TRUS-FNA For The Prediction Of pCR After Neoadjuvant Treatment In Rectal Cancer

Colorectal cancer is one of the most malignancies worldwide. The dominant clinical research strategy of LARC includes neoadjuvant chemoradiotherapy before radical surgery followed combined with adjuvant treatment. Approximately 15% to 20% of the patients after nCRT can achieve a pathologic complete response (pCR)---no residual tumor is reported at histology after a standard resection. Some researchers suggest that those patients with pCR can be spared the morbidities of surgery instead by a nonoperative approach---watch- and-wait(W\&W). However, neither FDG-PET, MRI, CT, nor enteroscopy can accurately determine a pCR. EUS-FNA has been an important technique for the diagnosis of rectal cancer for its high accuracy and little harm. However, data on the TRUS-FNA for the cytologic diagnosis of pCR in rectal cancer is scarce. Our hypothesis is that adding transrectal ultrasound-guided fine needle aspiration (TRUS-FNA) compared with enteroscopy , MR, and CT alone can improve the accuracy of predicting pCR after nCRT.Therefore, the aim of the study is to assess the performance characteristics of EUS-FNA in this setting.