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Prediction of N0 Irradiated Rectal Cancer Comparing MRI Before and After Preoperative Chemoradiotherapy.

By: Fabio Pomerri, Filippo Crimì, Nicola Veronese, Alessandro Perin, Carmelo Lacognata, Francesca Bergamo, Caterina Boso, Isacco Maretto

1 Department of Medicine, Institute of Radiology, University of Padova, Padova, Italy 2 Department of Medicine, Geriatric Section, University of Padova, Padova, Italy 3 Department of Surgery, Oncology and Gastroenterology, University of Padova, Padova, Italy 4 Department of Radiology, Azienda Ospedaliera of Padova, Padova, Italy 5 Medical Oncology 1, Istituto Oncologico Veneto Istituto di Ricovero e Cura a Carattere Scientifico, Padova, Italy 6 Radiation Oncology, Istituto Oncologico Veneto Istituto di Ricovero e Cura a Carattere Scientifico, Padova, Italy.
2017-10-10; doi: 10.1097/DCR.0000000000000894

Abstract

Background

The prediction of lymph node status using MRI has an impact on the management of rectal cancer, both before and after preoperative chemoradiotherapy.

Objective

The purpose of this study was to maximize the negative predictive value and sensitivity of mesorectal lymph node imaging after chemoradiotherapy because postchemoradiation node-negative patients may be treated with rectum-sparing approaches.

Design

This was a retrospective study.

Settings

The study was conducted at a tertiary care hospital.

Patients

Sixty-four patients with locally advanced rectal cancer who underwent preoperative chemoradiotherapy and MRI for staging and the assessment of response were evaluated.

Main

The sums of the sizes of all mesorectal lymph nodes in each patient on both prechemoradiotherapy and postchemoradiotherapy imaging data sets were calculated to determine the lymph node global size reduction rates, taking these to be the outcomes of the histopathologic findings. Other included measures were interobserver agreement regarding the prediction of node status based on morphologic criteria and the diagnostic performance of contrast-enhanced images.

Results

Using a cutoff value of a 70% lymph node global size reduction rate with only 15 node-positive patients on histopathology, the sensitivity in the prediction of nodal status and negative predictive value were 93% (95% CI, 70.2%-98.8%) and 97% (95% CI, 82.9%-99.8%) for observer 1 and 100% (95% CI, 79.6%-100%) and 100% (95% CI, 62.9%-100%) for observer 2. The areas under the receiver operating characteristic curves for the 2 observers were 0.90 (95% CI, 0.82-0.98; p < 0.0001) for observer 1 and 0.65 (95% CI, 0.50-0.79; p = 0.08) for observer 2. The efficacy of the morphologic criteria and contrast-enhanced images in predicting node status was limited after chemoradiotherapy.

Limitations

This study is limited by its small sample size and retrospective nature.

Conclusions

Assessing the lymph node global size reduction rate value reduces the risk of undetected nodal metastases and may be helpful in better identifying suitable candidates for the local excision of early stage rectal cancer. See Video Abstract at http://links.lww.com/DCR/A412.

PMID:28991083