Diagnostic performance of MRI for assessment of response to neoadjuvant chemoradiotherapy in oesophageal cancer

Abstract

Background: Patients with a pathological complete response (pCR) after neoadjuvant chemoradiotherapy (nCRT) for oesophageal cancer may benefit from non-surgical management. The aim of this study was to determine the diagnostic performance of visual response assessment of the primary tumour after nCRT on T2-weighted (T2W) and diffusion-weighted (DW) MRI.

Methods: Patients with locally advanced oesophageal cancer who underwent T2W- and DW-MRI (1·5 T) before and after nCRT in two hospitals, between July 2013 and September 2017, were included in this prospective study. Three radiologists evaluated T2W images retrospectively using a five-point score for the assessment of residual tumour in a blinded manner and immediately rescored after adding DW-MRI. Histopathology of the resection specimen was used as the reference standard; ypT0 represented a pCR. Sensitivity, specificity, area under the receiver operating characteristic (ROC) curve (AUC) and interobserver agreement were calculated.

Results: Twelve of 51 patients (24 per cent) had a pCR. The sensitivity and specificity of T2W-MRI for detection of residual tumour ranged from 90 to 100 and 8 to 25 per cent respectively. Respective values for T2W + DW-MRI were 90-97 and 42-50 per cent. AUCs for the three readers were 0·65, 0·66 and 0·68 on T2W-MRI, and 0·71, 0·70 and 0·70 on T2W + DW-MRI (P = 0·441, P = 0·611 and P = 0·828 for readers 1, 2 and 3 respectively). The κ value for interobserver agreement improved from 0·24-0·55 on T2W-MRI to 0·55-0·71 with DW-MRI.

Conclusion: Preoperative assessment of residual tumour on MRI after nCRT for oesophageal cancer is feasible with high sensitivity, reflecting a low chance of missing residual tumour. However, the specificity was low; this results in overstaging of complete responders as having residual tumour and, consequently, overtreatment.

Figure 1

MRI of a patient with locally advanced oesophageal cancer that showed a pathological complete response to neoadjuvant chemoradiotherapy Images from a 55‐year‐old man with a cT3N0 lower oesophageal squamous cell carcinoma, and a complete pathological response after neoadjuvant chemoradiotherapy (nCRT) and oesophagectomy (tumour regression grade 1, ypT0 N0). a–c T2‐weighted (T2W) sagittal (a) and transverse (b) images before chemoradiotherapy show a hyperintense oesophageal wall, accompanied by a hyperintense signal on diffusion‐weighted (DW) imaging (c). d–f T2W sagittal (d) and transverse (e) images after nCRT show a hypointense oesophageal wall, indicating fibrosis; no high signal remained on the corresponding DW image (f). Arrows mark (initial) tumour location.

Figure 2

MRI of a patient with locally advanced oesophageal cancer that showed pathological residual tumour after chemoradiotherapy and surgery Images from a 78‐year‐old man with a cT2 N0 lower oesophageal adenocarcinoma, who had residual tumour after neoadjuvant chemoradiotherapy (nCRT) and oesophagectomy (tumour regression grade 5, ypT2 N0). T2‐weighted (T2W) sagittal (a,d) and transverse (b,e) images before (a,b) and after (d,e) nCRT both show a hyperintense oesophageal wall. The corresponding b = 800 diffusion‐weighted (DW) images before (c) and after (f) nCRT demonstrate a clear hyperintense signal, highly suspicious for tumour. Arrows mark tumour location.

Figure 3

Study flow chart nCRT, neoadjuvant chemoradiotherapy; T2W, T2‐weighted; DW, diffusion‐weighted.

Figure 4

Receiver operating characteristic curves for assessment of residual tumour after neoadjuvant chemoradiotherapy using T2‐weighted MRI and T2‐weighted combined with diffusion‐weighted MRI a Reader 1, b reader 2 and c reader 3. T2W, T2‐weighted; DW, diffusion‐weighted. Comparison of areas under the curve for T2W‐MRI versus T2W + DW‐MRI: a P = 0·441, b P = 0·611, c P = 0·828 (DeLong test33).

Figure 5

MRI of a patient with locally advanced oesophageal cancer located at the gastro‐oesophageal junction Images from an 80‐year‐old man with a cT3 N0 squamous cell carcinoma located at the gastro‐oesophageal junction. Histopathology after oesophagectomy showed residual tumour (tumour regression grade 2, ypT1a N0). a–c T2‐weighted (T2W) sagittal (a) and transverse (b) images before neoadjuvant chemoradiotherapy (nCRT) show a thick hyperintense wall, accompanied by a hyperintense signal on diffusion‐weighted (DW) imaging (c). d–f After nCRT, the T2W images (d,e) show shrinkage of the wall with a mixed hyperintense and hypointense signal, which was assigned a confidence level score of 3 by all readers. The DW image (f) shows spots of hyperintense signal in the primary tumour area (arrow), which is suspicious for residual tumour and was therefore assigned a confidence level score of 4 by all readers. The area within the circle indicates normal stomach wall, which also shows small hyperintense areas on DW imaging. Arrows indicate tumour location.