Background: The FIRE-3 study (AIO KRK-0306) was designed as a randomized multicenter trial to compare the efficacy of FOLFIRI plus cetuximab (cet) to FOLFIRI plus bevacizumab (bev) as first-line treatment in KRAS WT mCRC patients. FOLFIRI plus cet as first-line treatment of KRAS WT mCRC patients resulted in comparable overall response rates (ORR) and progression free survival (PFS) when compared to FOLFIRI plus bev. Overall survival (OS) was significantly longer in the FOLFIRI plus cet arm. Methods: In this exploratory analysis outcome parameters were calculated in dependence of progression during antibody treatment. As reported before by Saltz et al. (ASCO GI 2007) an “on study treatment” population was defined using all RAS wild-type pts that were treated until progression or death occurred. To exclude early progressing patients the analysis was also performed in patients with a PFS >6 months. Results: See Table. Conclusions: In general, patients progressing during 1^st-line treatment had a shorter PFS and OS than patients that had progressed after stop of treatment for any cause. Patients that discontinued treatment for other reasons than progression had a significantly longer median OS when treated with FOLFIRI plus cetuximab in first-line when compared to FOLFIRI plus bevacizumab. This effect was also seen after exclusion of early progressors (PFS <6 mo).