This study compares capecitabine with standard 5-FU in the perioperative treatment of locally advanced rectal cancer.

5-Fluorouracil (5-FU) based chemoradiotherapy (CRT) is regarded a standard perioperative treatment in locally advanced rectal cancer (LARC). We investigate the replacement of 5-FU by the oral pro-drug capecitabine (cape) within a randomized phase III trial. Patients aged ≥18 years with LARC stage II or III are recruited into this two-arm, two-cohort randomized non-inferiority phase-III trial (arm A: cape, arm B: 5-FU; cohort [C] I: adjuvant, C II: neoadjuvant). Regimens: Arm A: CRT: 50.4 Gy + cape 1,650 mg/m² days 1-38 plus five cycles of cape 2,500 mg/m² d 1-14, repeated d 22 (C I: 2 x cape, CRT, 3 x cape; C II: CRT, TME surgery followed by cape x 5). Arm B: CRT: 50.4 Gy + infusional 5-FU 225 mg/m² daily [C I] or infusional 5-FU 1,000 mg/m² d 1-5 and 29-33 [C II] plus 4 cycles of bolus 5-FU 500mg/m² d 1-5, repeated d 29 (C I: 2 x 5-FU, CRT, 2 x 5-FU; C II: CRT, TME surgery followed by 5-FU x 4). Primary endpoint is 5-year overall survival (OS), secondary endpoints comprise 3-year disease-free survival (DFS) and safety.

The study is designed to investigate whether 5- year overall survival rate (SR5) is non-inferior in arm A versus arm B. We hypothesize that SR5 in the standard arm B is 57.5%. Sample size calculation is performed with a power of 80% and a type I error of 5% and with a drop-out rate of 5%. Therefore, a total of at least 372 evaluable patients (i.e. 186 per arm) is required to confirm non-inferiority of the experimental arm A with a non-inferiority margin of maximal 12.5% and a median follow-up time of 48 months.

Inclusion Criteria:

• Eligible patients are 18 years or older and have histologically confirmed adenocarcinoma of the rectum (defined as the distal border of the tumour less than 16 cm from the anal verge measured by rigid rectoscopy) with no evidence of distant metastases (identified by abdominal ultrasound or CT scan and chest radiography).
• Patients in the adjuvant cohort have undergone R0-resection by total mesorectal excision (TME) of a pT3-4 N any or T any N positive non-metastatic rectal cancer.
• Patients treated in the neoadjuvant cohort need to have a clinical T3-4 N any or T any N positive tumour staged by endoscopic ultrasound, provided the lower border of the tumour is located 0 - 16 cm from the anal verge measured by rigid rectoscopy and the primary tumour is deemed resectable by TME surgery on the basis of clinical assessment. Other eligibility criteria comprise: WHO status of zero or one; adequate liver, renal, and bone marrow function defined as follows: leucocyte count > 3,500/µl, thrombocyte count > 100,000/µl, hemoglobin > 10.0 g/dl; serum bilirubin < 2.0 mg/dl, serum creatinine < 2.0 mg/dl.

Exclusion criteria:

• Prior treatment for rectal cancer, prior chemo- or immunotherapy, prior pelvic radiotherapy, or a history of other malignant diseases within the past five years with the exception of successfully treated basal carcinoma of the skin or carcinoma in situ of the uterine cervix.
• Participation in another trial, pregnancy, breast-feeding, unwillingness to use effective contraception, or a medical condition or concomitant illness which could potentially interfere with compliance to the protocol are regarded as exclusion criteria, as well.