Inclusion Criteria:

• Age: 18 - 80
• Biooptical confirmed adenocarcinoma of the lower und middle rectum (lower edge of the tumor located max. 14 cm of the anal verge)
• According to MRI tumor extensions into the perirectal fat tissue (cT3)
• No former chemotherapy, radiotherapy and/or tumor resection of a rectum carcinoma
• WHO performance status 0 - 2
• Adequate bone marrow reserve (leucocytes - not more than 3.000/ml; thrombocytes - not more than 100.000/ml)
• Adequate hepatic function (bilirubin - not more than 1.5 x ULN; GOT and GPT - not more than 3.5 x ULN)
• Adequate renal function (creatinin - not more than 1.5 mg/dl)
• Women of childbearing potential: exclusion of pregnancy (negative urin or serum pregnancy test)
• Willingness of women of childbearing potential and accordingly of potent men to use approved contraceptives (for example birth-control pill, loop, condom) during and at least 3 month after closure of the study
• Life expectancy of at least 3 month
• Signed written Informed Consent before recruitment
• Exclusion of distant metastases at the time of recruitment

Exclusion Criteria:

• Former radio- and/or chemotherapy
• Tumor of the upper rectum
• Any other kind of malign tumor in the last five years (except adequate treated basal cell carcinoma of the skin, or in situ cervical carcinoma)
• Peripheral Neuropathy (NCI CTC - not higher than Grade 1)
• General contraindication or hypersensitivity against Oxaliplatin and/or Capecitabine
• Any other untreated not malign diseases: Cardiac insufficiency, angina pectoris, hypertension or arrhythmia, hepatic diseases, significant neurological or psychiatric disorders
• Florid, serious infection at the time of recruitment
• Legally limited capacity or evidence of a neurological or psychiatric disease, the investigator is the opinion it will constrict the patients compliance
• Evidence of lacking willingness for cooperation of the patient
• Pregnant or breast feeding women