colon cancer: A systematic review and meta-analysis

BACKGROUND

Colorectal cancer is one of the most common cancers worldwide with high mortality and is classified as a single entity, although colon cancer and rectal cancer have largely different diagnoses, treatments, surgical methods, and recurrence rates. ≥ 16-slice spiral computed tomography (SCT) is mostly applied to detect the local stage of colon cancer; however, its diagnostic accuracy and whether it is conducive to distinguishing between high-risk and low-risk colon cancer are unclear.

AIM

To systematically review the diagnostic accuracy of ≥ 16-slice SCT for local staging of colon cancer.

METHODS

Based on the PubMed, EMBASE, Cochrane Library, and Web of Science databases, computers were used to search the literature from the establishment of the database to April 2021, and the results of the diagnostic tests on ≥ 16-slice SCT for local staging of colon cancer were collected according to the inclusion criteria. The data were then extracted and assessed on the basis of the Quality Assessment Checklist of the Institute of Economics of Canada, Reference Citation Analysis (https://www.referencecitationanalysis.com/). Afterward, a meta-analysis was performed using the statistical software Meta-disc 14.0 and Stata 15.0.

RESULTS

Eleven studies that provided data on 1613 subjects with computed tomography diagnostic tests were included in this study. Meta-analysis revealed that the pooled sensitivity, pooled specificity, pooled negative likelihood ratio (LR), pooled diagnostic odds ratio, and area under the fitted receiver operating characteristic (ROC) curve of ≥ 16-slice SCT for colon cancer T staging were 0.67 (95%CI: 0.65-0.70), 0.81 (95%CI: 0.80-0.83), 4.13 (95%CI: 2.66-6.41), 0.39 (95%CI: 0.31-0.49), 10.81 (95%CI: 7.33-15.94), and 0.829, respectively, while the specificity, negative LR, diagnostic odds ratio, and area under the fitted ROC curve of ≥ 16-slice SCT for N staging of colon cancer were 0.54 (95%CI: 0.49-0.59), 0.74 (95%CI: 0.70-0.77), 1.92 (95%CI: 1.36-2.70), 0.67 (95%CI: 0.51-0.87), 3.74 (95%CI: 1.76-7.94), and 0.829 respectively. The sensitivity and specificity of ≥ 16-slice SCT for colon cancer T staging were acceptable, while the sensitivity for colon cancer N staging was relatively low, though its specificity was acceptable.

CONCLUSION

≥ 16-slice SCT for local staging of colon cancer has good diagnostic value; however, the accuracy needs to be confirmed by further clinical practice.

Computed Tomography Colonography Angiography (CTC-A) prior to colectomy for cancer: A new tool for surgeons

The pre-operative work-up for non-metastatic colon cancer includes colonoscopy and thoraco-abdomino-pelvic computed tomography (CT) with intravenous (IV) contrast. Colonoscopic determination of the anatomical location of the tumor may be erroneous, particularly with a long redundant colon (dolichocolon), and the search for synchronous colon neoplasms is limited when the endoscope cannot traverse the tumor-bearing segment. While computed tomography colonography angiography (CTC-A) makes it possible to assess distant tumor metastasis, it remains limited for the assessment of loco-regional extension. CTC-A requires specific colonic preparation, controlled colonic insufflation with CO₂, and an injection of IV contrast. CTC-A provides a 3-D view of the overall morphology of the colon and precisely localizes the site of the colonic tumor. Merging the images of the colon with those of mesenteric and colonic vessels provides a representation of anatomical vascular variations. This information could help the surgeon to better plan the colectomy. The use of two-dimensional images of CTC-A with sections perpendicular to the major axis of the tumor-bearing colonic segment can provide precise information on the degree of parietal extension and be useful in evaluating the value of neo-adjuvant chemotherapy.

Preoperative T staging of advanced colorectal cancer by computed tomography colonography

PURPOSE

Accurate preoperative T staging is important when determining the treatment strategy for advanced colorectal cancer. We have previously reported the usefulness of preoperative T staging based on the spatial relationship of tumors and "bordering vessels" by computed tomography colonography (CTC) with multiplanar reconstruction (MPR). The aims of this study were to evaluate the external validity of this method and to determine whether there is a difference in the accuracy of T staging between the mesenteric and antimesenteric sides.

METHODS

The study subjects were 110 patients with colorectal cancer who underwent preoperative CTC and surgical resection from June 2016 to March 2018. Preoperative T stage was determined by CTC based on the relationship between the tumor and the bordering vessels and compared with the pathological T stage. The influence of tumor location, namely, whether the tumor was on the antimesenteric or mesenteric side, on preoperative T staging was assessed in 78 patients with colorectal cancer.

RESULTS

Sensitivity, specificity, accuracy, positive, and negative predictive values were respectively, 65%, 91%, 83%, 76%, and 85% for T2 (n = 34); 76%, 82%, 81%, 50%, and 94% for T3 (n = 23); and 77%, 93%, 87%, 86%, and 88% for T4a disease (n = 39). Overall right answer rate was 83.3% (15/18) for the mesenteric side and 65% (39/60) for the antimesenteric side (n = 0.14).

CONCLUSION

Diagnostic criteria based on the bordering vessels seen on CTC images with MPR are useful for T staging of colorectal cancer. However, the accuracy differs between the antimesenteric and mesenteric sides.

Surgical treatment strategy for locally advanced colorectal cancer with abdominal wall invasion

Background

The incidence of abdominal wall metastasis from colorectal cancer (CRC) is very low, but it has a poor prognosis. Despite the advances in radiotherapy, chemotherapy, and targeted therapy, patient prognosis has not improved significantly. Through surgical treatment, some patients with locally advanced CRC with abdominal wall invasion can achieve tumor-free survival or an improved quality of life.

Methods

The clinical data of 15 patients in our department from January 2015 to January 2020 were retrospectively analyzed. All patients underwent preoperative three-dimensional reconstruction of the tumor and abdominal wall after discussion with a multidisciplinary team (MDT). Patient information, including tumor size, defect size, operation time, intraoperative bleeding, hospital stay, and other factors, was collected.

Results

All 15 patients underwent resection followed by reconstruction for locally advanced CRC with abdominal wall invasion. The average tumor area and abdominal wall defects were 98.13±71.70 and 270.07±101.95 cm², respectively; and accurate abdominal wall classification and zoning were obtained for all patients. The average operation time was 431.7±189.2 min, and the average blood loss was 513.3±244.6 mL. The recurrence rates in the incisional hernia and abdominal wall were 6.0% and 13.3%, respectively. The patient survival rate was 87.7%.

Conclusions

Surgical treatment of locally advanced CRC with abdominal wall invasion is feasible, but requires accurate and comprehensive preoperative evaluation.

Pre-colectomy location and TNM staging of colon cancer by the computed tomography colonography: a diagnostic performance study

BACKGROUND

The Chinese Society of Clinical Oncology guidelines 2018 and the recent update of that (version 2020) recommends accurate examination before major treatment for decision(s) in cases of colon cancer. Also, the difficulty in the identification of the lesion during colectomy may lead to resection of a wrong segment of the colon or a more extensive resection than planned. Accurate pre-colectomy local staging of colon cancer is required to make decisions for treatment of colon cancer. The objective of the study was to evaluate the diagnostic performance of the computed tomography colonography (CTC) for pre-colectomy tumor location and tumor, node, and metastasis (TNM) staging of colon cancer.

METHODS

Data of preoperative colonoscopies, CTC, surgeries, and surgical pathology of a total of 269 patients diagnosed with colon cancer by colonoscopy and biopsy and underwent pre-colectomy location and TNM staging by CTC were collected and analyzed. The consistency between the radiological and the surgery/surgical-pathological for location and TN stages of colon tumor were estimated with the weighted kappa or kappa coefficient (κ) at 95% confidence interval (CI).

RESULTS

CTC detected 261 (93%) and colonoscopy detected 201 (72%) correct locations of tumors. Sensitivity and accuracy of CTC for detection of location of colon tumors were 100% and 92.58% (κ = 0.89; 95% Cl: 0.83-0.95). 72.48% sensitivity, 90.64% specificity, and 83.57% accuracy were reported for CTC in differentiation of tumors confined to the colon wall (T1/T2) from advanced tumors (T3/T4) (κ = 0.69, 95% Cl: 0.51-0.75). 81.01% sensitivity, 89.11% specificity, and 83.93% accuracy of CTC was reported for differentiation of tumors between low-intermediate risk and high risk (κ = 0.68, 95% Cl: 0.53-0.75). 69.31% sensitivity, 66.15% specificity, and 67.14% accuracy of CTC were reported for N staging of tumors (κ = 0.41, 95% Cl: 0.59-0.69).

CONCLUSIONS

CTC has high diagnostic parameters for pre-colectomy location and T staging of colon tumors except patients of colon cancer who received neoadjuvant chemotherapy.

LEVEL OF EVIDENCE

III.

TECHNICAL EFFICACY STAGE

2.

Computed tomography colonography and radiation risk: How low can we go?

Computed tomography colonography (CTC) has become a key examination in detecting colonic polyps and colorectal carcinoma (CRC). It is particularly useful after incomplete optical colonoscopy (OC) for patients with sedation risks and patients anxious about the risks or potential discomfort associated with OC. CTC's main advantages compared with OC are its non-invasive nature, better patient compliance, and the ability to assess the extracolonic disease. Despite these advantages, ionizing radiation remains the most significant burden of CTC. This opinion review comprehensively addresses the radiation risk of CTC, incorporating imaging technology refinements such as automatic tube current modulation, filtered back projections, lowering the tube voltage, and iterative reconstructions as tools for optimizing low and ultra-low dose protocols of CTC. Future perspectives arise from integrating artificial intelligence in computed tomography machines for the screening of CRC.

Locoregional CT staging of colon cancer: does a learning curve exist?

PURPOSE

To evaluate the learning curve for locoreginal staging of colon cancer in radiologist trainees.

METHODS

Eighty-eight cases of colon cancer CT were included in this retrospective study. Four senior radiology residents staged the CTs according to TNM classification. Two out of four radiologists received feedback after reading every 20 cases. Radiologic staging was compared with pathologic staging and the learning curve, diagnostic performance, reader confidence and reading time were evaluated and compared between the two groups (feedback vs. no feedback). Generalized estimating equations logistic regression, QICu statistic, ANOVA and t test/Mann-Whitney test were utilized.

RESULTS

Radiologists demonstrated a significant increase in their performance to distinguish between ≤ T2 and ≥ T3 and reached an inflection point at 38 cases, with a significant association with increased number of cases reviewed (P < 0.001). Sensitivity (P < 0.001), specificity (P = 0.030) and NPV (P = 0.002) demonstrated significant associations with increased experience. The overall reader's confidence was significantly higher in the group which received feedback (P < 0.001). There was no significant improvement in performance nor in reader's confidence for N staging (N0 vs. ≥ N1) for all readers. Reading time decreased with experience and showed a significant negative association with experience (P < 0.001).

CONCLUSION

Diagnostic performance of senior radiology trainees in differentiating between T2 and T3 colon cancer on CTs improved with increased experience. In contrast, evaluation of lymph node involvement did not improve with more experience. Feedback had no significant effect on improvement of diagnostic performances.

Precision image-guided colonic surgery: proof of concept for enhanced preoperative and intraoperative vascular imaging

BACKGROUND

Colorectal surgery has benefited from advances in precision medicine such as total mesorectal resection, and recently, mesocolon resection, fluorescent perfusion imaging, and fluorescent node mapping. However, these advances fail to address the variable quality of mesocolon dissection and the directed extent of vascular dissection (including high ligation) or pre-resection anastomotic perfusion mapping, thereby impacting anastomotic leaks. We propose a new paradigm of precision image-directed colorectal surgery involving 3D preoperative resection modeling and intraoperative fluoroscopic and fluorescence vascular imaging which better defines optimal dissection planes and vascular vs. anatomy-based resection lines according to our hypothesis.

METHODS

Six pigs had preoperative CT with vascular 3D reconstruction allowing for the preoperative planning of vascular-based dissection. Laparoscopic surgery was performed in a hybrid operating room (OR). Superselective arterial catheterization was performed in branches of the superior mesenteric artery (SMA) or the inferior mesenteric artery (IMA). Intraoperative boluses of 0.1 mg/kg or a continuous infusion of indocyanine green (ICG) (0.01 mg/mL) were administered to guide fluorescent-based sigmoid and ileocecal resections. Fluorescence was assessed using proprietary software at several regions of interest (ROI) in the right and left colon.

RESULTS

The approach was feasible and safe. Selective catheterization took an average of 43 min. Both bolus and continuous perfusion clearly marked pre-identified vessels (arteries/veins) and the target colon segment, facilitating precise resections based on the visible vascular anatomy. Quantitative software analysis indicated the optimal resection margin for each ROI.

CONCLUSION

Intra-arterial fluorescent mapping allows visualization of major vascular structures and segmental colonic perfusion. This may help to prevent any inadvertent injury to major vascular structures and to precisely determine perfusion-based resection planes and margins. This could enable tailoring of the amount of colon resected, ensure good anastomotic perfusion, and improve oncological outcomes.

Neoadjuvant chemotherapy in locally advanced colon cancer: a systematic review

BACKGROUND

Preoperative or neoadjuvant chemotherapy (NAC) has emerged as a novel alternative to treat locally advanced colon cancer (LACC), as in other gastrointestinal malignancies. However, evidence of its efficacy and safety has not yet been gathered in the literature. The aim of the present study was to perform an extensive review of the scientific evidence for NAC in patients with LACC.

METHODS

PubMed, EMBASE, MEDLINE and Cochrane Library were searched for a systematic review of the literature from 2010 to 2019. Six eligible studies were included, with a total of 27,937 patients, 1232 of them (4.4%) treated with NAC. There were only one randomized controlled trial, three phase II non-randomized single arm studies and two retrospective studies.

RESULTS

The baseline computed tomography scan showed that most of patients had a T3 tumor. The completion rate of the planned neoadjuvant treatment ranged from 52.5 to 93.8%. Between 97.2 and 100% of patients had the scheduled surgery. The median tumor volume reduction after NAC ranged from 62.5 to 63.7%. The anastomotic leak rate in the NAC group ranged from 0 to 7%, with no cases of postoperative mortality. There was major pathological tumor regression in 4-34.7% of cases. Between 84 and 100% of NAC patients had R0-surgery. Survival after NAC seems to be encouraging although significant improvement has only been proven in T4b tumours.

CONCLUSIONS

According to our systematic review, the NAC may be a safe and effective emerging therapeutic alternative for treating LACC. This approach, which is still being tested, increases the reliance on accurate radiological staging.

Tumor and nodal staging of colon cancer: accuracy of preoperative computed tomography at a Swedish high-volume center

Background

When deciding treatment options for patients with colon cancer, accurate staging is required. In Sweden, the main preoperative evaluation modality to determine tumor and nodal stage is computed tomography (CT).

Purpose

The aim of this study was to investigate how well the preoperative (CT-determined) clinical tumor and nodal stage (cTN) correlated with the postoperative histopathological stage (pTN). Another aim was to validate the tumor and nodal stage data in the Swedish Colorectal Cancer Registry (SCRCR).

Material and Methods

The SCRCR was used to identify patients with colon cancer, treated at a Swedish high-volume center during 2013-2016 (n = 974). Data were gathered from medical records regarding cTN and pTN stage, and predefined patient and tumor variables. The agreement between cTN and pTN was analyzed using kappa statistics.

Results

After excluding patients with either pre- or postoperative TN stage missing, 383 patients remained for further analyses. The analyses showed an agreement between cT and pT of κ: 0.27 and between cN and pN of κ: 0.21 (fair agreement). When comparing tumors with low (T1-3; N0) versus high risk (T4; N1-2), the kappa value was 0.19 (slight agreement). When comparing the SCRCR to medical records, 78% of completely staged tumors had been correctly reported.

Conclusion

The agreement between cTN and pTN was low in this study population, indicating a need for enhanced precision of the preoperative staging process. A high frequency of erroneous preoperative staging data in the SCRCR shows the need for further efforts of ensuring correct data transfers into the registry.