comparison of the pathological effect between 2 and 4 cycles neoadjuvant capox for low/intermediate risk ii/iii rectal cancer

Conditions: Rectal Cancer; Neoadjuvant Chemotherapy

Summary: to compare the pathological effect between 2 cycles and 4 cycles of capox regimen as neoadjuvant chemotherapy for low/ intermediate risk stage ii/iii rectal cancer.

neoadjuvant chemotherapy alone has showed much benefit for low/ intermediate risk stage ii/iii rectal cancer which would be verified by the prospect trial. however, the effect of the neoadjuvant chemotherapy was heterogeneous in different patients. it's important to verify those chemo-resistant cases as early as possible. so that, this trial will compare the pathological effect between 2 cycles and 4 cycles of capox regimen as neoadjuvant chemotherapy for low/ intermediate risk stage ii/iii rectal cancer to explore whether those chemotherapeutic non-responders after 2 cycles capox was non-inferior to those after 4 cycles chemotherapy.

Eligibility criteria:
inclusion criteria: 1. age: 18-75 years old; no gender limitation; 2. patients diagnosed with low/intermediate risk stage ii/iii rectal cancer under mri and transanal ultrasound,defined as: low:t3a-bn0-1m0, emvi (±), mrf (-) (≥2mm); middle-high rectal cancer: t3a-cn0-1m0, emvi (±), mrf (-) (≥2mm); no more than 3 lymph nodes with short diameter over 8mm or highly suspected metastases; patients with very low rectal cancer who met the above criteria and could achieve negative circumferential resection margin under elape surgery could be included in the group 3. tumor located \<=12cm from anal verge by colonoscopy or anal examination 4. no distant metastasis confirmed by ct examination; 5. rectal adenocarcinoma confirmed by pathology, 6. ecog score: 0-1; 7. patients with primary rectal cancer who did not receive surgery (except palliative stomy), radiotherapy, systemic chemotherapy or other anti-tumor therapy before enrollment; 8. main organs function normally, that is, meet the following characteristics: ① blood routine examination criteria should meet: hb ≥9g/dl, wbc ≥ 3.5/4.0×109/l, neutrophils ≥ 1.5×109/l, plt≥ 100×109/l. ② biochemical tests should meet the following criteria: crea and bil ≤ 1.0 times upper limit of normal (uln), alt and ast≤ 2.5 times upper limit of normal (uln), alkaline phosphatase (alp) ≤2.5×unl, total bilirubin (tbil) ≤1.5×unl. 9. no history of allergy to platinum drugs when no 5-fu drugs are allergic; 10. women of childbearing age must have had a pregnancy test (serum or urine) 7 days prior to enrolment, be negative, and be willing to use an appropriate method of contraception during the trial and 8 weeks after the last dosing. for men, surgical sterilization or consent to use an appropriate method of contraception during the trial or for 8 weeks after the last dosing; 11. subjects volunteered to participate in this study, signed the informed consent, and showed good compliance and followed up. exclusion criteria: 1. patients suspect to lynch syndrome; 2. patients showed distant metastasis during treatment; 3. previously or coexisting malignancies (including concurrent colon cancer), except for cured basal cell carcinoma of the skin and carcinoma in situ of the cervix; 4. pregnant or breastfeeding women; 5. patients with severe cardiovascular diseases and diabetes that is not easily controlled; 6. people with mental disorders; 7. severe infection; 8. sever renal disfunction; 9. history of gastrointestinal fistula, perforation, bleeding, or severe ulcer; 10. allergic to 5-fu or platinum; 11. the presence of serious gastrointestinal diseases that affect the absorption of oral chemotherapeutic drugs; (12) participants in additional clinical trials within 4 weeks prior to the start of treatment.