Neoadjuvant Bevacizumab + Chemotherapy Combined With Short-course Radiotherapy

Inclusion Criteria:

1. A biopsy proven histological diagnosis of rectal adenocarcinoma；
2. An ARMS-PCR proven KRAS, NRAS mutation, excluding BRAF mutation or microsatellite instablility-High;
3. No intestinal obstruction, distant metastasis was excluded by CT, MRI or PET / CT;
4. MRI proven T3c-T4, CRM positive, N2, extramural vascular invasion positive or lateral lymph node positive of locally advanced rectal cancer;
5. Age between 18-75 years;
6. ECOG (Eastern US Cooperative Oncology Group) score: 0-1;
7. Has sufficient organ function:

   * Hemopoietic function: hemoglobin ≥ 90 g / L, platelet ≥ 80 g / L × 109 / L,
   * neutrophils ≥ 1.5 × 109/L
   * Liver function: ALT and AST \< 2.5 × ULN;
   * Renal function: serum creatinine \< 1.5 ULN;
8. Willing to participate and informed consent signed；

Exclusion Criteria:

1. An ARMS-PCR proven RAS wild type, BRAF mutation and microsatellite instablility-High;
2. Patients having undergone chemotherapy, radiotherapy or surgery for colorectal cancer;
3. Patients with other uncontrolled malignant tumors (except early-stage basal cell carcinoma or cervical carcinoma in situ) ;
4. Female patients who are pregnant or breastfeeding;
5. Patients with severe heart, liver, or kidney, or neurological or psychiatric disease;
6. Patients with active infection;
7. Poor overall health status, ECOG ≥ 2;
8. Patients with concomitant diseases that seriously endanger the safety of patients or affect the completion of the study in the judgment of the investigator;
9. Known hypersensitivity reactions to any investigational drugs;