511 Background: KRAS p.G13D mutant metastatic colorectal cancer (mCRC) has been identified to represent a cetuximab-sensitive subtype of KRAS mutant mCRC. This analysis aims to answer the question whether first-line treatment of p.G13D mCRCs should contain cetuximab or bevacizumab. Methods: Fifty-four patients with p.G13D mutant mCRC were pooled in this analysis. All patients underwent systemic 1st-line treatment with a fluoropyrimidine and oxaliplatin/irinotecan that was combined with either cetuximab or bevacizumab. Results: Overall response rate was comparable between cetuximab- and bevacizumab-based regimens (58% vs 57%). Progression-free survival was comparable (8.0 months-cetuximab-group vs 8.7 months bevacizumab-group). Overall survival (OS) was longer in patients treated with cetuximab as first-line therapy (20.1 months vs 14.9 months). Logistic regressions modelling OS revealed oxaliplatin-based first-line treatment to correlate significantly with poor outcome (p=0.03). Moreover, a strong trend in favour of capecitabine compared to infusional 5-FU (p=0.06) was seen.. Responders among our cohort showed a benefit concerning PFS and OS undergoing cetuximab- but not bevacizumab-based regimen. Conclusions: This retrospective pooled analysis suggests that cetuximab-based first-line therapy in p.G13D mutant mCRC shows similar activity compared to bevacizumab-containing regimen. Infusional 5-FU and oxaliplatin may represent inferior options compared to capecitabine and irinotecan in p.G13D mutant mCRC 1st-line treatment.