Rectal cancer staging: Multidetector-row computed tomography diagnostic accuracy in assessment of mesorectal fascia invasion

Diagnostic value of spiral CT energy spectrum imaging in lymph node metastasis of colorectal cancer

OBJECTIVES

To evaluate the value of preoperative CT energy spectrum imaging in detecting lymph node metastasis of colorectal cancer.

METHODS

From September 2019 to November 2021, a retrospective study was performed for the eighty-two patients with colorectal cancer through preoperative colonoscopy or surgical pathology confirmed in our hospital. Based on the lymph node metastasis status, these cases were divided into the metastasis and non-metastasis groups. GE Revolution CT scanner was used to scan the patients with energy spectrum imaging, it measured and recorded the single-energy CT values from 40 to 140 keV and various energy spectrum parameters of lymph nodes around the lesions in the arterial and venous phases, and statistically analyze the above indices.

RESULTS

In the arterial and venous phases: the single-energy CT values of 40-140 keV in the non-metastatic group were higher than those in the metastatic group (all P < 0.05); the parameter values of IC (iodine concentration), NIC (normalized iodine concentration), λ (the slope of the energy spectrum curve), and Eff-Z (effective-Z) in the non-metastatic group were higher than those in the metastatic group (all P < 0.05). Further evaluation of ROC curve showed that the higher AUC (area under curve) of the single-energy CT value of 50 keV in the arterial phase was 0.889, among the energy spectrum parameters of IC, NIC, λ, and Eff-Z, the NIC had the better diagnostic efficiency and the AUC of the NIC was 0.873, the highest AUC of the combination of NIC and λ was 0.885 when the energy spectrum parameters were combined. The higher AUC of the single-energy CT value of 60 keV in the venous phase was 0.853, among the energy spectrum parameters of IC, NIC, λ, and Eff-Z, the λ had the better diagnostic efficiency and the AUC of the λ was 0.822, the higher AUC of the combination of NIC, λ, and Eff-Z was 0.840 when the energy spectra were combined.

CONCLUSIONS

Parameters of energy spectrum CT imaging can effectively evaluate whether lymph nodes have metastases, and provide favorable imaging diagnosis basis for the range and the number of lymph nodes to be cleaned during clinical operation and can evaluate the prognosis of patients. It is worthy of clinical recommendation.

Imaging features associated with survival outcomes among colorectal cancer patients with and without KRAS mutation

Background

Mutations in Kirsten rat sarcoma proto-oncogene (KRAS) have been shown to be associated with advanced-stage colorectal cancer (CRC), negative disease outcomes, and poor response to treatment. The purpose of this study was to investigate which CT features are biomarkers for KRAS gene mutation and impact the survival outcomes of colorectal cancer patients.

Results

Of the 113 CRC patients included in the study, 46 had KRAS mutations (40.71%) and 67 had no mutations (59.29%). Regional lymph node necrosis was the only imaging feature significantly associated with KRAS mutation (P = 0.011). Higher T staging and liver, lung, and distant metastasis were prognostic factors for CRC (P = 0.014, P < 0.001, P = 0.022, P < 0.001, respectively). There were no significant differences in overall survival between patients with KRAS mutations and those without (P = 0.159). However, in patients with no KRAS mutation, those with CRC on the left side had a significantly higher rate of survival than those with CRC on the right (P = 0.005).

Conclusion

Regional lymph node necrosis may be an imaging biomarker of CRC with KRAS mutation, possibly indicating poor prognosis.

Accuracy of High Resolution Multidetector Computed Tomography in the Local Staging of Rectal Cancer

Background Magnetic resonance imaging (MRI) is the gold standard for local staging of rectal cancer. Advanced computed tomography (CT) machines are now capable of high-resolution images of rectal cancer and utilized for CT perfusion. The possibility of local staging of rectal cancer by CT needs to be explored.

Purpose The aim of the study is to evaluate accuracy of high-resolution CT for local rectal cancer staging.

Methods A high-resolution CT was performed for local staging of rectal cancer in our study group of 93 patients, where 64 underwent primary surgery and 29 underwent surgery post neoadjuvant chemoradiotherapy (NACRT).

Results In differentiating stages T2-and-less than T2 from T3–T4 rectal cancer, accuracy, sensitivity, specificity, and kappa score in overall patients were 91%, 87%, 94%, and 0.8; in primary surgery group were 89%, 76%, 94%, and 0.7; in NACRT group were 97%, 100%, 94%, and 0.9; in low rectal group were 94%, 89%, 97%, and 0.82, respectively.

Conclusion High resolution CT is an accurate tool for local staging of rectal cancer.

Machine Learning-Based Radiomics Nomogram for Detecting Extramural Venous Invasion in Rectal Cancer

Objective

To establish and validate a radiomics nomogram based on the features of the primary tumor for predicting preoperative pathological extramural venous invasion (EMVI) in rectal cancer using machine learning.

Methods

The clinical and imaging data of 281 patients with primary rectal cancer from April 2012 to May 2018 were retrospectively analyzed. All the patients were divided into a training set (n = 198) and a test set (n = 83) respectively. The radiomics features of the primary tumor were extracted from the enhanced computed tomography (CT), the T2-weighted imaging (T2WI) and the gadolinium contrast-enhanced T1-weighted imaging (CE-TIWI) of each patient. One optimal radiomics signature extracted from each modal image was generated by receiver operating characteristic (ROC) curve analysis after dimensionality reduction. Three kinds of models were constructed based on training set, including the clinical model (the optimal radiomics signature combining with the clinical features), the magnetic resonance imaging model (the optimal radiomics signature combining with the mrEMVI status) and the integrated model (the optimal radiomics signature combining with both the clinical features and the mrEMVI status). Finally, the optimal model was selected to create a radiomics nomogram. The performance of the nomogram to evaluate clinical efficacy was verified by ROC curves and decision curve analysis curves.

Results

The radiomics signature constructed based on T2WI showed the best performance, with an AUC value of 0.717, a sensitivity of 0.742 and a specificity of 0.621. The radiomics nomogram had the highest prediction efficiency, of which the AUC was 0.863, the sensitivity was 0.774 and the specificity was 0.801.

Conclusion

The radiomics nomogram had the highest efficiency in predicting EMVI. This may help patients choose the best treatment strategy and may strengthen personalized treatment methods to further optimize the treatment effect.

Application of ultrasound in the diagnosis of gastrointestinal tumors

Gastrointestinal tumors are common tumors in the digestive system. Early diagnosis of gastrointestinal tumors is the key to improve prognosis and curative effect of patients with tumors. Compared with other methods of examination and diagnosis, ultrasound examination has the advantages of simple operation, non-invasive, economical, and repeatable operation. With the advancement of ultrasound technology and the development of ultrasound contrast agents, ultrasound examination is more and more applied to gastrointestinal examination. Ultrasound cannot only observe the gastrointestinal wall, but also evaluate the surrounding lesions and metastases, as well as preoperative analysis and postoperative follow-up of gastrointestinal tumors. We reviewed the diagnostic applications of ultrasound in gastrointestinal tumors.

Radiological staging of rectal cancer in a resource limited setting

Objective

Current guidelines on rectal cancer (RC) management recommend pre-operative MRI for loco-regional staging and CT for staging of metastases. This allows appropriate selection of patients for chemo-radiotherapy (CRT). However, MRI is not freely available in many low-income countries. We assessed the status of pre-operative imaging for RC in Sri Lanka and evaluated the performance of CT in RC staging.

Results

A pre-tested interview-administered questionnaire was used to assess the pre-operative use of MRI and CT in RC. CT findings from 37 RC patients were then compared with histopathology findings. Of the 64 surgeons interviewed, 57 (89.1%) did not request an MRI for their RC patients. Reasons cited included limited availability and long waiting times due to competing health needs. A CT was requested by all. In RC, the overall accuracy of CT for T staging was 43.2% and 29.7% of T1–T2 tumours were over-staged as T3. The overall accuracy of CT for regional lymph node staging was 70.3%. In summary, CT alone is not suitable for RC staging in any setting. It leads to over-staging and patients may thus receive unnecessary CRT. Steps must be taken to improve access to pre-operative MRI among Sri Lankan RC patients.

Imaging and Management of Rectal Cancer

High-resolution phased array external magnetic resonance imaging (MRI) is the first investigation of choice in rectal cancer for local staging, both in the primary and restaging situations. Use of MRI helps differentiate between those with good prognosis, which can be offered upfront surgery and the poor prognostic cases where treatment intensification is needed. MRI identified poor prognostic factors are threatened or involved mesorectal fascia, T3 tumors with >5 mm extramural spread, those with extramural vascular invasion, pelvic sidewall nodes and mucinous tumors. At restaging, use of MRI helps evaluate response and an MR tumor regression grading system is being evaluated. Complete response seen on clinical examination and endoscopy, needs confirmation on MRI using both T2-weighted and diffusion-weighted sequences to justify a "watch and wait" approach. In this subset of patients, MRI also plays a role in monitoring and detecting early regrowth. In those with partial response, MRI helps define surgical margins and can be used as a roadmap to decide between sphincter preserving surgeries and radical sphincter sacrificing surgeries; pelvic exenteration and pelvic sidewall lymph node dissection. Poor responders on MRI may benefit from adjuvant chemotherapy. Use of MRI thus helps in individualizing treatment in rectal cancer.

The clinical application value of multi-slice spiral CT enhanced scans combined with multiplanar reformations images in preoperative T staging of rectal cancer

This study aims to evaluate the diagnostic accuracy and clinical application value of multi-slice spiral CT (MSCT) enhanced scans combined with multiplanar reformations (MPRs) images compared with postoperative pathological results in preoperative T staging of rectal cancer.One hundred sixty-eight consecutive patients with rectal cancer were admitted in our hospital between January 2013 and October 2018. Conventional MSCT plain scans, multi-phase dynamic contrast-enhanced scans, and MPRs were performed in all patients before surgical operation. The preoperative T staging of the rectal cancer lesions was evaluated using MSCT enhanced scans combined with MPRs, which was verified by postoperative pathological results. The diagnostic accuracy of MSCT enhanced scans combined with MPRs in evaluating T staging of the rectal cancer lesions were analyzed by χ test and Kappa test.Compared with postoperative pathology, T staging using MSCT enhanced scans combined with MPRs had overall accuracy of 85.7%. Consistency between MSCT enhanced scans combined with MPRs and postoperative pathological staging was effective for T staging (Kappa = 0.658, χ = 4.200, P = .122).Conventional MSCT enhanced scans combined with MPRs are simple and feasible. It is consistent with the pathological diagnosis of evaluating T staging in the rectal cancer lesions. It can provide reliable imaging evidence for the preoperative evaluation of primary rectal cancer, especially in patients with magnetic resonance imaging (MRI) contraindications, or in grass-roots hospitals due to lack of MRI equipment.

Diagnostic value of fourth-generation iterative reconstruction algorithm with low-dose CT protocol in assessment of mesorectal fascia invasion in rectal cancer: comparison with magnetic resonance

PURPOSE

The purpose of the article is to compare the diagnostic performance about radiation dose and image quality of low-dose CT with iterative reconstruction algorithm (iDose4) and standard-dose CT in the assessment of mesorectal fascia (MRF) invasion in rectal cancer patients.

MATERIALS AND METHODS

Ninety-one patients with biopsy-proven primary rectal adenocarcinoma underwent CT staging: 42 underwent low-dose CT, 49 underwent standard CT protocol. Low-dose contrast-enhanced MDCT scans were performed on a 256 (ICT, Philips) scanner using 120 kV, automated mAs modulation, iDose4 iterative reconstruction algorithm. Standard-dose MDCT scans were performed on the same scanner with 120 kV, 200-300 mAs. All patients underwent a standard lower abdomen MR study (on 1.5T magnet), including multiplanar sequences, considered as reference standard. Diagnostic accuracy of MRF assessment was determined on CT images for both CT protocols and compared with MRI images. Dose-length product (DLP) and CT dose index (CTDI) calculated for both groups were compared and statistically analyzed.

RESULTS

Low-dose protocol with iDose4 showed high diagnostic quality in assessment of MRF with significant reduction (23%; p = 0.0081) of radiation dose (DLP 2453.47) compared to standard-dose examination (DLP 3194.32).

CONCLUSIONS

Low-dose protocol combined with iDose4 reconstruction algorithm offers high-quality images, obtaining significant radiation dose reduction, useful in the evaluation of MRF involvement in rectal cancer patients.