MRI in T staging of rectal cancer: How effective is it?

IPNet: An Interpretable Network With Progressive Loss for Whole-Stage Colorectal Disease Diagnosis

Colorectal cancer plays a dominant role in cancer-related deaths, primarily due to the absence of obvious early-stage symptoms. Whole-stage colorectal disease diagnosis is crucial for assessing lesion evolution and determining treatment plans. However, locality difference and disease progression lead to intra-class disparities and inter-class similarities for colorectal lesion representation. In addition, interpretable algorithms explaining the lesion progression are still lacking, making the prediction process a "black box". In this paper, we propose IPNet, a dual-branch interpretable network with progressive loss for whole-stage colorectal disease diagnosis. The dual-branch architecture captures unbiased features representing diverse localities to suppress intra-class variation. The progressive loss function considers inter-class relationship, using prior knowledge of disease evolution to guide classification. Furthermore, a novel Grain-CAM is designed to interpret IPNet by visualizing pixel-wise attention maps from shallow to deep layers, providing regions semantically related to IPNet's progressive classification. We conducted whole-stage diagnosis on two image modalities, i.e., colorectal lesion classification on 129,893 endoscopic optical images and rectal tumor T-staging on 11,072 endoscopic ultrasound images. IPNet is shown to surpass other state-of-the-art algorithms, accordingly achieving an accuracy of 93.15% and 89.62%. Especially, it establishes effective decision boundaries for challenges like polyp vs. adenoma and T2 vs. T3. The results demonstrate an explainable attempt for colorectal lesion classification at a whole-stage level, and rectal tumor T-staging by endoscopic ultrasound is also unprecedentedly explored. IPNet is expected to be further applied, assisting physicians in whole-stage disease diagnosis and enhancing diagnostic interpretability.

Pixel to Pathology: A Prospective Cross-Sectional Study on the Role of Multidetector Computed Tomography in the Evaluation of Malignant Large Bowel Lesions With Histopathological Correlation

BACKGROUND AND OBJECTIVES

Colorectal lesions can present as a mass or as focal or diffuse thickening of the colon wall and may also be associated with abnormalities in the perienteric region. Multidetector computed tomography (MDCT) enables simultaneous imaging of both extracolonic structures and the gut wall. It is instrumental in assessing tumor extent, detecting pericolic dissemination, including lymph node involvement, and identifying metastases. This study aims to evaluate the role of MDCT in diagnosing large bowel lesions in patients referred from the surgery department with suspected large bowel pathology and to correlate MDCT findings with histopathological results.

MATERIALS AND METHODS

In the Department of Radiodiagnosis at Mahatma Gandhi Medical College and Research Institute (MGMCRI), Pondicherry, this study was carried out from February 2023 to January 2024 over a one-year span. CT imaging was carried out utilizing a GE Optima 128 Slice MDCT scanner for instances of clinically suspected large bowel pathology. IV contrast, rectal, oral (positive), and plain CT were the imaging protocols that were used.

RESULTS

Thirty of the 45 patients were female, and 15 were male; most of the patients were in the 46-60 age range. Twenty-three of the 24 instances with a CT diagnosis of malignancy had a histological confirmation. On CT, all 21 benign lesions were correctly detected. Benign lesions showed homogenous attenuation, mild symmetric wall thickening, and diffuse bowel involvement. Heterogeneous attenuation, pronounced asymmetric wall thickening, and localized bowel involvement were observed in malignant lesions.

CONCLUSION

For the diagnosis and differentiation of benign from malignant colon and rectum lesions, MDCT has shown itself to be an excellent technique. MDCT provides additional information about related pericolic abnormalities, lymph node presence, neighboring organ infiltration, and distant metastases in addition to identifying the lesions.

Study of Comparison of Magnetic Resonance Imaging with Surgical and Pathological features in Carcinoma Rectum Patients

Colorectal cancer is the second-most common cancer in the females and third-most common cancer in males worldwide and it is the second-most common cause of mortality. In India, colorectal cancer is the fifth-most common cancer overall, constituting 6.3%. With the advent of high-resolution magnetic resonance imaging (MRI), it has become the investigation of choice for local staging of rectal cancers as well as in predicting the response to neoadjuvant treatment and streamlining the management. The aims and objectives of this study were to compare the results of MRI with surgicopathological findings in carcinoma (Ca) rectum patients in Indian patients from a tertiary regional Cancer care centre. An observational retrospective study was carried out in the Department of Surgical Oncology Acharya Harihar Regional Cancer Centre, Cuttack, from January 2021 to June 2022. All the patients who were admitted and planned for the definitive surgery for Ca Rectum and Recto sigmoid Ca were included in the study. A total of 68 patients were included, including both upfront and post-neoadjuvant treatment cases. All the patients who received neoadjuvant treatment underwent an MRI for local staging. The findings of MRI were compared with surgical and histopathology results. Results were compared in terms of T staging, N staging and response to neoadjuvant therapy among MRI and surgical and pathological findings. Overall, there was good agreement between MRI and operative findings and histopathological findings.

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.

Contemporary view to the principles of rectal cancer diagnostics and treatment according to MRI (literature review)

In this article are reviewed the most recent diagnostic methods for patients with probable and verified rectal cancer, in different stages of treatment. The importance of high quality visualization of rectal cancer, opportunities of magnetic resonance imaging in primary diagnosis and restaging of the disease after neoadjuvant chemotherapy, optimal examination methods and interpretation of images in routine are discussed.

Has the role of EUS in rectal cancer staging changed in the last decade?

The need for effective diagnosis, staging, and treatment of rectal cancer cannot be overstated. Accurate staging of rectal cancer has wide-ranging implications, including therapeutic strategy and prognosis. A change in stage may lead to the need for preoperative neoadjuvant therapy to decrease the risk of recurrence. The modalities commonly used for the primary staging of rectal cancer include EUS, computed tomography, and magnetic resonance imaging. EUS may be accompanied by the use of EUS-fine-needle aspiration to provide cytological confirmation. In this review, we take a deeper look into the role of EUS in the accurate staging of rectal cancer, how it compares to other modalities for the same, and how its role has changed in the last decade.

Evaluation of endorectal ultrasound (ERUS) and MRI for prediction of circumferential resection margin (CRM) for rectal cancer

ERUS and MRI are used for preoperative imaging of rectal cancer. Here, we compare ERUS and MRI for accuracy of CRM prediction at mid- and distal rectal locations. In retrospective review, 20 rectal cancer patients having TME surgery had both ERUS and MRI preoperatively: 8 mid rectum and 12 in distal rectum. Predicted CRM by ERUS and MRI were compared to TME pathology. Overall, predicted CRM was 6.5 ± 3.6 mm by ERUS, 7.7 ± 5.0 mm by MRI, and 6.0 ± 4.6 mm by pathology. Overall, correlation coefficients to pathology were 0.77 (p = 0.0004) for ERUS and 0.64 (p = 0.008) for MRI. In distal rectum, correlation coefficients were 0.71 (p = 0.02) for ERUS and -0.10 (p = 0.79) for MRI. In mid rectum, correlation coefficients were 0.92 (p = 0.01) for ERUS and 0.44 (p = 0.38) for MRI. While MRI is used routinely for preoperative rectal cancer imaging, ERUS can provide additional assessment of CRM for mid or distal rectal lesions. Further investigation is needed to support these preliminary ERUS CRM findings in mid and distal rectum.

The value of high-resolution MRI technique in patients with rectal carcinoma: pre-operative assessment of mesorectal fascia involvement, circumferential resection margin and local staging

Background

The purpose of the study was to identify the accuracy of high-resolution MRI in the pre-operative assessment of mesorectal fascia involvement, circumfrential resection margin (CRM) and local staging in patients with rectal carcinoma.

Material/Methods

The study included 56 patients: 32 male and 24 female. All patients underwent high-resolution MRI and had confirmed histopathological diagnosis of rectal cancer located within 15 cm from the anal verge, followed by surgery. MRI findings were compared with pathological and surgical results.

Results

The overall accuracy, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of MRI-based T-staging were 92.8, 88.8%, 96.5%, 96%, and 90.3%, respectively. The accuracy, sensitivity, specificity, PPV, and NPV of MRI-based assessment of CRM were 94.6%, 84.6%, 97.6%, 91.4, and 94.6%, respectively. The accuracy, sensitivity, specificity, PPV, and NPV of MRI-based N-staging were 82.1%, 75%, 67.3%, 60%, and 86.1%, respectively.

Conclusions

Preoperative high-resolution rectal MRI is accurate in predicting tumor stage and CRM involvement. MRI is a precise diagnostic tool to select patients who may benefit from neo-adjuvant therapy and to avoid overtreatment in those patients who can proceed directly to surgery.

Clinical significance of magnetic resonance imaging findings in rectal cancer

Staging of rectal cancer is essential to help guide clinicians to decide upon the correct type of surgery and determine whether or not neoadjuvant therapy is indicated. Magnetic resonance imaging (MRI) is currently one of the most accurate modalities on which to base treatment decisions for patients with rectal cancer. MRI can accurately detect the mesorectal fascia, assess the invasion of the mesorectum or surrounding organs and predict the circumferential resection margin. Although nodal disease remains a difficult radiological diagnosis, new lymphographic agents and diffusion weighted imaging may allow identification of metastatic nodes by criteria other then size. In light of this, we have reviewed the literature on the accuracy of specific MRI findings for staging the local extent of primary rectal cancer. The aim of this review is to establish a correlation between MRI findings, prognosis, and available treatment options.

Benefits and challenges in bowel MR imaging at 3.0 T

Abdominal imaging at 3.0 T has shown to be challenging because of a number of artifacts and effects related to the physics at higher field strength. For bowel imaging at 3.0 T, artifacts due to magnetic field inhomogeneities, standing waves, increased susceptibility, and greater chemical shift effects are of particular concern because they are likely to affect the assessment of relevant structures and counterbalance the benefits of higher signal-to-noise ratio. Regarding small- and large-bowel magnetic resonance imaging, the benefits of higher field strengths translate mainly in better contrast-to-noise ratio of contrast-enhanced T1-weighted gradient echo and T2-weighted imaging, whereas steady-state free precession sequences seem to suffer from serious degradation of image quality. The present article summarizes the technical challenges in bowel imaging at 3.0 T, provides an overview of performance compared with 1.5 T in small- and large-bowel diseases including the rectum, and revises the current literature.