Cetuximab plus Irinotecan versus Panitumumab in Patients with refractory metastatic colorectal cancer in Ontario, Canada

Abstract

The addition of irinotecan to an EGFR antibody has previously been shown to improve tumor response rate and time to progression but not overall survival (OS) for refractory metastatic colorectal cancer (mCRC). We assessed the “real world” effectiveness and toxicity of the combination versus monotherapy.

In Ontario, Canada universal public funding is available for either cetuximab plus irinotecan (Cmab+I) combination therapy or panitumumab (Pmab) monotherapy, only in patients with refractory non-mutated RAS mCRC. All patients diagnosed before December 2012 and treated with an EGFR antibody for mCRC were identified from the Ontario drug database and linked to the Ontario Cancer Registry and other administrative databases to ascertain baseline characteristics, health services utilization and outcomes. Multivariable Cox and logistic models were constructed to compare the time to treatment discontinuation (TTD), OS, emergency department (ED) or hospital visits between Cmab+I and Pmab. Observable confounders were adjusted for using propensity score methods.

1081 patients were identified (Cmab+I: 278, Pmab: 803). Patients receiving Cmab+I were younger (mean age 61 vs. 64 years) and had a longer duration of prior irinotecan treatment. The use of Cmab+I as compared to Pmab alone was associated with a prolonged TTD [median: 3.8 months vs. 2.8 months] and an improved OS [median: 8.8 mos vs. 5.9 mos] with an adjusted HR of 0.62 [95% CI 0.53-0.73, p<0.001]. Both treatment regimens afforded similar 14-day mortality and incidence of ED or hospital visits. The findings for patients over and below the age of 65 were similar. This article is protected by copyright. All rights reserved.

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