BACKGROUND: This study reports the long-term follow-up of patients with metastatic colorectal cancer (CRC) participating in a randomised phase II study that compared the efficacy and toxicity of the combination of irinotecan (IRI), fluorouracil (FU) with leucovorin (LV) (arm A) versus sequential chemotherapy with IRI plus FU/LV followed by oxaliplatin (OXA) plus FU/LV (arm B) as first line therapy.MATERIALS AND METHODS: Intent-to-treat analysis was performed on 417 patients (211 in arm A and 206 in arm B). Treatment schedules of weekly IRI 80 mg/m(2) or OXA 45 mg/m(2) plus LV 200 mg/m(2) immediately followed by intravenous bolus FU 450 mg/m(2) for 6 weeks were followed by a 2-week rest period. Treatment continued for 4 cycles. Patients in arm A were treated with IRI/FU/LV for 4 cycles, while patients in arm B were initially treated with IRI/FU/LV for 2 cycles followed by sequential administration of 2 cycles of OXA/FU/LV.RESULTS: No significant difference emerged in overall response rate or overall survival. There was a difference in progression-free survival (median, 7.3 versus 8.2 months, p=0.040) in favour of arm B. Toxicity profiles were similar in both arms.CONCLUSION: IRI/FU/LV and IRI/FU/LV followed by OXA/FU/LV showed comparable activity with a manageable toxicity profile.