To investigate the value of endorectal shear wave elastography in T staging of locally advanced rectal cancer after neoadjuvant radiochemotherapy.

Fifty-seven patients with locally advanced rectal cancer who received neoadjuvant chemoradiotherapy and radical surgery were included. The postoperative pathologic results were used as gold standard to evaluate the diagnostic accuracy of endorectal shear wave elastography (SWE) and endorectal ultrasound (ERUS) in T staging of rectal cancer after neoadjuvant radiochemotherapy.

The diagnostic accuracy of ERUS in T staging of locally advanced rectal cancer after neoadjuvant chemoradiotherapy was 59.6% (34/57). The diagnostic accuracy of ERUS in distinguishing whether a tumor was confined to the intestinal wall (T0-T2) was 39.3% (11/28). 46.2% (6/13) of ypT0 patients were over staged. The mean maximum values of the Young's modulus (Emax) of the lesions before and after chemoradiotherapy were (103.27±29.23) kPa and (49.91±32.67) kPa, respectively. The difference was statistically significant (P<0.001). The Emax values increase with T stage after neoadjuvant chemoradiotherapy. Receiver operating characteristic curves were constructed from Emax values of the lesions after neoadjuvant chemoradiotherapy. After calculation, 58 kPa was determined to be the optimized threshold for diagnosing the residual lesions confined to the intestinal wall (ypT0-2) after chemoradiotherapy, and the sensitivity, specificity and accuracy were 76.2%, 86.4%, 78.9%, respectively. 43 kPa was determined to be the optimized threshold for diagnosing no residual tumor in intestinal wall (ypT0) after chemoradiotherapy, and the sensitivity, specificity and accuracy were 100%, 84.6%, 89.7%, respectively, indicating that shear wave elastography can improve the accuracy of rectal cancer restaging after neoadjuvant treatment, which is helpful for clinical decision making.

Endorectal SWE can improve the diagnostic efficacy of T staging in locally advanced rectal cancer after neoadjuvant chemoradiotherapy and enrich the existing imaging methods.