Effect of gadolinium contrast-enhanced T1-weighted magnetic resonance imaging for detecting extramural venous invasion in rectal cancer

Prediction of T Stage of Rectal Cancer After Neoadjuvant Therapy by Multi-Parameter Magnetic Resonance Radiomics Based on Machine Learning Algorithms

INTRODUCTION

Since the response of patients with rectal cancer (RC) to neoadjuvant therapy is highly variable, there is an urgent need to develop accurate methods to predict the post-treatment T (pT) stage. The purpose of this study was to evaluate the utility of multi-parametric MRI radiomics models and identify the most accurate machine learning (ML) algorithms for predicting pT stage of RC.

METHOD

This retrospective study analyzed pretreatment clinical features of 171 RC patients who underwent 3 T MRI prior to neoadjuvant therapy and subsequent total mesorectal excision. Tumors were manually drawn as regions of interest (ROI) layer by layer on high-resolution T2-weighted image (T2WI) and contrast-enhanced T1-weighted image (CE-T1WI) using ITK-SNAP software. The most relevant features of pT stage from CE-T1WI, T2WI, and fusion features (combination of clinical features, CE-T1WI, and T2WI radiomics features) were extracted by the Least Absolute Shrinkage and Selection Operator method. Clinical, CE-T1WI radiomics, T2WI radiomics, and fusion models were established by ML multiple classifiers.

RESULTS

In the clinical model, the LightGBM algorithm demonstrated the highest efficiency, with AUC values of 0.857 and 0.702 for the training and test cohorts, respectively. For the T2WI and CE-T1WI models, the SVM algorithm was the most efficient; AUC = 0.969 and 0.868 in the training cohort, and 0.839 and 0.760 in the test cohort, respectively. The fusion model yielded the highest predictive performance using the LR algorithm; AUC = 0.967 and 0.932 in the training and test cohorts, respectively.

CONCLUSION

Radiomics features extracted from CE-T1WI and T2WI images and clinical features were effective predictors of pT stage in patients with rectal cancer who underwent neoadjuvant therapy. ML-based multi-parameter MRI radiomics model incorporating relevant clinical features can improve the pT stage prediction accuracy of RC.

An MRI-based scoring system for pretreatment risk stratification in locally advanced rectal cancer

BACKGROUND

Accurately assessing the risk of recurrence in patients with locally advanced rectal cancer (LARC) before treatment is important for the development of treatment strategies. The purpose of this study is to develop an MRI-based scoring system to predict the risk of recurrence in patients with LARC.

METHODS

This was a multicenter observational study that enrolled participants who underwent neoadjuvant chemoradiotherapy. To evaluate the risk of recurrence in these patients, we developed the mrDEC scoring system and assessed inter-reader agreement. Additionally, we plotted Kaplan-Meier curves to compare the 3-year disease-free survival (DFS) and 5-year overall survival (OS) rates among patients with different mrDEC scores.

RESULTS

A total of 1287 patients with LARC were included in this study. We observed substantial inter-reader agreement for mrDEC. Based on the mrDEC scores ranging from 0 to 3, the patients were categorized into four groups. The 3-year DFS rates for the groups were 91.0%, 79.5%, 65.5%, and 44.0% (P < 0.0001), respectively, and the 5-year OS rates were 92.9%, 87.1%, 74.8%, and 44.5%, respectively (P < 0.0001).

CONCLUSIONS

The mrDEC scoring system proved to be an effective tool for predicting the prognosis of patients with LARC and can assist clinicians in clinical decision-making.

Predictive value of lesion morphology in rectal cancer based on MRI before surgery

OBJECTIVE

To explore the relationship of MRI morphology of primary rectal cancer with extramural vascular invasion (EMVI), metastasis and local recurrence.

MATERIALS AND METHODS

This retrospective study included 153 patients with rectal cancer. Imaging factors and histopathological index including nodular projection (NP), cord sign (CS) at primary tumor margin, irregular nodules (IN) of mesorectum, MRI-detected peritoneal reflection invasion (PRI), range of rectal wall invasion (RRWI), patterns and length of tumor growth, maximal extramural depth (EMD), histologically confirmed local node involvement (hLN), MRI T stage, MRI N stage, MRI-detected extramural vascular invasion (mEMVI) and histologically confirmed extramural vascular invasion (hEMVI) were evaluated. Determining the relationship between imaging factors and hEMVI, synchronous metastasis and local recurrence by univariate analysis and multivariable logistic regression, and a nomogram validated internally via Bootstrap self-sampling was constructed based on the latter.

RESULTS

Thirty-eight cases of hEMVI, fourteen cases of synchronous metastasis and ten cases of local recurrence were observed among 52 NP cases. There were 50 cases of mEMVI with moderate consistency with hEMVI (Kappa = 0.614). NP, CS, EMD and mEMVI showed statistically significant differences in the negative and positive groups of hEMVI, synchronous metastasis, and local recurrence. Compared to patients with local mass growth, the rectal tumor with circular infiltration had been found to be at higher risk of synchronous metastasis and local recurrence (P < 0.05). NP and IN remained as significant predictors for hEMVI, and mEMVI was a predictor for synchronous metastasis, while PRI and mEMVI were predictors for local recurrences. The nomogram for predicting hEMVI demonstrated a C-index of 0.868, sensitivity of 86.0%, specificity of 79.6%, and accuracy of 81.7%.

CONCLUSION

NP, CS, IN, large EMD, mEMVI, and circular infiltration are significantly associated with several adverse prognostic indicators. The nomogram based on NP has good predictive performance for preoperative EMVI. mEMVI is a risk factor for synchronous metastasis. PRI and mEMVI are risk factors for local recurrence.

MRI restaging of rectal cancer: The RAC (Response-Anal canal-CRM) analysis joint consensus guidelines of the GRERCAR and GRECCAR groups

PURPOSE

To develop guidelines by international experts to standardize data acquisition, image interpretation, and reporting in rectal cancer restaging with magnetic resonance imaging (MRI).

MATERIALS AND METHODS

Evidence-based data and experts' opinions were combined using the RAND-UCLA Appropriateness Method to attain consensus guidelines. Experts provided recommendations for reporting template and protocol for data acquisition were collected; responses were analysed and classified as "RECOMMENDED" versus "NOT RECOMMENDED" (if ≥ 80% consensus among experts) or uncertain (if < 80% consensus among experts).

RESULTS

Consensus regarding patient preparation, MRI sequences, staging and reporting was attained using the RAND-UCLA Appropriateness Method. A consensus was reached for each reporting template item among the experts. Tailored MRI protocol and standardized report were proposed.

CONCLUSION

These consensus recommendations should be used as a guide for rectal cancer restaging with MRI.

Synthetic phase-sensitive inversion-recovery vessel for assessing extramural venous invasion in patients with rectal cancer: imaging quality and added value to T2-wighted imaging

OBJECTIVES

To evaluate the imaging quality of a synthetic phase-sensitive inversion recovery (SyPSIR) vessel and to add value to T2-weighted imaging (T2WI) for extramural venous invasion (EMVI) detection in patients with rectal cancer.

METHODS

Participants in this retrospective study underwent preoperative synthetic MRI between October 2020 and April 2022. SyPSIR image reconstruction was performed with a single inversion time of 10 ms. A junior and a senior radiologist evaluated the imaging quality, including overall imaging quality scores, motion artifact scores, and relative image signal intensity contrast between the tumor and peritumoral vessels (SI_tumor-vessel), of both T2WI and SyPSIR vessels. Differences in imaging quality between the two methods were assessed using the Wilcoxon signed-rank test and two-sample t-test. EMVI scores were recorded for T2WI and T2WI+SyPSIR vessel. The area under the receiver operating characteristic curve (AUC) was calculated to evaluate the diagnostic performance.

RESULTS

A total of 106 patients (35 EMVI+ and 71 EMVI-) were evaluated. There were no statistically significant differences in the overall image quality scores, motion artifacts, or SI_tumor-vessel (p = 0.08-0.93) between the T2WI and SyPSIR vessels. On combining T2WI and SyPSIR vessels, the AUC for pathological EMVI+ diagnoses increased from 0.65 to 0.88 for the junior radiologist and from 0.86 to 0.96 for the senior radiologist. Furthermore, the sensitivity of the analyses by junior and senior radiologists increased from 0.40 to 0.77 and 0.49 to 0.86, respectively.

CONCLUSION

A SyPSIR vessel can provide additional information to improve the diagnostic efficiency of pathological EMVI in rectal cancer, which may be beneficial for individualized clinical treatment.

KEY POINTS

• SyPSIR vessel and T2WI had similar imaging quality. • EMVI evaluation in SyPSIR vessel has a high inter-observer agreement. • The SyPSIR vessel has the potential to improve the diagnostic efficiency of EMVI detection in rectal cancer.

MRI Evaluation of Extramural Venous Invasion (EMVI) with Rectal Carcinoma Using High Resolution T2 and Combination of High Resolution T2 and Contrast Enhanced T1 Weighted Imaging

Background:

EMVI is a direct invasion of a vein by a tumor. As a predictor of hematogenous metastasis, it is a poor prognostic factor in rectal cancer and can be accurately identified on MRI prior to surgical procedure.

Objective:

To evaluate the role of contrast-enhanced T1-weighted magnetic resonance imaging (CET1WI) in addition to high-resolution T2-weighted imaging (HRT2WI) in assessing extramural venous invasion (EMVI) of rectal cancer.

Methods:

In all 195 patients with rectal cancer, HRT2WI and CET1WI sequences were produced within pre-operative MRI for the purpose of assessing for the presence of EMVI (mrEMVI). CET1WI sequences were produced following administration of Gadolinium contrast medium. mrEMVI assessment results were classified into two groups. Group A consisted of mrEMVI assessment results obtained using HRT2WI sequences only. Group B consisted of mrEMVI assessment results obtained using a combination of HRT2WI + CET1WI sequences. Results obtained for each group (A and B) were correlated with a histopathological finding (pEMVI) as a reference standard.

Results:

Out of a total of 195 rectal cancer patients, mrEMVI was positive in 41 (21%) patients in group A, and in 45 (23%) patients in group B. Histopathological finding demonstrated pEMVI in 54 (27.7%) patients. A statistical analysis of group A (HRT2WI sequences) resulted in 75.9% sensitivity to mrEMVI and 96.4% specificity, Positive Predictive Value of 89.1% and Negative Predictive Value of 91.2% (95% confidence interval (CI), p< 0.05). Statistical analysis of group B (HRT2WI + CET1WI sequences) resulted in 83.3% sensitivity to mrEMVI and 98.5% specificity, Positive Predictive Value of 89.1% and Negative Predictive Value of 91.2% (CI 95%, p< 0.05).

Conclusion:

T1-weighted magnetic resonance imaging (CET1WI) in addition to high-resolution T2-weighted imaging (HRT2WI) increased evaluation of extramural venous invasion (EMVI) of rectal cancer.

MRI-detected extramural venous invasion of rectal cancer: Multimodality performance and implications at baseline imaging and after neoadjuvant therapy

MRI is routinely used for rectal cancer staging to evaluate tumor extent and to inform decision-making regarding surgical planning and the need for neoadjuvant and adjuvant therapy. Extramural venous invasion (EMVI), which is intravenous tumor extension beyond the rectal wall on histopathology, is a predictor for worse prognosis. T2-weighted images (T2WI) demonstrate EMVI as a nodular-, bead-, or worm-shaped structure of intermediate T2 signal with irregular margins that arises from the primary tumor. Correlative diffusion-weighted images demonstrate intermediate to high signal corresponding to EMVI, and contrast enhanced T1-weighted images demonstrate tumor signal intensity in or around vessels. Diffusion-weighted and post contrast images may increase diagnostic performance but decrease inter-observer agreement. CT may also demonstrate obvious EMVI and is potentially useful in patients with a contraindication for MRI. This article aims to review the spectrum of imaging findings of EMVI of rectal cancer on MRI and CT, to summarize the diagnostic accuracy and inter-observer agreement of imaging modalities for its presence, to review other rectal neoplasms that may cause EMVI, and to discuss the clinical significance and role of MRI-detected EMVI in staging and restaging clinical scenarios.

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.

Risk of nodal disease in patients with MRI-detected extramural vascular invasion in rectal cancer: a systematic review and meta-analysis

BACKGROUND

The impact of magnetic resonance imaging-detected extramural vascular invasion (mrEMVI) in distant metastasis is well known but its correlation with prevalence of lymph node metastasis is less studied. The aim of this systematic review and meta-analysis was to assess the prevalence of nodal disease in mrEMVI-positive and negative cases in rectal cancer.

METHODS

Following guidelines of Preferred Reporting Items for Systematic Reviews and Meta-Analyses, a systematic literature search in PubMed, Web of Science, Cochrane Library, and EMBase was carried out to identify relevant studies published up to May 2019.

RESULTS

Our literature search generated 10 studies (863 and 1212 mrEMVI-positive and negative patients, respectively). The two groups (mrEMVI-positive and negative) were significantly different in terms of nodal disease status (odds ratio [OR] 3.15; 95% confidence interval [CI] 2.12-4.67; p < 0.001). The prevalence of nodal disease was 75.90% vs 52.56% in the positive mrEMVI vs negative mrEMVI group, respectively (p < 0.001). The prevalence of positive lymph node in positive mrEMVI patients treated with neoadjuvant/adjuvant chemoradiotherapy (nCRT/CRT) (OR 2.47; 95% CI 1.65-3.69; p < 0.001) was less compared with the patients who underwent surgery alone (OR 6.25; 95% CI 3.74-10.44; p < 0.001).

CONCLUSION

The probability of positive lymph nodes in cases of positive mrEMVI is distinctly greater compared with negative cases in rectal cancer. Positive mrEMVI indicates risk of nodal disease prevalence increased by threefold in rectal cancer.

Primary and post-chemoradiotherapy MRI detection of extramural venous invasion in rectal cancer: the role of diffusion-weighted imaging

OBJECTIVE

To assess the added value of diffusion-weighted imaging (DWI) to high-resolution T2-weighted sequences (HRT2w) in MRI detection of extramural venous infiltration (EMVI), according to the previous experience of radiologists.

METHODS

A cross-sectional study of a retrospective database including 1.5 T MRI records from 100 patients with biopsy-proven rectal cancer (2011-2016; 75 male/25 female, average 63 y/o), which included primary staging (54) and post-chemoradiotherapy follow-up MRIs (46). The reference standard was histology of surgical specimens. All cases were individually blindly reviewed by ten radiologists: three specialists in abdominal radiology, three specialized in different areas and four residents. In each case, the presence of EMVI was assessed twice: first, using just HRT2w; second, with DWI added to HRT2w. The results were pooled by experience, analyzing sensitivity, specificity, accuracy (area under ROC curve), likelihood ratios, predictive values and overstaging/understaging.

RESULTS

Addition of DWI improved diagnostic performance by specialists radiologists, particularly post-chemoradiotherapy (accuracy 0.74-0.84; positive likelihood ratio 3.9-9.1; overstaging 16-8%), less so at primary staging (specificity 76-87.2%; overstaging 21-11%). Non-specialist radiologists also improved, but only at primary staging (accuracy 0.59-0.63). Residents showed small changes, except for notably increased sensitivity in both primary staging (35.7-43%) and post-chemoradiotherapy (41.7-58.3%) staging, at the expense of increased overstaging.

CONCLUSIONS

The addition of DWI improved the diagnostic performance of EMVI by experienced radiologists, downgrading overstaging, especially in post-chemoradiotherapy follow-up. It resulted in fewer changes for inexperienced radiologists (enhanced primary staging) and residents (increased sensitivity).

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.

Clinical value of MRI-detected extramural venous invasion in rectal cancer

Extramural venous invasion (EMVI) is associated with a poor prognosis and a poor overall survival rate in rectal cancer. It can independently predict local and distant tumor recurrences. Preoperative EMVI detection in rectal cancer is useful for determining the treatment strategy. EMVI status is beneficial for the post-treatment evaluation and analysis of rectal cancer. Magnetic resonance imaging (MRI) is a non-invasive diagnostic modality with no radiation effects. High-resolution MRI can detect EMVI with high accuracy. In addition, MRI results are equal to or even better than pathological results in the detection of medium to large EMVI in rectal cancer. MRI-detected EMVI (mrEMVI) can be used as a potential biomarker that facilitates treatment methods. This review highlights the importance of MRI before and after rectal cancer treatment. In addition, we analyze the prognostic correlation between mrEMVI and circulating tumor cells (CTC) in rectal cancer. This article may help shed light on the significance of mrEMVI.