Value of endorectal ultrasonography in the assessment of invasion staging of low rectal cancer with local progression after neoadjuvant radiochemotherapy.

Although stages T3 and T4 rectal cancer can be reduced to T1 or T2 after neoadjuvant radiochemotherapy, the accuracy of the en-dorectal ultrasonography (ERUS) for the post-radiochemotherapy evalua-tion of low rectal cancer has seldom been reported. We aimed to investigate the value of ERUS in the assessment of invasion staging in low rectal cancer with local progression, and the factors affecting its accuracy, after neoad-juvant radiochemotherapy. A total of 114 patients administered with neo-adjuvant radiochemotherapy for stages II and III low rectal cancer (local stage T3/T4) from February 2018 to December 2020 were enrolled in the study. The changes in local lesions were evaluated using ERUS before and after radiochemotherapy, and compared with the pathological T staging. The accuracy of post-neoadjuvant radiochemotherapy re-staging examined with ERUS was evaluated, and univariate analysis was used to identify the factors affecting the accuracy. After neoadjuvant radiochemotherapy, the blood flow distribution within the lesion significantly declined (P<0.05), the max length and max thickness of the longitudinal axis of the lesion were reduced (P<0.05), and the uT staging was decreased (P<0.05), when compared with lesions before the treatment. Compared with postoperative pathological T staging, the accuracies of ERUS in T1, T2, T3 and T4 stages were 11.11%, 28.57%, 27.27% and 100%, respectively. Univariate analysis indicated that review time of ERUS, post-operative T staging and Wheeler rectal regression stage were factors affecting the accuracy of ERUS re-stag-ing. ERUS is more accurate for T4 re-staging, follow-up reviewed six weeks after neoadjuvant radiochemotherapy and low regression tumors, with a high application value for the assessment of the efficacy of neoadjuvant radiochemotherapy for low rectal cancer.