Background: It is still a topic of ongoing debate as to which of the two agents, anti-VEGF antibody or anti-EGFR antibody, is more effective in patients with KRAS Exon 2 or RAS wild-type metastatic colorectal cancer (mCRC) in the first-line setting. ATOM is a multicenter, randomized trial comparing mFOLFOX6 plus bevacizumab (Bmab arm) with mFOLFOX6 plus cetuximab (Cmab arm) in patients with liver-limited metastases unsuitable for upfront resection. Methods: Patients with previously untreated mCRC were eligible if they had ≥5 liver-limited metastatic lesions and/or had liver-limited metastases with the maximum lesion diameter of > 5cm. Patients with KRAS Exon2-wild were registered but after Jan 2015 limited to those with all RAS-wild. Primary endpoint was progression-free survival (PFS), which was defined as the time from randomization to disease progression, recurrence after resection by surgery, or death from any cause (Central review). Key secondary endpoints included overall response rate (ORR), liver resection rate, and overall survival (OS). Results: A total of 122 pts were enrolled between May 2013 and April 2016. Of 116 eligible (59 in the Cmab arm and 57 in the Bmab arm), median age was 65/64 in the Cmab/Bmab arm; ECOG PS 0, 86/89%; all RAS wt, 98/95%; left-sided primary tumor, 76/84%. Efficacy results were summarized in the table. With a median follow-up of 24.3 months, the median PFS was 15.0 months in Cmab arm and 11.6 months in the Bmab arm with a hazard ratio of 0.803 (95%CI, 0.513–1.256), whereas ORR was 86% in the Cmab arm and 68% in the Bmab arm. Liver resection rate was 49% and 56% in the Cmab arm and the Bmab arm, respectively. Conclusions: In patients considered unsuitable for upfront resection of liver-limited metastasis, the two agents showed a similar efficacy. OS result will be presented elsewhere. Clinical trial information: NCT01836653