Comparison of diffusion‐weighted MRI and MR volumetry in the evaluation of early treatment outcomes after preoperative chemoradiotherapy for locally advanced rectal cancer

Abstract

Purpose: To compare diffusion-weighted imaging (DWI) and magnetic resonance (MR) volumetry for predicting treatment outcomes of locally advanced rectal cancers with preoperative chemoradiotherapy (CRT). Materials and Methods:This prospective study was approved by our Institutional Review Board. Thirty-four patients underwent three MR examinations: pre-CRT (before CRT), early CRT (2 weeks after CRT initiation), and post-CRT (before surgery). The tumor apparent diffusion coefficient (ADC), ADC increase rate, and volume reduction rate were compared between responders and nonresponders using three reference standards: downstaging, modified Response Evaluation Criteria in Solid Tumors (mRECIST), and tumor regression grade (TRG). For DWI and volumetry, differences between responders and nonresponders were assessed by receiver operating characteristic analysis.Results: The median early tumor volume reduction rate of responders, subgrouped by downstaging and mRECIST (47.97% and 53.97%, respectively), was significantly higher than that of nonresponders (20.94% and 20.36%; P ¼ 0.0024 and 0.0001, respectively), but there were no significant differences in pre-CRT ADC and early ADC increase rate using all references. When using the downstaging and mRECIST, the diagnostic performance of early tumor volume reduction rate (Az ¼ 0.81 and 0.94, respectively) was higher than that of pre-CRT ADC (Az ¼ 0.55 and 0.62; P ¼ 0.033 and 0.007) and early ADC increase rate (Az ¼ 0.58 and 0.64; P ¼ 0.055 and 0.01) for predicting the treatment outcome. For TRG, there were no significant differences between DWI and volumetry.Conclusion: Early tumor volume reduction rate at the second week after CRT initiation may be a better indicator than DWI based on the mean ADC measurements for predicting CRT treatment outcome.

Diffusion-weighted MR imaging of the rectum: Clinical applications

“…A few authors advocate the use of bowel preparation based on rectal suppository laxatives [10,12,16]. Several studies have reported the use of intravenous administration of spasmolytic agents to reduce bowel peristalsis, which may be particularly useful at 3 T MR imaging [11][12][13]16,18].…”

“…Early publications concerning application of DW-MRI to rectal disease mainly dealt with evaluation of tumor response to treatment [3][4][5][6]. Since then, rectal DW-MRI has become a feasible option and several groups have confirmed early encouraging results in the area of rectal disease detection [7][8][9] or tumoral response evaluation [3,8,[10][11][12][13][14][15][16][17][18][19][20]. Recent guidelines for rectal cancer imaging even recommend DW-MRI as part of a standard MR imaging protocol for preoperative restaging of rectal cancers after neoadjuvant chemoradiotherapy (CRT) [21].…”

Combined T2w volumetry, DW-MRI and DCE-MRI for response assessment after neo-adjuvant chemoradiation in locally advanced rectal cancer

“…In multiple studies it was shown that T2-weighted (T2w) MRI tumor volume reduction was predictive for pathological response after neo-adjuvant therapy [5][6][7][8]. Besides, also several studies showed that functional MR imaging is helpful for response prediction after neo-adjuvant therapy.…”

2035 Diffusion-weighted magnetic resonance imaging for the prediction of the tumor response to neoadjuvant chemoradiotherapy using irinotecan plus S-1 for rectal cancer

“…Lambregts et al (28) previously reported that the quantitative evaluation of the ADC may be used as a biomarker for the response to treatment. The diagnostic performance of the ADC with various cut-off values ranging between 1.2 and 1.4 x10 3 mm 2 /sec in RC has been reported to be equivalent to ~46-100% sensitivity and ~56-84% specificity (18,19,21,29). The value of DW-MRI as a predictive tool for assessing response to NA-CRT in patients with RC is currently poorly understood.…”

“…It appears that necrotic areas with high pretreatment ADC values may be less sensitive to CRT. However, several studies have produced contradictory results (29,30). Previously published data on the value of DW-MRI as a predictive tool for anticancer treatment responses in patients with RC are scarce and conflicting.…”