The purpose of this study is to evaluate whether injection of carbon nanoparticle as a lymph node tracer before neoadjuvant radiochemotherapy in rectal cancer can increase lymph node yield after surgery compared which do not inject.

This is the randomized controlled, multi-centers，and open-labeled study. The lymph node yield was significantly decreased in rectal cancer after neoadjuvant radiochemotherapy (NAT), hard for pathologists to detect, and is difficult to meet the guideline that minimun of 12 lymph nodes should be retrived after surgery in colorectal cancer. Carbon nanoparticle (CNP) is a specific lymph node tracer, which only dyeing the lymph node, and can keep the lymph node in dyeing state in at least half year. The inverstigator attempted to compare the amount of lymph node yield after surgery in locally advanced rectal caner between injection CNP before NAT and no injection CNP before NAT. In this study, the participants with clinical TNM stage T3+ or N+ will be recruited. The participants will be randomized (1:1 ratio) to a control and intervention arm. The participants in the control arm will not receive injection of any kind lymph node tracers. The participants in the intervention arm will receive injection of CNP before NAT. And the specimen would be evaluated by the pathologist.

Inclusion Criteria:

1. Age: 18-75 years old;
2. Histologically confirmed adenocarcinoma;
3. The rectal adenocarcinoma 0-12cm from the anal margin;
4. Clinical TNM stage: T3+ or N+;
5. Untreated patients (who have not received treatment including radiotherapy, chemotherapy, and surgery);
6. Good liver and kidney function, without contraindications for radiotherapy, chemotherapy or surgery;
7. Able and willing to give informed consent to participate;

Exclusion Criteria:

1. Malignant tumor history or other malignant tumors;
2. Emergency operations such as intestinal obstruction, perforation and hemorrhage;
3. Pregnant or lactating women;
4. History of severe mental illness;
5. Contraindications for radiotherapy, chemotherapy and surgery;
6. Conditions that the researcher thinks it is not suitable for selection.

We need to discuss with other centers, then decide whether to share IPD

Open label