T-staging of rectal cancer: accuracy of 3.0 Tesla MRI compared with 1.5 Tesla

Watch & wait - Post neoadjuvant imaging for rectal cancer

Rectal cancer management has evolved over the past decade with the emergence of total neoadjuvant therapy (TNT). For select patients who achieve a clinical complete response following TNT, organ preservation by means of the watch-and-wait (WW) strategy is an increasingly adopted alternative that preserves rectal function and quality of life without compromising oncologic outcomes. Recently, published 5-year results from the OPRA trial demonstrated that organ preservation can be achieved in approximately half of patients managed with the WW strategy, with most local regrowth events occurring within two years. Considering the potential for local regrowth, the implementation of the WW strategy mandates rigorous clinical and radiographic surveillance. Magnetic resonance imaging (MRI) serves as the conventional imaging modality for local staging and surveillance of rectal cancer given its excellent soft-tissue resolution. This review will discuss the current evidence for the WW strategy and the role of restaging rectal MRI in determining patient eligibility for this strategy. Restaging rectal MRI acquisition parameters and treatment response assessment, including important factors to assess, pitfalls, and classification systems, will be discussed in the context of the WW strategy.

Prediction of pathologic complete response to neoadjuvant chemoradiation in locally advanced rectal cancer

Purpose

To investigate the predictive factors of pathologic complete response (pCR) in locally advanced rectal cancer (LARC) patients who had been treated with neoadjuvant chemoradiation (nCRT).

Methods and materials

For this retrospective study, 53 LARC patients (37 males and 16 females; age range 25 to 79 years) were selected. Clinical characteristics, baseline mrTNM staging, MR gross tumor volumes (GTV), and pCR were evaluated. The diagnostic accuracy of GTV for predicting pCR was calculated.

Results

Among 53 LARC patients, 15 patients achieved pCR (28.3%), while 38 patients achieved non-pCR. Only three (5.7%) out of 53 patients did not downstage after nCRT. GTV and tumor differentiation were the significant prognostic parameters for predicting pCR. A tumor volume threshold of 21.1 cm3 was determined as a predictor for pCR, with a sensitivity of 84% and specificity of 47%. In addition, GTV was associated with mrN stage, circumferential resection margin (CRM) status, extramural vascular invasion (EMVI) status, and pretreatment serum CEA level.

Conclusion

Tumor volume and tumor differentiation have significant predictive values in preoperative assessment of pCR among LARC patients. These findings aid clinicians to discriminate those patients who may likely benefit from preoperative regimens and to make optimal treatment plans.

Deep Learning-Based Multiparametric MRI Model for Preoperative T-Stage in Rectal Cancer

BACKGROUND

Conventional MRI staging can be challenging in the preoperative assessment of rectal cancer. Deep learning methods based on MRI have shown promise in cancer diagnosis and prognostication. However, the value of deep learning in rectal cancer T-staging is unclear.

PURPOSE

To develop a deep learning model based on preoperative multiparametric MRI for evaluation of rectal cancer and to investigate its potential to improve T-staging accuracy.

STUDY TYPE

Retrospective.

POPULATION

After cross-validation, 260 patients (123 with T-stage T1-2 and 134 with T-stage T3-4) with histopathologically confirmed rectal cancer were randomly divided to the training (N = 208) and test sets (N = 52).

FIELD STRENGTH/SEQUENCE

3.0 T/Dynamic contrast enhanced (DCE), T2-weighted imaging (T2W), and diffusion-weighted imaging (DWI).

ASSESSMENT

The deep learning (DL) model of multiparametric (DCE, T2W, and DWI) convolutional neural network were constructed for evaluating preoperative diagnosis. The pathological findings served as the reference standard for T-stage. For comparison, the single parameter DL-model, a logistic regression model composed of clinical features and subjective assessment of radiologists were used.

STATISTICAL TESTS

The receiver operating characteristic curve (ROC) was used to evaluate the models, the Fleiss' kappa for the intercorrelation coefficients, and DeLong test for compare the diagnostic performance of ROCs. P-values less than 0.05 were considered statistically significant.

RESULTS

The Area Under Curve (AUC) of the multiparametric DL-model was 0.854, which was significantly higher than the radiologist's assessment (AUC = 0.678), clinical model (AUC = 0.747), and the single parameter DL-models including T2W-model (AUC = 0.735), DWI-model (AUC = 0.759), and DCE-model (AUC = 0.789).

DATA CONCLUSION

In the evaluation of rectal cancer patients, the proposed multiparametric DL-model outperformed the radiologist's assessment, the clinical model as well as the single parameter models. The multiparametric DL-model has the potential to assist clinicians by providing more reliable and precise preoperative T staging diagnosis.

EVIDENCE LEVEL

3 TECHNICAL EFFICACY: Stage 2.

Risk Factors for Distant Metastasis in T3 T4 Rectal Cancer

Background

Distant metastasis is the leading cause of death in patients with rectal cancer. This study aims to comprehensively analyze the risk factors of distant metastasis in T3 T4 rectal cancer using magnetic resonance imaging (MRI), pathological features, and serum indicators.

Methods

The clinicopathological data of 146 cases of T3 T4 rectal cancer after radical resection from January 2015 to March 2023 were retrospectively analyzed. Pre- and postoperative follow-up data of all cases were collected to screen for distant metastatic lesions. Univariate and multivariate Logistic regression methods were used to analyze the relationship between MRI features, pathological results, serum test indexes, and distant metastasis.

Results

Of the 146 included patients, synchronous or metachronous distance metastasis was confirmed in 43 (29.4%) cases. The patients' baseline data and univariate analysis showed that mrEMVI, maximum tumor diameter, mr T Stage, pathological N stage, number of lymph node metastasis, cancer nodules, preoperative serum CEA, (Carcinoembryonic antigen) and CA199 were associated with distant metastasis. In the multiple logistic regression model, mrEMVI, pathological N stage, number of lymph node metastasis, maximum tumor diameter, and preoperative serum CEA were identified as independent risk factors for distant metastasis: mrEMVI [odds ratio (OR) = 3.06], pathological N stage (OR = 6.52 for N1 vs N0; OR = 63.47 for N2 vs N0), preoperative serum CEA (OR = 0.27), tumor maximum diameter (OR = 1.03), number of lymph nodes metastasis (OR = 0.62). And, the receiver operating characteristic (ROC) curve was plotted and the area under the curve was calculated (area under the curve [AUC) = 0.817, 95% CI = 0.744-0.890, P < .001].

Conclusions

mrEMVI, pathological N stage, number of lymph node metastasis, maximum tumor diameter and preoperative serum CEA are the independent risk factors for distant metastasis in T3 T4 rectal cancer. A comprehensive analysis of the risk factors for distant metastasis in rectal cancer can provide a reliable basis for formulating individualized treatment strategies, follow-up plans, and evaluating prognosis.

PET/MRI in colorectal and anal cancers: an update

Positron emission tomography (PET) in the era of personalized medicine has a unique role in the management of oncological patients and offers several advantages over standard anatomical imaging. However, the role of molecular imaging in lower GI malignancies has historically been limited due to suboptimal anatomical evaluation on the accompanying CT, as well as significant physiological 18F-flurodeoxyglucose (FDG) uptake in the bowel. In the last decade, technological advancements have made whole-body FDG-PET/MRI a feasible alternative to PET/CT and MRI for lower GI malignancies. PET/MRI combines the advantages of molecular imaging with excellent soft tissue contrast resolution. Hence, it constitutes a unique opportunity to improve the imaging of these cancers. FDG-PET/MRI has a potential role in initial diagnosis, assessment of local treatment response, and evaluation for metastatic disease. In this article, we review the recent literature on FDG-PET/MRI for colorectal and anal cancers; provide an example whole-body FDG-PET/MRI protocol; highlight potential interpretive pitfalls; and provide recommendations on particular clinical scenarios in which FDG-PET/MRI is likely to be most beneficial for these cancer types.

Deep learning models for preoperative T-stage assessment in rectal cancer using MRI: exploring the impact of rectal filling

Background

The objective of this study was twofold: firstly, to develop a convolutional neural network (CNN) for automatic segmentation of rectal cancer (RC) lesions, and secondly, to construct classification models to differentiate between different T-stages of RC. Additionally, it was attempted to investigate the potential benefits of rectal filling in improving the performance of deep learning (DL) models.

Methods

A retrospective study was conducted, including 317 consecutive patients with RC who underwent MRI scans. The datasets were randomly divided into a training set (n = 265) and a test set (n = 52). Initially, an automatic segmentation model based on T2-weighted imaging (T2WI) was constructed using nn-UNet. The performance of the model was evaluated using the dice similarity coefficient (DSC), the 95th percentile Hausdorff distance (HD95), and the average surface distance (ASD). Subsequently, three types of DL-models were constructed: Model 1 trained on the total training dataset, Model 2 trained on the rectal-filling dataset, and Model 3 trained on the non-filling dataset. The diagnostic values were evaluated and compared using receiver operating characteristic (ROC) curve analysis, confusion matrix, net reclassification index (NRI), and decision curve analysis (DCA).

Results

The automatic segmentation showed excellent performance. The rectal-filling dataset exhibited superior results in terms of DSC and ASD (p = 0.006 and 0.017). The DL-models demonstrated significantly superior classification performance to the subjective evaluation in predicting T-stages for all test datasets (all p < 0.05). Among the models, Model 1 showcased the highest overall performance, with an area under the curve (AUC) of 0.958 and an accuracy of 0.962 in the filling test dataset.

Conclusion

This study highlighted the utility of DL-based automatic segmentation and classification models for preoperative T-stage assessment of RC on T2WI, particularly in the rectal-filling dataset. Compared with subjective evaluation, the models exhibited superior performance, suggesting their noticeable potential for enhancing clinical diagnosis and treatment practices.

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.

In vivo study of cone beam computed tomography texture analysis of mandibular condyle and its correlation with gender and age

OBJECTIVE

Texture analysis is an image processing method that aims to assess the distribution of gray-level intensity and spatial organization of the pixels in the image. The purpose of this study was to investigate whether the texture analysis applied to cone beam computed tomography (CBCT) images could detect variation in the condyle trabecular bone of individuals from different age groups and genders.

METHODS

The sample consisted of imaging exams from 63 individuals divided into three groups according to age groups of 03-13, 14-24 and 25-34. For texture analysis, the MaZda^® software was used to extract the following parameters: second angular momentum, contrast, correlation, sum of squares, inverse difference moment, sum entropy and entropy. Statistical analysis was performed using Mann-Whitney test for gender and Kruskal-Wallis test for age (P = 5%).

RESULTS

No statistically significant differences were found between age groups for any of the parameters. Males had lower values for the parameter correlation than those of females (P < 0.05).

CONCLUSION

Texture analysis proved to be useful to discriminate mandibular condyle trabecular bone between genders.

Deep-learning-based 3D super-resolution MRI radiomics model: superior predictive performance in preoperative T-staging of rectal cancer

OBJECTIVES

To investigate the feasibility and efficacy of a deep-learning (DL)-based three-dimensional (3D) super-resolution (SR) MRI radiomics model for preoperative T-staging prediction in rectal cancer (RC).

METHODS

Seven hundred six eligible RC patients (T1/2 = 287, T3/4 = 419) were retrospectively enrolled in this study and chronologically allocated into a training cohort (n = 565) and a validation cohort (n = 141). We conducted a deep-transfer-learning network on high-resolution (HR) T2-weighted imaging (T2WI) to enhance the z-resolution of the images and acquired the preoperative SRT2WI. The radiomics models named model_HRT2 and model_SRT2 were respectively constructed with high-dimensional quantitative features extracted from manually segmented volume of interests of HRT2WI and SRT2WI through the Least Absolute Shrinkage and Selection Operator method. The performances of the models were evaluated by ROC, calibration, and decision curves.

RESULTS

Model_SRT2 outperformed model_HRT2 (AUC 0.869, sensitivity 71.1%, specificity 93.1%, and accuracy 83.3% vs. AUC 0.810, sensitivity 89.5%, specificity 70.1%, and accuracy 77.3%) in distinguishing T1/2 and T3/4 RC with significant difference (p < 0.05). Both radiomics models achieved higher AUCs than the expert radiologists (0.685, 95% confidence interval 0.595-0.775, p < 0.05). The calibration curves confirmed high goodness of fit, and the decision curve analysis revealed the clinical value.

CONCLUSIONS

Model_SRT2 yielded superior predictive performance in preoperative RC T-staging by comparison with model_HRT2 and expert radiologists' visual assessments.

KEY POINTS

• For the first time, DL-based 3D SR images were applied in radiomics analysis for clinical utility. • Compared with the visual assessment of expert radiologists and the conventional radiomics model based on HRT2WI, the SR radiomics model showed a more favorable capability in helping clinicians assess the invasion depth of RC preoperatively. • This is the largest radiomics study for T-staging prediction in RC.

ACR Appropriateness Criteria® Staging of Colorectal Cancer: 2021 Update

Preoperative imaging of rectal carcinoma involves accurate assessment of the primary tumor as well as distant metastatic disease. Preoperative imaging of nonrectal colon cancer is most beneficial in identifying distant metastases, regardless of primary T or N stage. Surgical treatment remains the definitive treatment for colon cancer, while organ-sparing approach may be considered in some rectal cancer patients based on imaging obtained before and after neoadjuvant treatment. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Lymph Nodes Evaluation in Rectal Cancer: Where Do We Stand and Future Perspective

The assessment of nodal involvement in patients with rectal cancer (RC) is fundamental in disease management. Magnetic Resonance Imaging (MRI) is routinely used for local and nodal staging of RC by using morphological criteria. The actual dimensional and morphological criteria for nodal assessment present several limitations in terms of sensitivity and specificity. For these reasons, several different techniques, such as Diffusion Weighted Imaging (DWI), Intravoxel Incoherent Motion (IVIM), Diffusion Kurtosis Imaging (DKI), and Dynamic Contrast Enhancement (DCE) in MRI have been introduced but still not fully validated. Positron Emission Tomography (PET)/CT plays a pivotal role in the assessment of LNs; more recently PET/MRI has been introduced. The advantages and limitations of these imaging modalities will be provided in this narrative review. The second part of the review includes experimental techniques, such as iron-oxide particles (SPIO), and dual-energy CT (DECT). Radiomics analysis is an active field of research, and the evidence about LNs in RC will be discussed. The review also discusses the different recommendations between the European and North American guidelines for the evaluation of LNs in RC, from anatomical considerations to structured reporting.

Overview of the Large Bowel Assessment Using Magnetic Resonance Imaging: Different Techniques for Current and Emerging Clinical Applications

Radiological assessments of the small and large bowel are essential in daily clinical practice. Over plain film X-ray and ultrasound, cross-sectional techniques are considered the most comprehensive imaging modalities. In fact, computed tomography and magnetic resonance imaging take great advantage of the three-dimensional appraisal and the extensive evaluation of the abdominal cavity, allowing intestinal evaluation as well as detection of extra-intestinal findings. In this context, the chief advantage of computed tomography is the fast scan time, which is crucial for emergency cases. Nonetheless, it is undeniably impaired using ionizing radiation. As the awareness of radiation exposure is a topic of increasing importance, magnetic resonance imaging is not only becoming a mere alternative but also a primary imaging technique used in assessing intestinal diseases. Specifically, the evaluation of the large bowel through MRI can be still considered relatively uncharted territory. Although it has demonstrated superior accuracy in the assessment of some clinical entities from inflammatory bowel disease to rectal carcinoma, its role needs to be consolidated in many other conditions. Moreover, different technical methods can be applied for colonic evaluation depending on the specific disease and segment involved. This article aims to provide a thorough overview of the techniques that can be utilized in the evaluation of the large bowel and a discussion on the major findings in different colonic pathologies of primary interest.

Added value of quantitative, multiparametric 18F-FDG PET/MRI in the locoregional staging of rectal cancer

PURPOSE

The purpose of this study was to determine whether multiparametric positron emission tomography/magnetic resonance imaging (mpPET/MRI) can improve locoregional staging of rectal cancer (RC) and to assess its prognostic value after resection.

METHODS

In this retrospective study, 46 patients with primary RC, who underwent multiparametric 18F-fluorodeoxyglucose (FDG) PET/MRI, followed by surgical resection without chemoradiotherapy, were included. Two readers reviewed T- and N- stage, mesorectal involvement, sphincter infiltration, tumor length, and distance from anal verge. In addition, diffusion-weighted imaging (DWI) and PET parameters were extracted from the multiparametric protocol and were compared to radiological staging as well as to the histopathological reference standard. Clinical and imaging follow-up was systematically assessed for tumor recurrence and death.

RESULTS

Locally advanced rectal cancers (LARC) exhibited significantly higher metabolic tumor volume (MTV, AUC 0.74 [95% CI 0.59-0.89], p = 0.004) and total lesion glycolysis (TLG, AUC 0.70 [95% CI 0.53-0.87], p = 0.022) compared to early tumors. T-stage was associated with MTV (AUC 0.70 [95% CI 0.54-0.85], p = 0.021), while N-stage was better assessed using anatomical MRI sequences (AUC 0.72 [95% CI 0.539-0.894], p = 0.032). In the multivariate regression analysis, depending on the model, both anatomical MRI sequences and MTV/TLG were capable of detecting LARC. Combining anatomical MRI stage and MTV/TLG led to a superior diagnostic performance for detecting LARC (AUC 0.81, [95% CI 0.68-0.94], p &lt; 0.001). In the survival analysis, MTV was independently associated with overall survival (HR 1.05 [95% CI 1.01-1.10], p = 0.044).

CONCLUSION

Multiparametric PET-MRI can improve identification of locally advanced tumors and, hence, help in treatment stratification. It provides additional information on RC tumor biology and may have prognostic value.

Evolutions in rectal cancer MRI staging and risk stratification in The Netherlands

Purpose

To analyze how the MRI reporting of rectal cancer has evolved (following guideline updates) in The Netherlands.

Methods

Retrospective analysis of 712 patients (2011–2018) from 8 teaching hospitals in The Netherlands with available original radiological staging reports that were re-evaluated by a dedicated MR expert using updated guideline criteria. Original reports were classified as “free-text,” “semi-structured,” or “template” and completeness of reporting was documented. Patients were categorized as low versus high risk, first based on the original reports (high risk = cT3-4, cN+, and/or cMRF+) and then based on the expert re-evaluations (high risk = cT3cd-4, cN+, MRF+, and/or EMVI+). Evolutions over time were studied by splitting the inclusion period in 3 equal time periods.

Results

A significant increase in template reporting was observed (from 1.6 to 17.6–29.6%; p < 0.001), along with a significant increase in the reporting of cT-substage, number of N+ and extramesorectal nodes, MRF invasion and tumor-MRF distance, EMVI, anal sphincter involvement, and tumor morphology and circumference. Expert re-evaluation changed the risk classification from high to low risk in 18.0% of cases and from low to high risk in 1.7% (total 19.7%). In the majority (17.9%) of these cases, the changed risk classification was likely (at least in part) related to use of updated guideline criteria, which mainly led to a reduction in high-risk cT-stage and nodal downstaging.

Conclusion

Updated concepts of risk stratification have increasingly been adopted, accompanied by an increase in template reporting and improved completeness of reporting. Use of updated guideline criteria resulted in considerable downstaging (of mainly high-risk cT-stage and nodal stage).

Graphic abstract

High-Resolution Diffusion-Weighted Imaging for Evaluation of Extramural Tumor Invasion in Primary Rectal Cancer

OBJECTIVE

The aim of this study was to determine the added value of high-resolution diffusion-weighted imaging (DWI) to T2-weighted imaging (T2WI) for evaluation of extramural tumor invasion (EMTI) in patients with primary rectal cancer.

METHODS

Seventy-eight patients who had undergone 3.0-T magnetic resonance imaging including DWI (b = 0, 1000 s/mm2, 2 mm iso-voxel) and subsequent surgery were included. Two blinded radiologists independently read the T2WI first and then the combined DWI set. They recorded their confidence level using a 5-point scale. The diagnostic accuracy was calculated by receiver operating characteristic curve analysis based on the histopathological results as the reference.

RESULTS

The study population consisted of EMTI positive (n = 44) and negative (n = 34). The area under the curve was not significantly increased after adding DWI to T2WI (reader 1, 0.868-0.856, P = 0.5618; reader 2, 0.848-0.865, P = 0.4539).

CONCLUSION

Adding DWI to T2WI showed no additional diagnostic value for the evaluation of EMTI in patients with primary rectal cancer.

Imaging and Diagnosis for Planning the Surgical Procedure

The preoperative imaging diagnosis of rectal cancer lies at the heart of oncological staging and has a crucial influence on patient management and therapy planning. Rectal cancer is common, and accurate preoperative staging of tumors using high-resolution magnetic resonance imaging (MRI) is a crucial part of modern multidisciplinary team management (MDT). Indeed, rectal MRI has the ability to accurately evaluate a number of important findings that maBay impact patient management, including distance of the tumor to the mesorectal fascia, presence of lymph nodes, presence of extramural vascular invasion (EMVI), and involvement of the anterior peritoneal reflection/peritoneum and the sphincter complex. Many of these findings are difficult to assess in non-expert hands. In this chapter, we present currently used staging modalities with focus on MRI, including optimization of imaging techniques, tumor staging, interpretation help as well as essentials for reporting.

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.

T-staging of rectal cancer: Utility of single-shot turbo spin-echo diffusion-weighted imaging with T2-weighted images and fusion images

PURPOSE

The purpose of this study was to evaluate the usefulness of turbo spin-echo (TSE) DWI with fusion images in the T-staging compared with T2-weighted imaging (T2WI) alone and conventional echo-planner imaging (EPI) DWI.

METHODS

In this prospective study, 4-mm-thick axial EPI-DWI, TSE-DWI, and T2WI were performed with the same slice locations for 20 patients with rectal cancer. Fusion images of DWI and T2WI were created for both EPI-DWI and TSE-DWI. Ten readers independently diagnosed the T-stages and scored the degree of confidence referring to T2WI alone and then to DWI, T2WI, and fusion images (DWI+T2WI) for each EPI-DWI and TSE-DWI. Visual score assessments of image quality were performed for each DWI.

RESULTS

Inter-observer agreement of T-staging for 10 readers was slight on T2WI alone but fair on EPI-DWI+T2WI and excellent on TSE-DWI+T2WI images. No readers gave higher confidence scores for T2WI compared to EPI/TSE-DWI+T2WI and for EPI-DWI+T2WI compared to TSE-DWI+T2WI. In seven pathologically-proven cases, poor, poor to slight, and fair to perfect agreements with the pathological T-stage were observed with T2WI alone, EPI-DWI+T2WI, and TSE-DWI+T2WI, respectively. All readers gave higher scores regarding image distortion and lower scores regarding image noise for TSE-DWI compared to EPI-DWI. For DWI utility, higher scores were assigned for TSE-DWI compared to EPI-DWI in 7 readers and there were no significant differences in the other 3 readers.

CONCLUSION

TSE-DWI images might be more appropriate for image fusion with T2WI and rectal cancer T-staging compared with EPI-DWI and T2WI alone.

Assessment of T and N staging with MRI3T in lower and middle rectal cancer and impact on clinical strategy

BACKGROUND

To determine the diagnostic accuracy of preoperative T/N stage using MRI in lower and middle rectal cancer patients and the impacts on clinical decision-making.

PATIENTS AND METHODS

There were 354 patients recruited from May 2017 to February 2019. MRI was performed within 2 weeks before surgery. Histopathologic results were evaluated for the postoperative T/N stage and MRI diagnostic accuracy was assessed based on the postoperative histopathologic results. Accuracy, sensitivity, specificity, positive predictive value, negative predictive value, and Kappa values were used to evaluate MRI diagnostic accuracy and analysis consistency compared with postoperative histopathologic staging.

RESULTS

Overall MRI diagnostic accuracy was 78.2% and 56.8% for T1-4 and N0-2 staging. The Kappa values were 0.625 and 0.323 for T1-4 and N0-2 staging, respectively. After combination, MRI diagnostic accuracy was 85% and 69.5% for T and N staging. The Kappa values were 0.693 and 0.4 for T and N staging. The diagnostic accuracy of MRI for treatment decision-making was 79.1%.

CONCLUSION

MRI enables a highly accurate preoperative assessment of T stage but only a fairly accurate preoperative assessment of the N stage for rectal cancer with surgery. The diagnostic accuracy of MRI for treatment decision-making is promising.

Magnetic Resonance of Rectal Cancer Response to Therapy: An Image Quality Comparison between 3.0 and 1.5 Tesla

Purpose

To evaluate signal intensity (SI) differences between 3.0 T and 1.5 T on T2-weighted (T2w), diffusion-weighted imaging (DWI), and apparent diffusion coefficient (ADC) in rectal cancer pre-, during, and postneoadjuvant chemoradiotherapy (CRT).

Materials and Methods

22 patients with locally advanced rectal cancer were prospectively enrolled. All patients underwent T2w, DWI, and ADC pre-, during, and post-CRT on both 3.0 T MRI and 1.5 T MRI. A radiologist drew regions of interest (ROIs) of the tumor and obturator internus muscle on the selected slice to evaluate SI and relative SI (rSI). Additionally, a subanalysis evaluating the SI before and after-CRT (∆SI pre-post) in complete responder patients (CR) and nonresponder patients (NR) on T2w, DWI, and ADC was performed.

Results

Significant differences were observed for T2w and DWI on 3.0 T MRI compared to 1.5 T MRI pre-, during, and post-CRT (all P < 0.001), whereas no significant differences were reported for ADC among all controls (all P > 0.05). rSI showed no significant differences in all the examinations for all sequences (all P > 0.05). ∆SI showed significant differences between 3.0 T and 1.5 T MRI for DWI-∆SI in CR and NR (188.39 ± 166.90 vs. 30.45 ± 21.73 and 169.70 ± 121.87 vs. 22.00 ± 31.29, respectively, all P 0.02) and ADC-∆SI for CR (−0.58 ± 0.27 vs. −0.21 ± 0.24P value 0.02), while no significant differences were observed for ADC-∆SI in NR and both CR and NR for T2w-∆SI.

Conclusion

T2w-SI and DWI-SI showed significant differences for 3.0 T compared to 1.5 T in all three controls, while ADCSI showed no significant differences in all three controls on both field strengths. rSI was comparable for 3.0 T and 1.5 T MRI in rectal cancer patients; therefore, rectal cancer patients can be assessed both at 3.0 T MRI and 1.5 T MRI. However, a significant DWI-∆SI and ADC-∆SI on 3.0 T in CR might be interpreted as a better visual assessment in discriminating response to therapy compared to 1.5 T. Further investigations should be performed to confirm future possible clinical application.

MRI for Rectal Cancer Primary Staging and Restaging After Neoadjuvant Chemoradiation Therapy: How to Do It During Daily Clinical Practice

PURPOSE

To provide a practical overview regarding the state-of-the-art of the magnetic resonance imaging (MRI) protocol for rectal cancer imaging and interpretation during primary staging and restaging after neoadjuvant chemoradiation therapy (CRT), pointing out technical skills and findings that radiologists should consider for their reports during everyday clinical activity.

METHOD

Both 1.5T and 3.0T scanners can be used for rectal cancer evaluation, using pelvic phased array external coils. The standard MR protocol includes T2-weighted imaging of the pelvis, high-resolution T2-weighted sequences focused on the tumor and diffusion-weighted imaging (DWI). The mnemonic DISTANCE is helpful for the interpretation of MR images: DIS, for distance from the inferior part of the tumor to the anorectal-junction; T, for T staging; A, for anal sphincter complex status; N, for nodal staging; C, for circumferential resection margin status; and E, for extramural venous invasion.

RESULTS

Primary staging with MRI is a cornerstone in the preoperative workup of patients with rectal cancer, because it provides clue information for decisions on the administration of CRT and surgical treatment. Restaging after CRT is crucial for treatment planning, and findings on post-CRT MRI correlate with the patient's prognosis and survival. It may be useful to remember the mnemonic word "DISTANCE" to check and describe all the relevant MRI findings necessary for an accurate radiological definition of tumor stage and response to CRT.

CONCLUSIONS

"DISTANCE" assessment for rectal cancer staging and treatment response estimation after CRT may be helpful as a checklist for a structured reporting.

Value of 3Tesla MRI in the preoperative staging of mid-low rectal cancer and its impact on clinical strategies

Background

To determine the diagnostic accuracy of preoperative T/N stage with magnetic resonance imaging (MRI) in lower and middle rectal cancer patients and the impacts on clinical decision‐making.

Patients and methods

A total of 211 patients were recruited from October 2015 to March 2017 in this retrospective study. High‐resolution MRI was performed within 2 weeks before surgery. Histopathologic results were evaluated for the postoperative T/N stage and the diagnostic accuracy of MRI was assessed according to the postoperative histopathologic results. The accuracy, sensitivity, specificity, positive predictive value and negative predictive value were evaluated for T/N staging and κ values were used to evaluate MRI consistent analysis compared with postoperative histopathologic staging.

Results

The overall MRI diagnostic accuracy was 79.62% for T1‐4 staging and 54.50% for N0‐2 staging. The κ values were 0.619 and 0.255 for T1‐4 and N0‐2 staging, respectively. The diagnostic accuracy of MRI for treatment decision‐making was 80.57%.

Conclusion

MRI allows a highly accurate preoperative assessment of T stage but only a fairly accurate preoperative assessment of N stage for rectal cancer. The diagnostic accuracy of MRI for treatment decision‐making is promising, but additional studies are needed to validate these findings in a larger sample size from multiple centers.

Rectal cancer MR staging: pearls and pitfalls at baseline examination

In recent years, rectal MRI has become a central diagnostic tool in rectal cancer staging. Indeed, rectal MR has the ability to accurately evaluate a number of important findings that may impact patient management, including distance of the tumor to the mesorectal fascia, presence of extramural vascular invasion (EMVI), presence of lymph nodes, and involvement of the peritoneum/anterior peritoneal reflection. Many of these findings are difficult to assess in nonexpert hands. In this review, we present a practical approach for radiologists to provide high-quality interpretations at initial baseline exams, based on recent guidelines from the Society of Abdominal Radiology, Rectal and Anal Cancer Disease Focused Panel. Practical pearls and pitfalls are discussed, focusing on optimization of technique including, patient preparation and protocol recommendations, interpretation, and essentials of reporting.

Differences in prognostic relevance of rectal magnetic resonance imaging findings before and after neoadjuvant chemoradiotherapy

This retrospective study was designed to compare prognostic relevance of magnetic resonance imaging (MRI) findings before and after neoadjuvant chemoradiotherapy (CRT). From 2002 to 2010, 399 patients who underwent surgery after CRT for rectal cancer (≥T3) and had adequate pre-CRT (mr) and post-CRT (ymr) MRI findings were examined. Factors examined included tumour (T), lymph node (N), mesorectal fascia (MRF), extramural venous invasion (EMVI), and tumour regression grade (TRG). Two Cox proportional hazard models were created using mr and ymr findings separately for overall survival (OS), disease-free survival (DFS), and local recurrence rate (LRR). Among mr findings, only mrEMVI was a significant prognostic factor for OS and DFS. Among ymr findings, ymrN, ymrMRF, and ymrEMVI were significant prognostic factors for OS and DFS, whereas ymrMRF and ymrEMVI were significant prognostic factors for LRR. C-indices tended to be higher for ymr findings than for mr findings (OS, 0.682 vs. 0.635; DFS, 0.660 vs. 0.631; LRR, 0.701 vs. 0.617). Survival outcomes of patients having all ymr risk factors were significantly poor (5-year OS, 52.4%; 5-year DFS, 38.1%; 5-year LRR, 27.7%). ymr findings showed better prognostic significance than mr findings. Among ymr findings, ymrN, ymrMRF, and ymrEMVI were independent prognostic factors for oncologic outcomes.

MRI-based radiomics signature for tumor grading of rectal carcinoma using random forest model

The present study aimed to construct prospective models for tumor grading of rectal carcinoma by using magnetic resonance (MR)-based radiomics features. A set of 118 patients with rectal carcinoma was analyzed. After imbalance-adjustments of the data using Synthetic Minority Oversampling Technique (SMOTE), the final data set was randomized into the training set and validation set at the ratio of 3:1. The radiomics features were captured from manually segmented lesion of magnetic resonance imaging (MRI). The most related radiomics features were selected using the random forest model by calculating the Gini importance of initial extracted characteristics. A random forest classifier model was constructed using the top important features. The classifier model performance was evaluated via receive operator characteristic curve and area under the curve (AUC). A total of 1,131 radiomics features were extracted from segmented lesion. The top 50 most important features were selected to construct a random forest classifier model. The AUC values of grade 1, 2, 3, and 4 for training set were 0.918, 0.822, 0.775, and 1.000, respectively, and the corresponding AUC values for testing set were 0.717, 0.683, 0.690, and 0.827 separately. The developed feature selection method and machine learning-based prediction models using radiomics features of MRI show a relatively acceptable performance in tumor grading of rectal carcinoma and could distinguish the tumor subjects from the healthy ones, which is important for the prognosis of cancer patients.

MRI of Rectal Cancer: Tumor Staging, Imaging Techniques, and Management

Rectal cancer is prone to local recurrence and systemic metastasis. However, owing to improvements in TNM staging and treatment, including a more widespread use of rectal MRI and increased radiologist awareness of the key rectal cancer TNM staging features, the mortality rate of rectal cancer has been declining over the past few decades in adults over 50 years of age. Currently, rectal MRI plays a key role in the pre- and posttreatment evaluation of rectal cancer, assisting the multidisciplinary team in tailoring the most appropriate treatment option. The benefits achieved with rectal MRI are strictly dependent on obtaining good-quality images, which is important for the characterization of the main anatomic structures and their relationship with the tumor. In primary staging, rectal MRI helps the radiologist (a) describe the tumor location and morphology, (b) provide its T and N categories, (c) detect the presence of extramural vascular invasion, and (d) identify its relationship with surrounding structures, including the sphincter complex and involvement of the mesorectal fascia. These features help diagnose locally advanced rectal tumors (categories T3c-d, T4, N1, and N2), for which neoadjuvant chemoradiotherapy (CRT) is indicated. In restaging after neoadjuvant CRT, in addition to reassessing the features noted during primary staging, rectal MRI can help in the assessment of treatment response, especially with the emergence of nonsurgical approaches such as "watch and wait." ^©RSNA, 2019.

Extramural venous invasion in rectal cancer: overview of imaging, histopathology, and clinical implications

OBJECTIVE

Extramural venous invasion (EMVI) is an independent prognostic factor for prediction of overall unfavorable outcomes in rectal cancer. While EMVI has traditionally been detected in postoperative pathologic specimens, MRI can provide this important piece of information preoperatively. This article reviews the methods of EMVI detection and their clinical implications for treatment and outcomes of rectal cancer.

CONCLUSION

EMVI has fundamental implications for rectal cancer prognosis and long-term outcomes. Since MRI has the advantage of preoperative detection of EMVI, it has been suggested that MRI-detected EMVI be incorporated for preoperative chemoradiotherapy (CRT) treatment stratification of rectal cancer for better patient triage and outcomes.

The clinical application value of MR diffusion-weighted imaging in the diagnosis of rectal cancer: A retrospective study

The present study evaluated the clinical potential of magnetic resonance (MR) diffusion-weighted imaging (DWI) in the diagnosis of rectal cancer.A total of 84 patients confirmed with rectal cancer were used as study subjects in the present study. All patients received conventional sequence MR T1WI, T2WI, and DWI examination as well as operative pathological examination. The differences between the MRI results and operative pathological results were analyzed.The diagnosis accordance rates of conventional sequence examination in stage T1, T2, T3, and T4 were 60.00%, 82.75%, 62.85%, and 80.00%, respectively. The diagnosis accordance rates of conventional sequence combined with DWI examination in stages T1, T2, T3, and T4 were 100.00%, 100.00%, 82.85%, and 100.00% respectively. The total diagnosis accordance rates in the T staging of rectal cancer with conventional (Routinely or generally applied) sequence examination and conventional sequence combined with DWI examination were 71.42% and 92.85%, respectively.The analysis on consistency of MR conventional sequence examination suggested that the conventional sequence combined with DWI examination is more consistent with pathological staging when compared with the convention sequence examination alone. MR DWI combined with conventional sequences reveals quite good accuracy in the T staging of rectal cancer.

Use of magnetic resonance imaging in rectal cancer patients: Society of Abdominal Radiology (SAR) rectal cancer disease-focused panel (DFP) recommendations 2017

PURPOSE

To propose guidelines based on an expert-panel-derived unified approach to the technical performance, interpretation, and reporting of MRI for baseline and post-treatment staging of rectal carcinoma.

METHODS

A consensus-based questionnaire adopted with permission and modified from the European Society of Gastrointestinal and Abdominal Radiologists was sent to a 17-member expert panel from the Rectal Cancer Disease-Focused Panel of the Society of Abdominal Radiology containing 268 question parts. Consensus on an answer was defined as ≥ 70% agreement. Answers not reaching consensus (< 70%) were noted.

RESULTS

Consensus was reached for 87% of items from which recommendations regarding patient preparation, technical performance, pulse sequence acquisition, and criteria for MRI assessment at initial staging and restaging exams and for MRI reporting were constructed.

CONCLUSION

These expert consensus recommendations can be used as guidelines for primary and post-treatment staging of rectal cancer using MRI.

Rectal MRI for Cancer Staging and Surveillance

MRI is an integral part of the multidisciplinary treatment of rectal adenocarcinoma. Staging MRI is performed to establish TNM stage and assess for prognostic factors, including circumferential resection margin status and presence of extramural vascular invasion. The results of staging MRI determine which patients will undergo preoperative neoadjuvant chemoradiation before resection. Restaging MRI is performed to evaluate for treatment response and may identify patients with no residual visible tumor who are candidates for a "watch and wait" strategy in lieu of resection. In addition, the results of MRI in conjunction with endoscopy determine the surgical technique used to remove the tumor.

Pelvic MRI: Is Endovaginal or Rectal Filling Needed?

Magnetic resonance imaging is the optimal modality for pelvic imaging. It is based on T2-weighted magnetic resonance (MR) sequences allowing uterine and vaginal cavity assessment as well as rectal evaluation. Anatomical depiction of these structures may benefit from distension, and conditions either developing inside the lumen of cavities or coming from the outside may then be better delineated and localized. The need for distension, either rectal or vaginal, and the way to conduct it are matters of debate, depending on indication for which the MR examination is being conducted. In this review, we discuss advantages and potential drawbacks of this technique, based on literature and our experience, in the evaluation of various gynecological and rectal diseases.

Rectal cancer MRI: protocols, signs and future perspectives radiologists should consider in everyday clinical practice

Abstract

Magnetic resonance imaging (MRI) allows to non-invasively evaluate rectal cancer staging and to assess the presence of “prognostic signs” such as the distance from the anorectal junction, the mesorectal fascia infiltration and the extramural vascular invasion. Moreover, MRI plays a crucial role in the assessment of treatment response after chemo-radiation therapy, especially considering the growing interest in the new conservative policy (wait and see, minimally invasive surgery). We present a practical overview regarding the state of the art of the MRI protocol, the main signs that radiologists should consider for their reports during their clinical activity and future perspectives.

Teaching Points

• MRI protocol for rectal cancer staging and re-staging.

• MRI findings that radiologists should consider for reports during everyday clinical activity.

• Perspectives regarding the development of latest technologies.

ACR Appropriateness Criteria® Pretreatment Staging of Colorectal Cancer

Colorectal cancers are common tumors in the United States and appropriate imaging is essential to direct appropriate care. Staging and treatment differs between tumors arising in the colon versus the rectum. Local staging for colon cancer is less integral to directing therapy given radical resection is often standard. Surgical options for rectal carcinoma are more varied and rely on accurate assessment of the sphincter, circumferential resection margins, and peritoneal reflection. These important anatomic landmarks are best appreciated on high-resolution imaging with transrectal ultrasound or MRI. When metastatic disease is suspected, imaging modalities that provide a global view of the body, such as CT with contrast or PET/CT may be indicated. Rectal cancer often metastasizes to the liver and so MRI of the liver with and without contrast provides accurate staging for liver metastases. This article focuses on local and distant staging and reviews the appropriateness of different imaging for both variants. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Imaging of colorectal cancer - the clue to individualized treatment

Colorectal cancer (CRC) is the most common gastrointestinal neoplasm and the second most common cause for cancer-related death in Europe. Imaging plays an important role both in the primary diagnosis, treatment evaluation, follow-up, and, to some extent, also in prevention. Like in the clinical setting, colon and rectal cancer have to be distinguished as two quite separate entities with different goals of imaging and, consequently, also different technical requirements. Over the past decade, there have been improvements in both more robust imaging techniques and new data and guidelines that help to use the optimal imaging modality for each scenario. For colon cancer, the continued research on computed tomography (CT) colonography (CTC) has led to high-level evidence that puts this technique on eye height to optical colonoscopy in terms of detection of cancer and polyps ≥10 mm. However, also for smaller polyps and thus for screening purposes, CTC seems to be an optimal tool. In rectal cancer, the technical requirements to perform state-of-the art imaging have recently been defined. Evaluation of T-stage, mesorectal fascia infiltration and extramural vascular invasion are the most important prognostic factors that can be identified on MRI. With this information, risk stratification both for local and distal failure is possible, enabling the clinician to tailor the optimal therapeutic approach in non-metastatic rectal cancer. Imaging of metastatic CRC is also covered, although the complex ramifications of treatment options in the metastatic setting are beyond the scope of this article. In this review, the most important recent developments in the imaging of colon and rectal cancer will be highlighted. If used in an interdisciplinary setting, this can lead to an individualized treatment concept for each patient.

Gadolinium-Based Contrast Agent During Pelvic MRI: Contribution to Patient Management in Rectal Cancer

BACKGROUND

Few publications exist regarding gadolinium-enhanced sequences in rectal MRI. None have evaluated its potential impact on patient management.

OBJECTIVE

This study aimed to assess whether gadolinium-enhanced sequences, including dynamic contrast enhancement, change radiologic interpretation and clinical management of rectal cancer.

DESIGN

This is a retrospective analysis of 100 rectal MRIs (50 baseline and 50 postneoadjuvant treatment), both without and with gadolinium-enhanced sequences. Treatment plans were rendered based on each radiologic interpretation for each case by a single experienced surgeon. Differences in radiologic interpretation and management were statistically analyzed.

SETTINGS

The study was conducted at the Memorial Sloan Kettering Cancer Center.

PATIENTS

Patients undergoing rectal MRI between 2011 and 2015 for baseline tumor staging and/or postneoadjuvant restaging were included.

MAIN OUTCOME MEASURES

Primary outcome measures were changes in radiologic tumor stage, tumor margins, and surgical planning with the use of gadolinium at baseline and postneoadjuvant time points.

RESULTS

At baseline, tumor downstaging occurred in 8 (16%) of 50 and upstaging in 4 (8%) of 50 with gadolinium. Postneoadjuvant treatment, upstaging occurred in 1 (2%) of 50 from T2 to T3a. At baseline, mean distances from tumor to anorectal ring, anal verge, and mesorectal fascia were not statistically different with gadolinium. However, in 7 patients, differences could have resulted in treatment changes, accounted for by changes in relationships to anterior peritoneal reflection (n = 4), anorectal ring (n = 2), or anal verge (n = 1). Postneoadjuvant treatment, distances to anorectal ring and anal verge (in centimeters) were statistically smaller with gadolinium (p = 0.0017 and p = 0.0151) but could not have resulted in clinically significant treatment changes.

LIMITATIONS

This study was limited by its retrospective design.

CONCLUSIONS

The use of gadolinium at baseline MRI could have altered treatment in 24% of patients because of differences in tumor stage or position. Postneoadjuvant treatment, gadolinium resulted in statistically smaller distances to sphincters, which could influence surgical decision for sphincter-preserving rectal resection. See Video Abstract at http://links.lww.com/DCR/A444.

Pitfalls in MRI of rectal cancer: What radiologists need to know and avoid

Preoperative staging of rectal cancer using magnetic resonance imaging (MRI) has become an important component of clinical management. Although MRI is the modality of choice for rectal cancer diagnosis and staging, there are certain inherent potential pitfalls that radiologists need to recognize in order to avoid imaging misinterpretation, including choice of MRI protocol; choice of MRI technique; potential mimickers of rectal cancer; mucinous rectal tumor; differentiation between extramural tumor invasion and desmoplastic reaction; differentiation between low rectal cancer and anal cancer; problems relating to nodal involvement, peritoneal reflection, and mesorectal fascia invasion; and, challenges associated with restaging, post-treatment changes, and complications. The aim of this article was to heighten radiologist awareness of these potential pitfalls in order to improve diagnosis, decision-making, and patient outcomes.

Rectal cancer confined to the bowel wall: the role of 3 Tesla phased-array MR imaging in T categorization

OBJECTIVE

To determine the diagnostic value of 3 Tesla MR imaging in detection of mucosal (Tis), submucosal (T₁) and muscularis propria (T₂) invasion in patients with early rectal cancer.

METHODS

A total of 50 consecutive patients who underwent 3 Tesla MR imaging and curative-intent intervention for MRI-staged Tis/T₁/T₂ rectal cancer from March 2012 to December 2016 were included. The radiological T category of each rectal tumour was compared retrospectively with histopathological results assessed according to the tumor, node, metastasis (TNM) classification. The sensitivities, specificities, and overall accuracy rates of 3 Tesla MR imaging for Tis, T₁, and T₂ cases were calculated using MedCalc statistical software v. 16.

RESULTS

The sensitivity, specificity, PPV, NPV of 3 Tesla MR imaging in T categorization for T₂ were: 93.7% [95% CI (0.79-0.99)], 77.7% [95% CI (0.52-0.93)], 88.2% [95% CI (0.75-0.94)] and 87.5% [95% CI (0.64-0.96)]; for T₁ were 92% [95% CI (0.63-0.99)], 91.8% [95% CI (0.78-0.98)], 80% [95% CI (0.57-0.92)] and 97.1% [95% CI (0.83-0.99)]; for Tis were: 20% [95% CI (0.51-0.71)], 100% [95% CI (0.92-1)], 100%, 91.8% [95% CI (0.87-0.94)], respectively. MR categorization accuracy rates for T₂, T₁ and Tis were calculated as 88, 92 and 92%, respectively.

CONCLUSION

3 Tesla MR imaging seems to be useful for accurate categorization of T-stage in early rectal cancer, especially for T₁ cancers. The method is not a reliable tool to detect Tis cases. The potential for overstaging and understaging of the technique should be realized and taken into consideration when tailoring the treatment protocol for each patient. Advances in knowledge: High-resolution MR with phased-array coil is being increasingly used in the pre-operative assessment of rectal cancer. 3 Tesla high-resolution MR imaging allows improved definition of bowel wall and tumour infiltration.

Haralick's texture features for the prediction of response to therapy in colorectal cancer: a preliminary study

PURPOSE

Haralick features Texture analysis is a recent oncologic imaging biomarker used to assess quantitatively the heterogeneity within a tumor. The aim of this study is to evaluate which Haralick's features are the most feasible in predicting tumor response to neoadjuvant chemoradiotherapy (CRT) in colorectal cancer.

MATERIALS AND METHODS

After MRI and histological assessment, eight patients were enrolled and divided into two groups based on response to neoadjuvant CRT in complete responders (CR) and non-responders (NR). Oblique Axial T2-weighted MRI sequences before CRT were analyzed by two radiologists in consensus drawing a ROI around the tumor. 14 over 192 Haralick's features were extrapolated from normalized gray-level co-occurrence matrix in four different directions. A dedicated statistical analysis was performed to evaluate distribution of the extracted Haralick's features computing mean and standard deviation.

RESULTS

Pretreatment MRI examination showed significant value (p < 0.05) of 5 over 14 computed Haralick texture. In particular, the significant features are the following: concerning energy, contrast, correlation, entropy and inverse difference moment.

CONCLUSIONS

Five Haralick's features showed significant relevance in the prediction of response to therapy in colorectal cancer and might be used as additional imaging biomarker in the oncologic management of colorectal patients.

MRI Evaluation of Rectal Cancer: Staging and Restaging

Magnetic resonance imaging (MRI) plays an important role in the staging and restaging of rectal cancer. Multiplanar high-resolution (≤3-mm section thickness) T2-weighted images are the primary sequences used for rectal cancer staging. No preprocedural bowel cleansing regimen, intravenous contrast material, nor endorectal coil is necessary. MRI is highly accurate for differentiating T1-T2 disease from T3 and T4 disease, an important distinction as patients with T3 and T4 tumors typically undergo preoperative neoadjuvant chemoradiation before resection. At MRI, the muscularis propria appears as a thin black line encircling the outer wall of the rectum, and tumor extension through this line indicates T3 disease. Further tumor extension into adjacent organs indicates T4 disease. Endorectal ultrasound is generally preferred to differentiate T1 (submucosal involvement) from T2 (extension into but no disruption of muscularis propria) disease. MRI is also accurate in the assessment of tumor involvement of the mesorectal fascia. Tumor involvement of the mesorectal fascia increases the likelihood of recurrence following resection. MRI is less accurate for determination of lymph node status, though heterogeneous signal intensity and irregular margins are suggestive of node positive disease. Approximately 10%-30% of patients who undergo preoperative chemoradiation experience a complete pathologic response that is defined as no residual tumor found at histopathologic analysis of the resected specimen. The addition of diffusion-weighted images to T2-weighted images improves the accuracy of restaging examinations for determination of complete pathologic responders.

Initial Staging of Locally Advanced Rectal Cancer and Regional Lymph Nodes: Comparison of Diffusion-Weighted MRI With 18F-FDG-PET/CT

Purpose

The aim of the study was to compare diffusion-weighted MRI (DW-MRI) parameters with ¹⁸F-FDG PET/CT in primary locally advanced rectal cancer (LARC).

Methods

From October 2012 to September 2014, 24 patients with histologically confirmed and untreated LARC (T3–T4) prospectively underwent a pelvic 1.5-T DW-MRI (b = 0 s/mm², b = 600 s/mm²) and a whole-body ¹⁸F-FDG PET/CT, before neoadjuvant therapy. The 2 examinations were performed on the same day. Two readers measured ¹⁸F-FDG SUVmax and SUVmean of the rectal tumor and of the pathological regional lymph nodes on PET/CT and compared these with minimum and mean values of the ADC (ADCmin and ADCmean) on maps generated from DW-MRI. The diagnostic performance of ADC values in identifying pathological lymph nodes was also assessed.

Results

Regarding tumors (n = 24), we found a significant negative correlation between SUVmean and corresponding ADCmean values (ρ = −0.61, P = 0.0017) and between ADCmin and SUVmax (ρ = −0.66, P = 0.0005). Regarding the lymph nodes (n = 63), there was a significant negative correlation between ADCmean and SUVmean values (ρ = −0.38, P = 0.0021), but not between ADCmin and SUVmax values (ρ = −0.11, P = 0.41). Neither ADCmean nor ADCmin values helped distinguish pathological from benign lymph nodes (AUC of 0.24 [confidence interval, 0.10–0.38] and 0.41 [confidence interval, 0.22–0.60], respectively).

Conclusions

The correlations between ADCmean and SUVmean suggest an association between tumor cellularity and metabolic activity in untreated LARC and in regional lymph nodes. However, compared with ¹⁸F-FDG PET/CT, ADC values are not reliable for identifying pathological lymph nodes.

Diagnostic Accuracy of MRI for Assessment of T Category and Circumferential Resection Margin Involvement in Patients With Rectal Cancer: A Meta-Analysis

BACKGROUND

The prognosis of rectal cancer is directly related to the stage of the tumor at diagnosis. Accurate preoperative staging is essential for selecting patients to receive optimal treatment.

OBJECTIVE

The purpose of this study was to evaluate the diagnostic performance of MRI in tumor staging and circumferential resection margin involvement in rectal cancer.

DATA SOURCES

A systematic literature search was performed in MEDLINE, EMBASE, PubMed, Cochrane Database of Systematic Reviews, and Web of Science database.

STUDY SELECTION

Original articles from 2000 to 2016 on the diagnostic performance of MRI in the staging of rectal cancer and/or assessment of mesorectal fascia status were eligible.

MAIN OUTCOME MEASURES

Pooled diagnostic statistics including sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio were calculated for invasion of muscularis propria, perirectal tissue, and adjacent organs and for circumferential resection margin involvement through bivariate random-effects modeling. Summary receiver operating characteristic curves were fitted, and areas under summary receiver operating characteristic curves were counted to evaluate the diagnostic performance of MRI for each outcome.

RESULTS

Thirty-five studies were eligible for this meta-analysis. Preoperative MRI revealed the highest sensitivity of 0.97 (95% CI, 0.96-0.98) and specificity of 0.97 (95% CI, 0.96-0.98) for muscularis propria invasion and adjacent organ invasion. Areas under summary receiver operating characteristic curves indicated good diagnostic accuracy for each outcome, with the highest of 0.9515 for the assessment of adjacent organ invasion. Significant heterogeneity existed among studies. There was no notable publication bias for each outcome.

LIMITATIONS

This meta-analysis revealed relatively high diagnostic accuracy for preoperative MRI, although significant heterogeneity existed. Therefore, exploration should be focused on standardized interpretation criteria and optimal MRI protocols for future studies.

CONCLUSIONS

MRI showed relatively high diagnostic accuracy for preoperative T staging and circumferential resection margin assessment and should be reliable for clinical decision making.

Magnetic resonance imaging of rectal cancer: staging and restaging evaluation

Magnetic resonance imaging is used to non-invasively stage and restage rectal adenocarcinomas. Accurate staging is important as the depth of tumor extension and the presence or absence of lymph node metastases determines if an individual will undergo preoperative neoadjuvant chemoradiation. Accurate description of tumor location is important for presurgical planning. The relationship of the tumor to the anal sphincter in addition to the depth of local invasion determines the surgical approach used for resection. High-resolution T2-weighted imaging is the primary sequence used for initial staging. The addition of diffusion-weighted imaging improves accuracy in the assessment of treatment response on restaging scans. Approximately 10%-30% of individuals will experience a complete pathologic response following chemoradiation with no residual viable tumor found in the resected specimen at histopathologic assessment. In some centers, individuals with no residual tumor visible on restaging MR who are thought to be at high operative risk are monitored with serial imaging and a "watch and wait" approach in lieu of resection. Normal rectal anatomy, MR technique utilized for staging and restaging scans, and TMN staging are reviewed. An overview of surgical techniques used for resection including newer, minimally invasive endoluminal techniques is included.

MRI of Rectal Cancer: An Overview and Update on Recent Advances

OBJECTIVE

MRI is the modality of choice for rectal cancer staging. The high soft-tissue contrast of MRI accurately assesses the extramural tumor spread and relation to mesorectal fascia and the sphincter complex. This article reviews the role of MRI in the staging and treatment of rectal cancer. The relevant anatomy, MRI techniques, preoperative staging, post-chemoradiation therapy (CRT) imaging, and tumor recurrence are discussed with special attention to recent advances in knowledge.

CONCLUSION

MRI is the modality of choice for staging rectal cancer to assist surgeons in obtaining negative surgical margins. MRI facilitates the accurate assessment of mesorectal fascia and the sphincter complex for surgical planning. Multiparametric MRI may also help in the prediction and estimation of response to treatment and in the detection of recurrent disease.

MRI tumor volume reduction rate vs tumor regression grade in the pre-operative re-staging of locally advanced rectal cancer after chemo-radiotherapy

OBJECTIVE

To compare tumor volume reduction rate (TVRR) measured by MR volumetry after preoperative chemoradiotherapy (CRT) and pathological tumor regression grade (TRG) in locally advanced rectal cancer (LARC).

MATERIAL AND METHODS

In total, 20 patients with LARC (cT3-T4) treated with CRT followed by Total Mesorectal Excision (TME) between April 2011 and April 2013 were analyzed retrospectively. Pre- and post- CRT tumor volumes (MR volumetry) were measured on 3D MR sequences. TVRR was determined using the equation TVRR (%)=(pre-CRT tumor volume-post-CRT tumor volume)×100/pre-CRT tumor volume. The downstaging (defined as ypT0-T2) of tumor mass was evaluated and the correlation between TVRR and TRG was calculated with the method proposed by Dworak using the Spearman rank test.

RESULTS

The median TVRR was 77.3% (range, 26.4-99.3%); TVRR was >60% in 18 cases (90%) and in 8 of these patients (44.4 %) it was >80%. Downstaging of tumor lesions was obtained in 15 patients (75%). In 4 cases there was a complete tumor regression (TRG4) at histological examination and in the same patients there was also a TVRR>80% measured by MR volumetry. A statistically significant correlation between TVRR and TRG (r(s)=0.5466, p=0.0126) was observed.

CONCLUSION

TVRR after preoperative CRT correlates with TRG in LARC. The MR volumetry is a prognostic factor to estimate the tumor response after preoperative CRT. TVRR data may be an useful biomarker for tailoring surgery and postoperative adjuvant chemotherapy.

Current imaging of rectal cancer

Recent advances in rectal cancer surgery and treatment as well as new developments in magnetic resonance imaging (MRI) technique have led to extensive research in the field of preoperative imaging of rectal cancer and to an abundant literature. Pelvic MRI has indeed become an important part of the decision-making process for patients with rectal cancer. The aim of this article is to give current guidelines in terms of which imaging method to perform and also to review the role of imaging, with emphasis on MRI, not only for tumor primary staging but also for reevaluation of the tumor after neoadjuvant therapy, highlighting the role of new so-called "functional MR techniques". Future trends are also discussed.

Endorectal ultrasonography, strain elastography and MRI differentiation of rectal adenomas and adenocarcinomas

AIM

Strain elastography is a method for recording tissue hardness. Strain in different areas may be compared using strain ratio (SR). The aims of this study were to validate a previously proposed SR cut-off value of 1.25 for differentiating adenocarcinomas from adenomas and to compare the performance of endorectal ultrasonography (ERUS), strain elastography and MRI in the same patients.

METHOD

A prospective evaluation of 120 consecutive patients with rectal neoplasia, using a predetermined elastography strain ratio cut-off value, was performed to differentiate adenomas from adenocarcinomas. ERUS and MRI were performed according to standard routine at Haukeland University Hospital, defining T0 as adenomas and T1-T4 as adenocarcinomas. Subsequent histopathology was used as the reference standard.

RESULTS

Histopathological evaluation revealed 21 adenomas and 99 adenocarcinomas. Sensitivity, specificity and accuracy (with 95% CI) were as follows: ERUS: 0.96 (0.90-0.99), 0.62 (0.40-0.80) and 0.90 (0.83-0.94); elastography SR: 0.96 (0.90-0.99), 0.86 (0.66-0.96) and 0.94 (0.88-0.97); and MRI: 0.99 (0.94-1.00), 0.07 (0.00-0.31) and 0.87 (0.80-0.93).

CONCLUSION

This study confirms that the elastography SR assessment accurately differentiates sessile adenomas from adenocarcinomas. SR assessment has a superior ability to differentiate adenomas and adenocarcinomas when compared with ERUS and MRI. MRI examination seems unable to recognize adenomas and should be interpreted with care when early-stage rectal neoplasia is suspected.

Factors affecting the restaging accuracy of magnetic resonance imaging after preoperative chemoradiation in patients with rectal cancer

PURPOSES

We evaluated patient or tumor factors associated with the preoperative restaging accuracy of magnetic resonance imaging (MRI) for determining T and N stages as well as circumferential resection margin (CRM) involvement after chemoradiation (CRT) in patients with locally advanced rectal cancer.

METHODS

Seventy-seven patients with rectal cancer that were treated with preoperative CRT (50.4 Gy) followed by radical resection were included. Post-CRT MRI was performed approximately 4 weeks after preoperative CRT.

RESULTS

The median tumor distance from the anal verge was 6 cm, 48 (62%) of which were anterior and 29 (38%) posterior. The median tumor diameter was 3 cm. A stage-by-stage comparison showed that correct staging occurred in 62%, 43%, and 86% of patients for T staging, N staging, and CRM prediction, respectively. Shorter distance to the anal verge (<5 cm), smaller tumor diameter (<1 cm), and anterior tumor location were associated with incorrect T staging. There were no significant variables in terms of N staging accuracy. Shorter tumor distance and anterior tumor location were associated with incorrect CRM prediction.

CONCLUSIONS

Our findings suggest that specific tumor factors such as small, distal, or anterior rectal tumors are closely associated with the accuracy of MRI after preoperative CRT.