Background: Cetuximab 250mg/m² weekly (Q1W) after an initial dose of 400mg/m² is approved for treatment of K-Ras wild-type mCRC. In real world 29% of patients received cetuximab 500mg/m² biweekly (Q2W). In this study overall survival (OS) associated with Q2W vs Q1W dosing of cetuximab for mCRC in real world was compared. Methods: This study utilized Flatiron Health electronic health record-derived database to identify adult patients with stage IV or recurrent K-Ras wild-type mCRC who received cetuximab+FOLFIRI/FOLFOX/irinotecan, or cetuximab monotherapy in first, second or third-line therapy from 01/01/2013 to 12/31/2019. Patients were assigned to Q1W or Q2W cohort if they had 70% or more cetuximab infusions with a gap of 4-10 days or 11-18 days from previous infusion. Patients who did not fall into either cohort were excluded from analysis. Propensity score (PS) matching was used to balance cohorts on their baseline demographic, clinical and treatment characteristics. Kaplan-Meier methods and Cox proportional hazards regressions were used to compare OS. Results: Baseline characteristics for Q2W (N = 422) vs Q1W (N = 653) cohorts before PS matching- median age 62 vs 65 years, male 58.5% vs 59.3%, white 68.3% vs 66.5%, stage IV 56.6% vs 58.5%, ECOG PS 0/1 61.6% vs 52.1%, ECOG PS 2+ 9.2% vs 9.5%. After PS matching, baseline characteristics were balanced. Hazard ratios (HRs) comparing OS in PS-matched Q2W vs Q1W cohorts were not significant for overall or line of therapy populations (Table). Conclusions: Weekly and biweekly cetuximab had comparable effectiveness in this real-world study.