The primary objective was to improve adjuvant 5-FU chemoradiotherapy in resectable rectal cancer. The investigators hypothesis was that modulation of 5-FU by addition of either FA or INF-alpha may increase overall survival.

Primary endpoint was overall survival (OS). For sample size estimation the following assumptions were made: The 5-year OS rate of 5-FU was estimated to be 58%. Our intention was to detect an increase in the 5-year OS rate by one of the additives of at least 10% with a power of 80% and a level of significance of 5% in comparison to 5-FU (one-sided). Hypotheses were analyzed as pair wise comparisons between the treatment options. This resulted in a target sample size of 280 patients per group and a total of 840 patients.

Inclusion Criteria:

• Eligibility was defined as potentially curative en-bloc resection (R0) of an adenocarcinoma of the rectum with a lower tumor edge within 12 cm from the anal verge determined by rectoscopy, a pathologic UICC stage II (pT3/4pN0M0) or III (pT1-4pNposM0) with examination of at least 12 lymph nodes, a white blood count ≥ 3,500/µl, a platelet count ≥ 100,000/µl, a ECOG performance status of 0 or 1, and written informed consent.

Exclusion Criteria:

• Ineligible were patients not fulfilling these criteria or having a history of cancer except for adequately treated superficial basal or squamous cell skin cancer or in situ carcinoma of the cervix, getting previous radio- or chemotherapy, pregnant or nursing women, other having severe concomitant diseases limiting life expectancy or not allowing chemotherapy, and with social conditions not allowing a 5-year follow-up.