Preoperative IMRT With Concurrent High-dose Vitamin C and mFOLFOX6 in Locally Advanced Rectal Cancer

Inclusion Criteria: 1. 18 to 75 years of age with a confirmed histopathologic diagnosis of adenocarcinoma of the rectum and considered suitable for curative resection. 2. Tumors were clinically confirmed (by MRI or CT plus endorectal ultrasound) as stage II (cT3-4N0) or stage III (cT1-4N1-2), with a positive node defined as ≥1.0 cm in diameter on imaging) and a distal border located , 12 cm from the anal verge. 3. Patients were required to have an Eastern Cooperative Oncology Group performance status ≤ 1 and adequate hematologic, liver, and renal function. (HGB≥90g/L, WBC≥3.5×10\^9/L, PLT≥90×10\^9/L；ALT / AST≤2.5× ULN；T BILL≤1.5×ULN，Cr ≤1.5×ULN) 4. Laboratory examination showed that glucose-6-phosphate dehydrogenase (G6PD) was normal. 5. The patient agreed and had signed the informed consent Exclusion Criteria: 1. With metastatic disease. 2. Prior radiotherapy or chemotherapy. 3. The presence of other cancers. 4. Clinically significant cardiac disease. 5. Known peripheral neuropathy. 6. With intestinal obstruction, intestinal perforation or tumor bleeding who need emergency operation. 7. Rectal cancer with signet-ring cell carcinoma, or with Neuroendocrine tumor.