Efficacy of FOLFIRI-3 (irinotecan D1,D3 combined with LV5-FU) or other irinotecan-based regimens in oxaliplatin-pretreated metastatic colorectal cancer in the GERCOR OPTIMOX1 study

Background: Second-line irinotecan-based chemotherapy is commonly used in metastatic colorectal cancers after first-line oxaliplatin-based chemotherapy. No standard schedule of irinotecan has been established in this situation. Patients and methods: Metastatic colorectal cancer patients included in the OPTIMOX1 phase III study received first-line oxaliplatin-based chemotherapy (FOLFOX). No second line was defined in the protocol, but data concerning second line were prospectively registered. Inclusion criterion was patients receiving an irinotecan-based second-line chemotherapy. Second-line progression-free survival (PFS) and tumor response were evaluated according to type of irinotecan-based regimen administered. Results: A total of 342 patients received irinotecan-based chemotherapy as second-line chemotherapy: FOLFIRI-3 [n = 109, irinotecan 100 mg/m(2) days 1 and 3 combined with leucovorin (LV) 400 mg/m(2) day 1 and 46-h continuous 5-fluorouracil (5-FU) 2000 mg/m(2)], FOLFIRI-1 (n = 112, irinotecan 180 mg/m(2) day 1 combined with LV 400 mg/m(2) day 1, 5-FU bolus 400 mg/m(2) and 46-h continuous 5-FU 2400 mg/m(2)) and other various irinotecan-based regimens (n = 121). Median second-line PFS was 3.0 months (FOLFIRI-3: 3.7 months; FOLFIRI-1: 3.0 months; other regimens: 2.3 months). In multivariate analysis, FOLFIRI-3 regimen (relative risk 0.43, 95% confidence interval 0.28-0.68, P = 0.0003) and lactate deshydrogenase level at inclusion (P = 0.0006) in OPTIMOX1 were associated with a longer second-line PFS. Conclusion: In unselected patients pretreated with oxaliplatin, PFS in second line appeared to be improved by FOLFIRI-3 regimen.