Application Of Transrectal Ultrasound Elastography In Diagnosis Of Rectal Lesions Before Surgery

OBJECTIVE:1. To evaluate the consistency of multiple measurements of strain ratio obtained by endorectal elastography.2. To evaluate the value of endorectal elastography in the diagnosis of malignant rectal adenoma with the application of elasticity score and strain ratio measurement, and compare it with conventional ERUS and colonoscopic biopsy.3. To investigate the factors affecting the accuracy of endorectal elastography.METHODS:Sixty patients referred to the outpatient clinic of our hospital for the evaluation of rectal adenoma were included in this prospective cohort. The patient underwent endorectal elastography, conventional ERUS and colonoscopic biopsy before operation. The diagnostic values of elasticity score and strain ratio method, were assessed using final operational pathological results as the gold standard, at the same time compared with that of conventional ERUS and colonoscopic biopsy. To evaluate the reproducibility of the strain-ratio measurements, the intraclass correlation coefficient (ICC) was calculated using a one-way random effects model.RESULTS:The reproducibility of the strain-ratio measurements was very good when the averaged triplet measurements were evaluated, with ICC from0.93to0.95. Histopathologically there were20adenomas and40adenocarcinomas. The sensitivity, specificity, accuracy, positive predictive value and negative predictive value of elasticity score were85.0%,70.0%,80.0%,85%and70%, respectively. The strain ratios of adenocarcinomas were significantly higher than that of adenomas(2.82±1.81vs.1.23±0.57, P<0.05). An ROC curve analysis yielded an area under the curve of0.850. The strain ratio cut-off value of1.240was chosen as the probable best cut-off value. The sensitivity, specificity, accuracy, positive predictive value and negative predictive value were82.5%,75.0%,80.0%,86.8%and68.1%, respectively.The diagnostic accuracy of conventional ERUS and colonoscopy biopsy of rectal adenoma were58.3%and63.3%, respectively. The diagnostic accuracy of endorectal elastography was significantly higher than that of the former two(P<0.05). The miss rate of colonoscopic biopsy can be dropped from55%to15%with application of endorectal elastography.The differences of the accuracy of endorectal elastography among different groups of size, location and basement of rectal adenoma were not significant(P>0.05).CONCLUSION:1. Endorectal elasotgraphy can accurately diagnose the malignant rectal adenoma with the application of elasticity score and strain ratio measurement, which can provide reliable preoperative imaging evidence for clinical operation mode.2. The diagnostic accuracy of endorectal elastography was significantly higher than that of conventional ERUS and colonoscopy biopsy. The miss rate of colonoscopy biopsy can be significantly decreased with application of endorectal elastography.3. The reproducibility of strain ratio measurements was good when the averaged triplet measurements were evaluated. More than one measurement can establish a reliable strain ratio value.4. The size, position and basement of rectal adenoma cannot influence the accuracy of endorectal elastography. OBJECTIVE:1. To evaluate the potential of endorectal elastography with strain ratio measurements for monitoring treatment response of locally advanced rectal cancer patients undergoing neoadjuvant therapy.2. To investigate the pathologic mechanism of the changes of SR after neoadjuvant chemoradiotherapy for rectal cancer.METHODS:31patients receiving neoadjuvant therapy had twice examinations of conventional ERUS and endorectal elastography before therapy and then before surgery. Changes in the parameters of strain-ratios were determined and compare the pathologic tumor response after operation. The accuracy of conventional ERUS and endorectal elastography predicting the downstage were compared. Through immunohistochemical AE1/AE3staining the residual tumor of pT1-3rectal cancer after chemoradiotherapy, the relationship between the strain ratio and AE1/AE3marked area of residual tumor was analyzed.RESULTS:29patients (93.5%) demonstrated a significant decrease (p<0.05) in strain ratios, and2patients (6.5%) demonstrated a increase in strain ration. The strain ratios of pT3rectal cancer were significantly higher than that of pT0-2rectal cancer (3.23±0.91vs.2.06±0.86, p<0.05). When the cut-off point of the decreasing amplitude of SR≥34.90, the accuracy of diagnosis of the downstage of pT stage after chemoradiotherapy by endorectal elastography was69%, which is higher than that of the conventional ERUS (45.1%), but the difference was not statistically significant (p<0.05). The conventional ERUS can correctly diagnosis14cases of the downstage increasing from7cases with the decreasing amplitude of SR. The relationship between the SR and AE1/AE3marked area of the residual tumor was linear positive correlation (2.33±1.03vs.43.2±51.6, p<0.05).CONCLUSION:1. Endorectal elastography can demonstrated a significant decrease in strain ratios and the difference in strain ratios of different pT stage, which reflect the changes in internal structure of the lesions after chemoradiotherapy.2. The role of the decreasing amplitude of SR in the diagnosis of clinical downstaging is better than that of conventional ERUS.3. The Endorectal elastography with the decreasing amplitude of SR can assist the conventional ERUS, adds information about the internal biomechnical change after chemoradiotherapy, improve the diagnostic accuracy of the downstage and infiltration depth of the rectal cancer after chemoradiotherapy, thereby providing a new reliable, noninvasive and convenient imaging methods for the assessment of the efficacy and prognosis of the rectal cancer after neoadjuvant chemoradiotherapy.