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The Evaluation of Signal Intensity Related Predictors on T2-weighted for Pathological Complete Response to Neoadjuvant Chemoradiotherapy in Locally Advanced Rectal Cancer1Department of Diagnostic Radiology, National Cancer Center/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China, 2National Cancer Center/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
Synopsis
In order to evaluate the value of tumor signal intensity related parameters on T2-weighted magnetic resonance imaging (MRI) for pathological complete response (pCR) prediction, the signal intensity of tumor(SIT) and the muscle(SIM) were both measured automatically, SIT was defined as an absolute T2W signal intensity of tumor, and SIM was used to correct SIT, resulting in the relative T2W signal intensity(SIT/M), the reduction rate of SIT and SIT/M were calculated.Post-nCRT SIT(SITpost), post-nCRT SIT/M(SIT/Mpost), SITRR and SIT/MRR were proved to be significantly different between pCR and non-pCR, and The diagnositic efficiency is better in non-mucinous adenocarcinoma than mucinous adenocarcinoma.
Introduction
To evaluate the diagnostic performance of tumor signal intensity related parameters on T2-weighted magnetic resonance imaging (MRI) for predicting pathological complete response(pCR) after Neoadjuvant chemoradiotherapy (nCRT) in patients with locally advanced rectal cancer(LARC).Methods
A cohort of 101 patients was examined before and after nCRT. Related parameters of tumor signal intensity on T2-weighted MRI, including Signal Intensity of Tumor(SIT), Signal Intensity of Tumor/Muscle(SIT/M), Signal Intensity of Tumor Reduction Rate(SITRR) and Signal Intensity of Tumor/Muscle Reduction Rate(SIT/MRR) were evaluated by two experienced readers independently. The results of the above parameters of mucinous/non-mucinous adenocarcinoma and only mucinous adenocarcinoma were analyzed statistically.Results
Post-nCRTSIT(SITpost), post-nCRT SIT/M(SIT/Mpost), SITRR and SIT/MRR were proved to be significantly different between pCR and non-pCR before and after exclusion of mucinous adenocarcinoma. The area under the receiver-operating characteristic curve(AUC) of mucinous adenocarcinoma and non-mucinous adenocarcinomafor pCR prediction were 0.694-0.762 and 0.704-0.764 respectively. The corresponding sensitivity and specificity for pCR assessment were 66.2%-78.9% and 63.6%-84.2% respectively. No significant correlation between pre-nCRT T2-weighted signal intensity related parameters and pCR was obtained.Discussion
The change of heterogeneity of tumor tissue and treatment-related fibrosis after nCRT can cause the change of tumor signal intensity on T2-weighted in parents with LARC, and this phenomenon is more pronounced in patients with pCR. In our study, SIT and SIT/M reduced in different degrees after nCRT, SITpost and SIT/Mpost showed significantly different between pCR and non-pCR. In addition, the reduction rate of tumor signal intensity, including SITRR and SIT/MRR, which removed the interference of tumor signal intensity before nCRT, were also proven to be associated with pCR by reader2. Although the results of reader1 indicated that there is no significant difference in SITRR between pCR and non-pCR, in the group without mucinous adenocarcinoma, SITRR was a reliable predictor for pCR. One explanation for this is the mucus lake inside of tumor, which leaded to the reduction of the diagnostic efficiency in mucinous adenocarcinoma.Conclusion
The related parameters of on T2-weighted MRI , including SITpost, SIT/Mpost, SITRR and SIT/MRR are potential predictors for pCR. The diagnositic efficiency is better in non-mucinous adenocarcinoma than mucinous adenocarcinoma.Acknowledgements
Fund programs:Special scientific research projects of public health industry(201402019), Beijing science and technology project（Z161100000516101）, Beijing hope marathon special fund（LC2016A05）References
1. Van Gijn W, Marijnen CA, Nagtegaal ID, et al. Preoperative radiotherapy combined with total mesorectal excision for resectable rectal cancer: 12-year follow-up of the multicentre, randomised controlled TME trial. The Lancet Oncology2011;12(6):575-82.
2. Kim S, Han K, Seo N, et al. T2-weighted signal intensity-selected volumetry for prediction of pathological complete response after preoperative chemoradiotherapy in locally advanced rectal cancer. European radiology 2018.[published Online First:2018/06/03]
Figures
Figure 1. Signal Intensity of Tumor and Signal Intensity of Muscle
The ROI of the tumor (the red curve) and the obturator internus (the yellow curve) were traced at the same slice on oblique axial T2WI.The signal intensity of tumor(SIT) and the muscle(SIM) were both calculated automatically.
Table 1. Distribution of signal intensity related predictors on T2-weighted in the pCR or non-pCR groups for the two readers
pCR: pathological complete response; non-pCR: non-pathological complete response; ICC: inter-observer correlation coefficient; nCRT: neoadjuvant chemoradiotherapy; SITpre: pre-nCRT Signal Intensity of Tumor; SITpost: post-nCRT Signal Intensity of Tumor; SITRR: Signal Intensity of Tumor Reduction Rate; SIT/Mpre: pre-nCRT Signal Intensity of Tumor/Muscle; SIT/Mpost: pre-nCRT Signal Intensity of Tumor/Muscle; SIT/MRR:Signal Intensity of Tumor/Muscle Reduction Rate.a: t-testt; b: Kruskal-Wallis test.
Figure 2. Receiver-operating characteristic curve of selected significant parameters in predicting pCR vs. Non-pCRfor the two readers
(a) Reader1 for all patients; (b) Reader1 for Non-mucinous adenocarcinoma; (c) Reader2 for all patients; (d) Reader2 for Non-mucinous adenocarcinoma.
Table 2. Sensitivity and specificity of Signal Intensity Related Predictors on T2-weighted MRI for Pathological Complete Response
AUC: The area under the receiver-operating characteristic curve; SITpost: post-nCRT Signal Intensity of Tumor; SITRR: Signal Intensity of Tumor Reduction Rate; SIT/Mpost: pre-nCRT Signal Intensity of Tumor/Muscle; SIT/MRR: Signal Intensity of Tumor/Muscle Reduction Rate