| Objective To expore the value of transrectal biplane ultrasound combined with elastography and contrast-enhanced ultrasonography in the assessment of curative effect of neoadjuvant chemoradiotherapy for rectal cancers,and to evaluate its accuracy in preoperative staging of rectal cancers after radiotherapy and chemotherapy.Methods Altogether 53 patients with advanced low rectal cancers were involved as the object of this research.Firstly,routine biplane transrectal ultrasonography(TRUS)was performed in all the patients before and after neoadjuvant chemotherapy to observe the shape,internal echo,and boundary and blood flow distribution of colorectal tumors.The parameters of conventional ultrasound examinations were recorded,including the distance from the lower part of the mass to the anal verge,lump diameter and thickness,the peak systolic velocity(PSV),resistance index(RI)and tumor vascular grading,so as to make a preliminary staging of rectal cancers and observe the surrounding lymph nodes;then,transrectal elastography(UE)was performed in rectal cancer patients;according to the elastic image of colorectal tumors,the mass boundary was further determined;the mass elasticity score was made and the strain ratio(SR)of the mass was measured;then,the rectal cancer patients underwent contrast-enhanced ultrasound(CEUS);the internal contrast agent enhanced features of colorectal tumors and the relationship between the tumor enhancement area and intestinal wall enhancement levels were observed;the contrast images were analyzed offline to obtain the perfusion time intensity curve(TIC)in the region of interest(ROI);and the following parameters were obtained from the curve,such as peak intensity(PI)and area under the curve(AUC)and time to peak(TTP);finally,through comprehensive analysis,the colorectal tumors were staged as T and N staging.The ultrasonic parameters and colorectal ultrasound changes in T staging before and after neoadjuvant chemotherapy as well as preoperative ultrasound measurement of the distance from the lower part of the mass to the anal verge,the mass diameter,thickness and their correlation with corresponding intraoperative values were analyzed and compared.The colorectal pathological staging was made postoperatively to calculate the number of cases in each period of pT and pN.The postoperative pathologic staging was taken as the gold standard to analyze the consistency between the preoperative staging and postoperative pathological staging of rectal cancers by using TRUS combined with UE and CEUS after radiotherapy and chemotherapy.Additionally,the number of understaging and overstaging cases,the preoperative staging accuracy,sensitivity,specificity,positive predictive value and negative predictive value were calculated.Results 1.The average mass diameter and thickness of rectal cancers after neoadjuvant chemoradiotherapy were reduced in different degrees in contrast with those before neoadjuvant chemoradiotherapy,with statistically significant difference(P<0.05);no statistically significant difference was found in the distance from the lower part of the mass to the anal verge(P>0.05)before and after radiotherapy and chemotherapy.According to the transrectal ultrasonography,the diameter,thickness and the distance from the lower part of the mass to the anal verge after neoadjuvant chemoradiotherapy showed no statistically significant difference with intraoperative ones(P>0.05)and were positively correlated(the correlation coefficients were 0.784,0.967 and 0.989 respectively,P<0.05).Color Doppler showed that PSV and RI values in colorectal tumor internal blood flow distribution after neoadjuvant chemotherapy were reduced in different degrees in comparison with those before neoadjuvant chemotherapy,with statistically significant difference(P<0.05).The vascular grade of rectal tumors decreased from Grade Ⅱ and Ⅲ before radiotherapy and chemotherapy to Grade 0 and I after radiotherapy and chemotherapy,with statistically significant difference(P<0.05).2.The hardness of the mass in Rectal Cancer Group after neoadjuvant chemoradiotherapy was less than that before neoadjuvant chemoradiotherapy,with significant difference between the two groups(P<0.05).The mean SR of rectal cancers before radiotherapy and chemotherapy was 4.40±0.57;while,the mean ultrasonic elastic SR of rectal cancers after radiotherapy and chemotherapy was 2.62±0.70,with statistically significant difference between the two groups(P<0.05).3.The overall contrast enhancement ultrasound pattern of rectal cancers was fast-in and fast-out.Through quantitative analysis of ROI in contrast-enhanced ultrasound,it was found that the PI and AUC after neoadjuvant chemotherapy were reduced compared with those before neoadjuvant chemotherapy,with statistically significant difference(P<0.05);while,increased TTP was seen after neoadjuvant chemotherapy,with statistically significant difference(P<0.05).4.Rectal cancers in T staging were understaged after radiotherapy and chemotherapy compared with those before neoadjuvant chemoradiotherapy,with statistically significant difference(P<0.05).The postoperative understaging rate was 39.6%(21/53).The accuracy rate by using TRUS combined with UE and CEUS in evaluation of T staging for rectal cancers after neoadjuvant chemoradiotherapy was 84.9%,highly consistent with that by using pathological T staging(Kappa=0.768,P<0.05);its sensitivity and specificity in the diagnosis of rectal cancers ranging from T0 to T4 were 80.0%,50.0%,75.0%,96.3%,100%and 95.4%,97.9%,95.1%,88.5%,100%,respectively.The total accuracy rate by using TRUS combined with UE and CEUS in evaluation of N staging for rectal cancers after neoadjuvant chemoradiotherapy was 67.9%(36/53),poor consistent with that by using pathological N staging(Kappa=0.225,P>0.05).Its sensitivity and specificity in the diagnosis of rectal cancers in N staging were 43.8%and 78.4%,respectively.Conclusion 1.Conventional biplane transrectal ultrasound can accurately judge the tumor size and the distance from the lower part of the tumor to the anal verge of rectal cancers after neoadjuvant chemoradiotherapy,and also can reflect changes in tumor size and blood flow in the tumor before and after neoadjuvant chemotherapy,which provide a reliable basis for the evaluation of the efficacy of neoadjuvant chemoradiotherapy for rectal cancers and guiding the surgical treatment.2.Transrectal elastography(UE)can more accurately assist the conventional ultrasound in preoperative staging of rectal cancers.The UE elasticity score method and SR ratio method can better reflect the changes of the hardness of colorectal tumors before and after neoadjuvant chemotherapy,thereby making up for the deficiency of conventional ultrasound and providing more abundant information for the diagnosis of the disease.3.Contrast-enhanced transrectal ultrasound(CEUS)can intuitively reflect the microvascular perfusion of rectal cancers so as to provide more useful information for preoperative staging of rectal cancers.Ultrasound contrast parameters that reflect vascular changes of rectal cancers,such as PI,AUC and TTP,can be used as a favorable method to evaluate the efficacy of radiotherapy and chemotherapy.4.Conventional transrectal ultrasound is still the main assessment approach for preoperative staging of rectal cancers;while,conventional ultrasonography can be assisted with elasticity imaging and contrast-enhanced ultrasound,the combination of which can make preoperative T staging of rectal cancers after neoadjuvant chemoradiotherapy in a more accurate manner,and also can well reflect the change in the depth of invasion for rectal cancers before and after neoadjuvant chemotherapy,suggesting the treatment effect of neoadjuvant chemotherapy.5.TRUS combined with UE and CEUS is not ideal yet in accurate evaluation of preoperative N staging of rectal cancers after neoadjuvant chemoradiotherapy.It should be combined with CT or MRI imaging techniques to make a comprehensive evaluation.It is still difficult to obtain a satisfactory elastic image in some cases with application of ultrasound elastography in the diagnosis of rectal cancers,which may affect the accuracy of transrectal ultrasound elastography in the evaluation of rectal cancers. |
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