Correlation of the tumour-stroma ratio with diffusion weighted MRI in rectal cancer

Stéphanie M Zunder,Raquel Perez-Lopez,Bente M De Kok,Maria Vittoria Raciti,Gabi W Van Pelt,Rodrigo Dienstmann,Alonso Garcia-Ruiz,C Arnoud Meijer,Hans Gelderblom,Rob A Tollenaar,Paolo Nuciforo,Martin N Wasser,Wilma E Mesker

doi:10.1016/j.ejrad.2020.109345

Abstract

ObjectiveThis study evaluated the correlation between intratumoural stroma proportion, expressed as tumour-stroma ratio (TSR), and apparent diffusion coefficient (ADC) values in patients with rectal cancer. MethodsThis multicentre retrospective study included all consecutive patients with rectal cancer, diagnostically confirmed by biopsy and MRI. The training cohort (LUMC, Netherlands) included 33 patients and the validation cohort (VHIO, Spain) 69 patients. Two observers measured the mean and minimum ADCs based on single-slice and whole-volume segmentations. The TSR was determined on diagnostic haematoxylin & eosin stained slides of rectal tumour biopsies. The correlation between TSR and ADC was assessed by Spearman correlation (rs). ResultsThe ADC values between stroma-low and stroma-high tumours were not significantly different. Intra-class correlation (ICC) demonstrated a good level of agreement for the ADC measurements, ranging from 0.84–0.86 for single slice and 0.86–0.90 for the whole-volume protocol. No correlation was observed between the TSR and ADC values, with ADCmeanrs= -0.162 (p= 0.38) and ADCminrs= 0.041 (p= 0.82) for the single-slice and rs= -0.108 (p= 0.55) and rs= 0.019 (p= 0.92) for the whole-volume measurements in the training cohort, respectively. Results from the validation cohort were consistent; ADCmeanrs= -0.022 (p= 0.86) and ADCminrs = 0.049 (p= 0.69) for the single-slice and rs= -0.064 (p= 0.59) and rs= -0.063 (p= 0.61) for the whole-volume measurements. ConclusionsReproducibility of ADC values is good. Despite positive reports on the correlation between TSR and ADC values in other tumours, this could not be confirmed for rectal cancer.

Highlights

Colorectal cancer is the third most common cancer in Europe, with approximately 30% of these cancers arising from the rectum [1]
The aim of this study is to evaluate whether there is a corre lation between the intratumoural stroma proportion (i.e. tumour-stroma ratio (TSR)) and apparent diffusion coefficient (ADC) values as derived from magnetic resonance imaging (MRI)-diffusionweighted imaging (DWI), in order to determine if there is po tential for this parameter as biomarker for clinical decision making with respect to neoadjuvant treatment and patient follow-up
Noteworthy to mention, Vall d’Hebron University Hospital included DWI in the standard protocol for rectal cancer in 2011, whereas the LUMC started with incorporation in 2015, which influenced the sample size of the training and validation cohort

Summary

Introduction

Colorectal cancer is the third most common cancer in Europe, with approximately 30% of these cancers arising from the rectum [1]. Cur rent European guidelines on rectal cancer recommend performing a pelvic magnetic resonance imaging (MRI) scan for locoregional staging, in order to predict the risk of synchronous and metachronous distant metastases, and to select the appropriate treatment [2]. MRI is the cornerstone of rectal cancer management. Tumour masses are pathologically complex structures, which can consist of almost up to 50 percent of stroma cells, wherein cancer-associated fibroblasts, immune cells and angiogenic vascular cells create an activated tumour microenvironment, promoting tumour progression, angiogenesis, invasion and metastasis [3,4,5]. Microscopic quantification of the amount of intratumoural stroma, referred to as the tumour-stroma ratio (TSR), has proven to be prognostic in various solid tumours [6,7,8,9,10,11,12,13], wherein a high proportion of intratumoural stroma is associated with a poor prognosis

Methods

Discussion

Conclusion