23 Background: Cetuximab (CET) administered weekly (q1w) at 250 mg/m², after an initial dose of 400 mg/m², is approved in combination with chemotherapy (CT) for the treatment of (K) RAS wild-type metastatic colorectal cancer (mCRC). The use of CET 500 mg/m2 administered with CT every 2 weeks (q2w) is according to US clinical practice guidelines and observed routinely. In this study, we compared q2w vs q1w regimens on overall survival (OS) in a presumed first-line (1L) treatment subcohort and present updated data on the noninferiority of q2w vs q1w in line-agnostic (1L+) treatment using US real-world data. Methods: Using IBM MarketScan, a large US insurance claims database, we classified a cohort of mCRC patients treated between 07/2010 and 12/2016 with CET+CT as q1w or q2w based on observed infusion patterns. Absence of mCRC-related treatment claims preceding CET initiation date (defined as the index date) qualified as CET treated in 1L. A validated algorithm was used to determine patient death. Confounding was accounted for using high-dimensional propensity scoring (hdPS) with inverse probability of treatment weights. OS was compared using Cox proportional hazards regression. Imbalanced confounders after hdPS were added to the Cox model. In 1L+, noninferiority of the q2w regimen was tested with a margin hazard ratio (HR) of 1.25. However, noninferiority could not be tested in 1L due to the small sample size; a test for difference was used instead. Results: Of 2,730 CET-exposed mCRC patients (updated), 1,779 (65.2%) and 951 (34.8%) were classified in q1w and q2w groups, respectively, among which 557 (31.3%) and 316 (33.2%) received CET in 1L. The HR (95% CI) for OS of q2w vs q1w in 1L was 1.10 (0.92-1.31; crude), and 1.05 (0.86-1.29; adjusted; p for difference: 0.625). In 1L+, crude and adjusted HRs were 1.05 (0.94-1.18) and 0.94 (0.85-1.03), respectively, rejecting the inferiority hypothesis at p < 0.001. Conclusions: Only a third of patients received CET in 1L in this study. OS was statistically noninferior in q2w vs q1w in 1L+, and adjusted results in 1L suggest no differences between both treatment schedules. However, more data would be needed to formally test the noninferiority hypothesis in 1L.
4CPS-275 Efficacy and safety of trifluridine/tipiracil in patients with metastatic colorectal cancer: real world data
