Optical Biopsy for Distal Margin in Low Rectal Cancer

This is a multi-center prospective randomized controlled study. In this study, the investigators will use confocal laser endomicroscopy to make real-time in vivo optical biopsy of distal margin in rectal cancer surgery and help surgeons to make surgical decision.The investigators also assess the accuracy of CLE optical biopsy, compared with intra-operative frozen section.

In low rectal cancer surgery, how to select the precise dissection plane and optimal surgical procedure is an important challenge for surgeons. In current clinic, surgeons select dissection plane by a comprehensive judgment of pre-operative pelvis MRI, colonoscopy and digital rectal examination, then through submitting the "doughnut" after cutting and anastomosis to intra-operative frozen section (IFS) to definite whether there is residual tumor in distal margin (DM). However, IFS can only make diagnosis using the tissue specimen in vitro and time-consuming. Once the IFS confirm positive margin, it always means anal resection should be implemented to ensure radical treatment. Therefore, if there is a real-time in situ examination method to evaluate DM in vivo, it will bring great benefits to both surgeons and patients. Confocal laser endomicroscopy (CLE) had been widely used in medical field to diagnose colorectal disease, but it is seldom applied in surgical filed especially in rectal cancer to make optical biopsy and help surgical decision-making. Therefore, the investigators hypothesize that CLE can real-time in situ evaluate DM during surgery in rectal cancer and its accuracy is non-inferior to intra-operative frozen section. In this study, the investigators will randomly assign patients to the experimental group (CLE optical biopsy) and control group (IFS). Using H-E staining pathological diagnosis as golden standard, the accuracy, sensitivity and specificity of both CLE optical biopsy and IFS will be evaluated and compared. And the investigators will also evaluate patients' postoperative urinary function, defection function and quality of life through a year follow-up.