Post-treatment fistulas in patients with rectal cancer: MRI with rectal superparamagnetic contrast agent

Diagnostic accuracy of endoscopic ultrasound, computed tomography, magnetic resonance imaging, and endorectal ultrasonography for detecting lymph node involvement in patients with rectal cancer: A protocol for an overview of systematic reviews

BACKGROUND

Rectal cancer is one of the most common tumors and is the leading cause of cancer-related deaths in developed countries. Lymph node involvement remains the strongest prognostic factor associated with a worse prognosis in patients with rectal cancer. Several systematic reviews have investigated the accuracy of endoscopic ultrasound, computed tomography, magnetic resonance imaging, and endorectal ultrasonography for lymph node involvement of rectal cancer and compared the diagnostic accuracy of different imaging techniques, but there are considerable differences in conclusions. This study aims to assess the methodological quality and reporting quality of systematic reviews and to determine which diagnostic imaging techniques is the optimal modality for the diagnosis of lymph node involvement in patients with rectal cancer.

METHODS

We will search PubMed, EMBASE, Cochrane Library, and Chinese Biomedicine Literature to identify relevant studies from inception to June 2018. We will include systematic reviews that evaluated the accuracy of diagnostic imaging techniques for lymph node involvement. The methodological quality will be assessed using AMASAR checklist, and the reporting quality will be assessed using PRISMA-DTA checklist. The pairwise meta-analysis and indirect comparisons will be performed using STATA V.12.0.

RESULTS

The results of this overview will be submitted to a peer-reviewed journal for publication.

CONCLUSION

This overview will provide comprehensive evidence of different diagnostic imaging techniques for detecting lymph node involvement in patients with rectal cancer.

ETHICS AND DISSEMINATION

Ethics approval and patient consent are not required as this study is an overview based on published systematic reviews.

PROSPERO REGISTRATION NUMBER

CRD42018104906.

DCE-MRI time-intensity curve visual inspection to assess pathological response after neoadjuvant therapy in locally advanced rectal cancer

PURPOSE

To investigate the potential of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) to discriminate responder from non-responder patients after preoperative chemoradiotherapy (pCRT) in locally advanced rectal cancer (LARC).

MATERIALS AND METHODS

One hundred and fifty-eight consecutive patients were enrolled in this prospective study. We compared morphological MRI (mMRI) using T2-weighted images about tumor presence and invasiveness, and functional DCE-MRI using time-intensity curve (TIC) visual inspection (qMRI), classifying TIC shape into three types: type 1, persistent enhancement; type 2, high enhancement with plateau; type 3, high enhancement with wash-out. Clinical TNM was obtained before and after CRT by radiological consensus of two expert radiologists. Pathological tumor-nodes-metastasis classification and tumor regression grade (TRG) were confirmed as the golden standard. Non-parametric test, sensitivity, specificity, and positive and negative predictive values were calculated.

RESULTS

Ninety-eight patients (62%) were classified as responders (TRG ≤ 2), while 60 (38%) were classified as non-responders. Sensitivity, specificity, and accuracy were 52, 78, and 62% for mMRI, and 81, 85, and 82% for qMRI, respectively.

CONCLUSIONS

TIC visual inspection may be one of the potential biomarkers over morphological analysis using DCE-MRI data to assess pathological response after pCRT in LARC.

Standardized Index of Shape (DCE-MRI) and Standardized Uptake Value (PET/CT): Two quantitative approaches to discriminate chemo-radiotherapy locally advanced rectal cancer responders under a functional profile

Purpose

To investigate dynamic contrast enhanced-MRI (DCE-MRI) in the preoperative chemo-radiotherapy (CRT) assessment for locally advanced rectal cancer (LARC) compared to¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT).

Methods

75 consecutive patients with LARC were enrolled in a prospective study. DCE-MRI analysis was performed measuring SIS: linear combination of percentage change (Δ) of maximum signal difference (MSD) and wash-out slope (WOS). ¹⁸F-FDG PET/CT analysis was performed using SUV maximum (SUV_max). Tumor regression grade (TRG) were estimated after surgery. Non-parametric tests, receiver operating characteristic were evaluated.

Results

55 patients (TRG1-2) were classified as responders while 20 subjects as non responders. ΔSIS reached sensitivity of 93%, specificity of 80% and accuracy of 89% (cut-off 6%) to differentiate responders by non responders, sensitivity of 93%, specificity of 69% and accuracy of 79% (cut-off 30%) to identify pathological complete response (pCR). Therapy assessment via ΔSUV_max reached sensitivity of 67%, specificity of 75% and accuracy of 70% (cut-off 60%) to differentiate responders by non responders and sensitivity of 80%, specificity of 31% and accuracy of 51% (cut-off 44%) to identify pCR.

Conclusions

CRT response assessment by DCE-MRI analysis shows a higher predictive ability than ¹⁸F-FDG PET/CT in LARC patients allowing to better discriminate significant and pCR.

Magnetic Resonance Imaging Evaluation in Neoadjuvant Therapy of Locally Advanced Rectal Cancer: A Systematic Review

Background

The aim of the study was to present an update concerning several imaging modalities in diagnosis, staging and pre-surgery treatment response assessment in locally advanced rectal cancer (LARC). Modalities include: traditional morphological magnetic resonance imaging (MRI), functional MRI such as dynamic contrast enhanced MRI (DCE-MRI) and diffusion weighted imaging (DWI). A systematic review about the diagnostic accuracy in neoadjuvant therapy response assessment of MRI, DCE-MRI, DWI and Positron Emission Tomography/Computed Tomography (PET/CT) has been also reported.

Methods

Several electronic databases were searched including PubMed, Scopus, Web of Science, and Google Scholar. All the studies included in this review reported findings about therapy response assessment in LARC by means of MRI, DCE-MRI, DWI and PET/CT with details about diagnostic accuracy, true and false negatives, true and false positives. Forest plot and receiver operating characteristic (ROC) curves analysis were performed. Risk of bias and the applicability at study level were calculated.

Results

Twenty-five papers were identified. ROC curves analysis demonstrated that multimodal imaging integrating morphological and functional MRI features had the best accuracy both in term of sensitivity and specificity to evaluate preoperative therapy response in LARC. DCE-MRI following to PET/CT showed high diagnostic accuracy and their results are also more reliable than conventional MRI and DWI alone.

Conclusions

Morphological MRI is the modality of choice for rectal cancer staging permitting a correct assessment of the disease extent, of the lymph node involvement, of the mesorectal fascia and of the sphincter complex for surgical planning. Multimodal imaging and functional DCE-MRI may also help in the assessment of treatment response allowing to guide the surgeon versus conservative strategies and/or tailored approach such as “wait and see” policy.

MRI for Assessing Response to Neoadjuvant Therapy in Locally Advanced Rectal Cancer Using DCE-MR and DW-MR Data Sets: A Preliminary Report

To evaluate MRI for neoadjuvant therapy response assessment in locally advanced rectal cancer (LARC) using dynamic contrast enhanced-MRI (DCE-MRI) and diffusion weighted imaging (DWI), we have compared magnetic resonance volumetry based on DCE-MRI (V(DCE)) and on DWI (V(DWI)) scans with conventional T2-weighted volumetry (V(C)) in LARC patients after neoadjuvant therapy. Twenty-nine patients with LARC underwent MR examination before and after neoadjuvant therapy. A manual segmentation was performed on DCE-MR postcontrast images, on DWI (b-value 800 s/mm²), and on conventional T2-weighted images by two radiologists. DCE-MRI, DWI, and T2-weigthed volumetric changes before and after treatment were evaluated. Nonparametric sample tests, interobserver agreement, and receiver operating characteristic curve (ROC) were performed. Diagnostic performance linked to DCE-MRI volumetric change was superior to T2-w and DW-MRI volumetric changes performance (specificity 86%, sensitivity 93%, and accuracy 93%). Area Under ROC (AUC) of V(DCE) was greater than AUCs of V(C) and V(DWI) resulting in an increase of 15.6% and 11.1%, respectively. Interobserver agreement between two radiologists was 0.977, 0.864, and 0.756 for V(C), V(DCE), and V(DWI), respectively. V(DCE) seems to be a promising tool for therapy response assessment in LARC. Further studies on large series of patients are needed to refine technique and evaluate its potential value.

Standardized Index of Shape (SIS): a quantitative DCE-MRI parameter to discriminate responders by non-responders after neoadjuvant therapy in LARC

OBJECTIVES

To investigate the potential of DCE-MRI to discriminate responders from non-responders after neoadjuvant chemo-radiotherapy (CRT) for locally advanced rectal cancer (LARC). We investigated several shape parameters for the time-intensity curve (TIC) in order to identify the best combination of parameters between two linear parameter classifiers.

METHODS

Seventy-four consecutive patients with LARC were enrolled in a prospective study approved by our ethics committee. Each patient gave written informed consent. After surgery, pathological TNM and tumour regression grade (TRG) were estimated. DCE-MRI semi-quantitative analysis (sqMRI) was performed to identify the best parameter or parameter combination to discriminate responders from non-responders in response monitoring to CRT. Percentage changes of TIC shape descriptors from the baseline to the presurgical scan were assessed and correlated with TRG. Receiver operating characteristic analysis and linear classifier were applied.

RESULTS

Forty-six patients (62.2%) were classified as responders, while 28 subjects (37.8%) were considered as non-responders. sqMRI reached a sensitivity of 93.5% and a specificity of 82.1% combining the percentage change in Maximum Signal Difference (ΔMSD) and Wash-out Slope (ΔWOS), the Standardized Index of Shape (SIS).

CONCLUSIONS

SIS obtains the best result in discriminating responders from non-responders after CRT in LARC, with a cut-off value of -3.0%.

KEY POINTS

• DCE-MRI shape descriptors are investigated to assess preoperative CRT response in LARC. • Identification of the best TIC shape descriptors combination through a linear classifier. • Identification of a single MRI index to predict neoadjuvant treatment response.

Magnetic iron oxide nanoparticles for biomedical applications

Due to their high magnetization, superparamagnetic iron oxide nanoparticles induce an important decrease in the transverse relaxation of water protons and are, therefore, very efficient negative MRI contrast agents. The knowledge and control of the chemical and physical characteristics of nanoparticles are of great importance. The choice of the synthesis method (microemulsions, sol-gel synthesis, laser pyrolysis, sonochemical synthesis or coprecipitation) determines the magnetic nanoparticle's size and shape, as well as its size distribution and surface chemistry. Nanoparticles can be used for numerous in vivo applications, such as MRI contrast enhancement and hyperthermia drug delivery. New developments focus on targeting through molecular imaging and cell tracking.