MRI morphologic and clinicopathologic characteristics for predicting outcomes in patients with locally advanced rectal cancer

Oncologic Outcomes Associated With MRI-detected Extramural Venous Invasion (mrEMVI) in Rectal Cancer: A Systematic Review and Meta-analysis

BACKGROUND

The role of MRI-detected EMVI (mrEMVI) as a reliable prognostic factor in rectal cancer has been emphasized in recent years but this finding remains underreported by many institutions.

OBJECTIVE

This review aimed to demonstrate the importance of pre- and post-treatment MRI-detected EMVI as independent prognostic factors of adverse oncologic outcomes in patients undergoing neoadjuvant therapy followed by total mesorectal excision.

METHODS

This review was designed using the PRISMA guidelines. The following electronic databases were searched from January 2002 to January 2020: CENTRAL, Ovid MEDLINE, PubMed, and Ovid Embase. Main outcomes included DFS and overall survival (OS). Other outcomes of interest comprised positive resection margin and synchronous metastases.

RESULTS

Seventeen studies involving a total of 3821 patients were included for data synthesis. For preneoadjuvant treatment mrEMVI, pooled hazard ratio (HR) estimate for DFS was 2.30 (95% confidence intervals (CI) 1.54-3.44) for higher recurrence in mrEMVI-positive patients. mrEMVI-positive patients were found to have a lower OS with a pooled HR of 1.68 (95%CI 1.27-2.22). Pooled risk ratio for synchronous metastasis was 4.11 (95%CI 2.80-6.02) for mrEMVI-positivity. For postneoadjuvant treatment EMVI (ymrEMVI), positive status showed a lower DFS with a pooled HR of 2.04 (95%CI 1.55-2.69). Risk ratio of having a positive resection margin status was 2.95 (95%CI 1.75-4.98) for ymrEMVI-positive patients.

CONCLUSIONS

This review showed that oncologic outcomes are significantly worse for both pre- and post-neoadjuvant treatment mrEMVI-positive patients. MRI-detected EMVI should be consistently reported in rectal cancer staging and may provide guidance for the targeted use of additional systemic therapy.

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.

Prognostic Importance of MRI-Detected Extramural Venous Invasion in Rectal Cancer: A Literature Review and Systematic Meta-Analysis

PURPOSE

Extramural venous invasion (EMVI) is recognized as a poor prognostic factor in rectal cancer. There are well-documented limitations associated with pathology detection of EMVI, including variable reporting and the inability to use it preoperatively to guide neoadjuvant treatment. Magnetic resonance imaging (MRI)-detected EMVI (mrEMVI) has been proposed as an imaging biomarker. This review assesses the prognostic significance of mrEMVI on survival outcomes and whether regression of mrEMVI after neoadjuvant therapy is associated with improvements in survival.

METHODS AND MATERIALS

An electronic search was carried out using MEDLINE and EMBASE databases using the search terms "rectum," "cancer,", "MRI," and "outcomes." A systematic review and meta-analysis were carried out in accordance with Preferred Reporting for Systematic Reviews and Meta-Analyses guidelines using Review Manager software. A qualitative review was performed.

RESULTS

A total of 7399 articles were identified, of which 33 were relevant to the review question. After a qualitative assessment, 20 articles were included in the meta-analysis. Baseline mrEMVI positivity is associated with significantly worsened overall survival (hazard ratio [HR] 1.84; 95% confidence interval [CI], 1.33-2.54; P = .0001) and significantly worsened disease-free survival (HR 2.41; 95% CI, 2.02-2.89; P < .00001). After neoadjuvant treatment, a positive mrEMVI status is associated with a significantly worsened overall and disease-free survival. Only 3 papers specifically looked at mrEMVI regression, but the results show that persistent mrEMVI-positive status after treatment is associated with significantly worsened disease-free survival compared with a change in mrEMVI from positive to negative (HR 1.93; 95% CI, 1.39-2.68; P < .0001). A subgroup analysis of MRI-detected lymph node metastases showed no significant association with survival, with a hazard ratio of 1.33 (95% CI, 0.98-1.80; P = .06).

CONCLUSION

mrEMVI is significantly associated with worsened survival outcomes, both at baseline and after neoadjuvant treatment. Additionally, there is evidence that regression of mrEMVI after neoadjuvant treatment is associated with improved survival compared with mrEMVI persistence. The findings of this review emphasize the need for accurate and consistent reporting of mrEMVI status before and after neoadjuvant treatment and support the inclusion of mrEMVI into staging systems preferentially over lymph node metastases.

The prognostic value of MRI-detected extramural vascular invasion (mrEMVI) for rectal cancer patients treated with neoadjuvant therapy: a meta-analysis

OBJECTIVES

The purpose of this meta-analysis was to evaluate the prognostic value of MRI-detected extramural vascular invasion (mrEMVI) and mrEMVI after neoadjuvant therapy (ymrEMVI) in rectal cancer patients receiving neoadjuvant therapy.

METHODS

A systematic search of the PubMed, Web of Science, Embase, and Cochrane Library databases was carried out up to June 2020. Studies that evaluated mrEMVI, used treatment with neoadjuvant therapy, and reported survival were included. The time-to-event outcomes (OS and DFS rates) are expressed as hazard ratios (HRs) with 95% confidence intervals (CIs). If the HR was not reported in the study, it was calculated from the survival curve using methods according to Parmar's recommendation. The Newcastle-Ottawa scale was used to assess the methodological quality of the studies included in the meta-analysis.

RESULTS

A total of 2237 patients from 11 studies were included, and the pooled analysis of the overall results from eight studies showed that patients who were mrEMVI positive at baseline had significantly worse disease-free survival (DFS) (random-effects model: HR = 2.50 [1.84, 3.14]; Z = 5.83, p < 0.00001). The pooled analysis of the overall results from six studies showed that patients who were ymrEMVI positive following neoadjuvant therapy had significantly worse DFS (random-effects model: HR = 2.24 [1.73, 2.90], Z = 6.12, p < 0.00001). Patients with mrEMVI positivity at baseline were also associated with worse overall survival (OS) (random-effects model: HR = 1.93 [1.36, 2.73]; Z = 3.71, p < 0.00001).

CONCLUSION

mrEMVI and ymrEMVI positivity are poor prognostic factors for rectal cancer patients treated with neoadjuvant therapy. The precise evaluation of EMVI may contribute to designing individualised treatments and improving patient outcomes.

KEY POINTS

• Extramural vascular invasion (EMVI) is a prognostic factor for rectal cancer. • MRI can be used to evaluate EMVI status before (mrEMVI) and after neoadjuvant therapy (ymrEMVI). • The evaluation of mrEMVI and ymrEMVI in neoadjuvant therapy would provide an early assessment of patient prognosis.

MRI radiomics in the prediction of therapeutic response to neoadjuvant therapy for locoregionally advanced rectal cancer: a systematic review

Introduction: The standard of care for locoregionally advanced rectal cancer is neoadjuvant therapy (NA CRT) prior to surgery, of which 10-30% experience a complete pathologic response (pCR). There has been interest in using imaging features, also known as radiomics features, to predict pCR and potentially avoid surgery. This systematic review aims to describe the spectrum of MRI studies examining high-performing radiomic features that predict NA CRT response.Areas covered: This article reviews the use of pre-therapy MRI in predicting NA CRT response for patients with locoregionally advanced rectal cancer (T3/T4 and/or N1+). The primary outcome was to identify MRI radiomic studies; secondary outcomes included the power and the frequency of use of radiomic features.Expert opinion: Advanced models incorporating multiple radiomics categories appear to be the most promising. However, there is a need for standardization across studies with regards to; the definition of NA CRT response, imaging protocols, and radiomics features incorporated. Further studies are needed to validate current radiomics models and to fully ascertain the value of MRI radiomics in the response prediction for locoregionally advanced rectal cancer.

Preoperative concurrent chemoradiotherapy MRI characteristics favouring pathologic complete response in patients with rectal cancer: Usefulness of MR T2-stage as an ancillary finding for predicting pathologic complete response

INTRODUCTION

This study sought to assess preoperative concurrent chemoradiotherapy (CRT) magnetic resonance imaging (MRI)-based findings according to a structured MRI report template for primary staging of rectal cancer, and to evaluate the prognostic relevance of the pre-CRT MRI-based findings in patients with rectal cancer after CRT.

METHODS

We retrospectively evaluated pre- and post-CRT MRI data of patients with pathologically proven rectal adenocarcinoma, between January 2008 and October 2019. Image interpretation was performed independently by two radiologists and each reviewer assessed the cancer characteristics on MRI, based on the structured MRI report for primary staging. MRI-based findings associated with pathologic complete tumour regression grade (TRG) after CRT were analysed by univariate and multivariate analysis. Significant factors from pre-CRT MRI were weighted to score mrTRG in post-CRT MRI.

RESULTS

On univariate analysis, MR T-stage, tumour infiltration, mesorectal fascia involvement, extramural vascular invasion and serum carcinoembryonic antigen level correlated significantly with pathologic complete response (pCR). Multivariate analysis identified that only MR T-stage was independently associated with pCR (odds ratio, 3.89, 95% confidence interval, 1.18-12.84; P = 0.0278). Adding MRI-based T2-stage as an ancillary finding to mrTRG statistically significantly improved the sensitivity as compared to using only mrTRG for considering a CR. T2_mrTRG was significantly different in terms of the time to tumour progression between the CR and non-CR group.

CONCLUSIONS

The MR T2-stage was independently associated with pCR after CRT in patients with rectal cancer and was helpful as ancillary predictive factor, adding to mrTRG for prediction of pCR.