The role of readout-segmented echo-planar imaging-based diffusion-weighted imaging in evaluating tumor response of locally advanced rectal cancer after neoadjuvant chemoradiotherapy. (September 2020)

• Record Type: Journal Article
• Authors: Yang, Lanqing; Xia, Chunchao; Liu, Dan; Fang, Xin; Pan, Xuelin; Ma, Ling; Wu, Bing
• Is Part Of: Acta radiologica. Volume 61:Number 9(2020)
• Page Start: 1155
• Page End: 1164
• Publication Date: 2020-09
• Subjects: Rectal neoplasms -- neoadjuvant therapy -- magnetic resonance imaging -- diffusion magnetic resonance imaging; Radiology, Medical -- Periodicals; Radiography, Medical -- Periodicals; Radiotherapy -- Periodicals; 616.0757
• DOI: 10.1177/0284185119897354
• Languages: English
• ISSNs: 0284-1851

Abstract

Background: Accurate assessment of tumor response in rectal cancer could help individualize treatment. Purpose: To evaluate the role of diffusion-weighted imaging (DWI) based on readout-segmented echo-planar imaging (rs-EPI) in assessing tumor response after neoadjuvant chemoradiotherapy (CRT) in locally advanced rectal cancer (LARC). Material and Methods: Sixty-three patients with LARC who received neoadjuvant CRT and surgery were enrolled retrospectively. They all underwent pre- and post-CRT magnetic resonance examinations, including DWI using rs-EPI. According to pathological results, patients were grouped as pathological complete responder (pCR, n = 16) and non-pCR (n = 47). Visual assessment of residual tumor and whole-tumor histogram analysis of pre- and post-CRT apparent diffusion coefficient (ADC) map was performed by two radiologists; tumor volume on ADC map was also recorded. Results: Overall inter-observer agreement was good for histogram analysis (ICC = 0.543–0.999). Tumor volume reduction rate on ADC map showed no significant difference between the two groups ( P = 0.468). Post-CRT mean, quantile values, and their percentage changes were higher in the pCR group (all P < 0.001). Post-CRT mean value had a good diagnostic power in selecting pCR (AUC = 0.855), with a cut-off value of 1.345 × 10 −3 mm 2 /s, yielding a sensitivity of 83%, specificity of 81.3%. Post-CRT 95% quantile value had the highest AUC (AUC = 0.868) among quantile values, and a higher specificity (87.5% vs. 81.3%) than mean value with comparable overall diagnostic performance ( P = 0.563). Visual assessment showed a sensitivity of 85.1%, specificity of 68.8% in selecting pCR. Conclusion: Quantitative ADC value of rs-EPI DWI could reliably evaluate tumor response in patients with LARC. Post-CRT 95% quantile ADC value could help mean value to more accurately identify pCR.