Diffusion-weighted MRI and 18F-FDG PET/CT in assessing the response to neoadjuvant chemoradiotherapy in locally advanced esophageal squamous cell carcinoma

Abstract

Background: Neoadjuvant chemoradiotherapy (nCRT) followed by surgery is a currently widely used strategy for locally advanced esophageal cancer (EC). However, the conventional imaging methods have certain deficiencies in the evaluation and prediction of the efficacy of nCRT. This study aimed to explore the value of functional imaging in predicting the response to neoadjuvant chemoradiotherapy (nCRT) in locally advanced esophageal squamous cell carcinoma (ESCC).

Methods: Fifty-four patients diagnosed with locally advanced ESCC from August 2017 to September 2019 and treated with nCRT were retrospectively analyzed. DW-MRI scanning was performed before nCRT, at 10-15 fractions of radiotherapy, and 4-6 weeks after the completion of nCRT. ¹⁸F-FDG PET/CT scans were performed before nCRT and 4-6 weeks after the completion of nCRT. These ¹⁸F-FDG PET/CT and DW-MRI parameters and relative changes were compared between patients with pathological complete response (pCR) and non-pCR.

Results: A total of 8 of 54 patients (14.8%) were evaluated as disease progression in the preoperative assessment. The remaining forty-six patients underwent operations, and the pathological assessments of the surgical resection specimens demonstrated pathological complete response (pCR) in 10 patients (21.7%) and complete response of primary tumor (pCR-T) in 16 patients (34.8%). The change of metabolic tumor volume (∆MTV) and change of total lesion glycolysis (∆TLG) were significantly different between patients with pCR and non-pCR. The SUVmax-T_post, MTV-T_post, and TLG-T_post of esophageal tumors in ¹⁸F-FDG PET/CT scans after neoadjuvant chemoradiotherapy and the ∆ SUVmax-T and ∆MTV-T were significantly different between pCR-T versus non-pCR-T patients. The esophageal tumor apparent diffusion coefficient (ADC) increased after nCRT; the ADC_during, ADC_post and ∆ADC_during were significantly different between pCR-T and non-pCR-T groups. ROC analyses showed that the model that combined ADC_during with TLG-T_post had the highest AUC (0.914) for pCR-T prediction, with 90.0% and 86.4% sensitivity and specificity, respectively.

Conclusion: ¹⁸F-FDG PET/CT is useful for re-staging after nCRT and for surgical decision. Integrating parameters of ¹⁸F-FDG PET/CT and DW-MRI can identify pathological response of primary tumor to nCRT more accurately in ESCC.

Keywords: 18F-FDG PET/CT; DW-MRI; Esophageal squamous cell cancer; Neoadjuvant chemoradiotherapy; Pathological complete response.

Fig. 1

Images from a patient with a cT3N1M0 lower thoracic esophageal squamous cell carcinoma with pathological complete response to neoadjuvant chemoradiotherapy. A, B: PET/CT images before nCRT; C, D: PET/CT images five weeks after nCRT; E, G, I: T2 weighted MRI images, F, H, J: DW-MRI images (b value = 800 s/mm²); E, F: before nCRT; G, H: 13 fractions during nCRT; I, J: five weeks after nCRT. PET/CT positron emission tomography/computed tomography; DW-MRI diffusion-weighted magnetic resonance imaging

Fig. 2

ROC curves of the combined model to predict pCR-T. AUC of TLG-T_post: 0.828(95% CI: 0.682–0.925); AUC of ADC_during: 0.880(95%CI: 0.704–0.962); AUC of combined model 0.914(95%CI: 0.759–0.983). TLG total lesion glycolysis; ADC apparent diffusion coefficient; ROC receiver operating characteristic; AUC areas under the curve; CI confidence interval