• Matthew Loft, Jeremy Shapiro, Margaret Lee, Rachel Wong, Jeanne Tie, Suzanne Kosmider, Vanessa Wong, Azim Jalali, Belinda Lee, Sumitra S Ananda, and Peter Gibbs.
• Division of Personalised Oncology, Walter and Eliza Hall Institute of Medical Research, Melbourne, Victoria, Australia.
• Intern Med J. 2023 Sep 1; 53 (9): 161016171610-1617.

BackgroundTreatment with cetuximab provides a survival benefit for patients with RAS wild-type metastatic colorectal cancer (mCRC). Practice-defining cetuximab studies utilised weekly (q1w) administration. More convenient second weekly (q2w) administration is supported by pharmacokinetic data and a recent meta-analysis, but large head-to-head studies have not been conducted. Therapeutic Goods Association (TGA) prescribing information states cetuximab be administered q1w for all indications.AimTo assess the real-world use of q1w versus q2w cetuximab schedule and any difference in outcomes.MethodsWe analysed data from a prospective mCRC database at seven Melbourne hospitals from January 2010 to August 2019. Characteristics and outcomes for cetuximab-treated patients were examined, comparing q1w versus q2w schedules. Progression-free survival (PFS) and overall survival (OS) were the primary endpoints.ResultsOf 214 eligible patients, 103 (48%) received q1w and 111 (52%) received q2w cetuximab. Q2w cetuximab has been used in >70% of patients from 2015. Q2w was more commonly used in public patients (70% vs 13% in private, P < 0.001), in left-sided primary tumours (83% vs 68%, P = 0.025) and in combination with chemotherapy (73% q2w vs 40% q1w, P < 0.001). Q2w treatment was less common in BRAFV600E mutated tumours (4% vs 13%, P = 0.001). PFS was similar across all lines of therapy, including when analyses were limited to a left-sided primary and there was no difference in OS in multivariate analysis.ConclusionThis real-world analysis shows q2w cetuximab has become the dominant method of administration, despite TGA guidance. Our outcome data adds to other data supporting the use of q2w cetuximab as the standard option. Consideration could be given to modifying current TGA advice.© 2022 Royal Australasian College of Physicians.

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