PANERB study: Panitumumab after cetuximab-based regimen failure.

Abstract

e14000 Background: Metastatic colorectal cancer management (MRCC) has been clearly improved by targeted therapies such as anti-HER1 drugs. The evaluation of the use of targeted therapies in the real world is strategic to assess health politics. OMIT Bretagne-Pays de Loire is a network of private and public cancer centers. Cohorts of patients concerning Folfiri Bevacizumab treatment (Metges et al, ASCO GI 2009), cost of targeted therapies (Grudé et al, ASCO GI 2009) and AvastErb study (Metges et al, ESMO 2009) have been previously published in this topic. Panitumumab and cetuximab can be used in MRCC but no series of patients is available to evaluate the use of panitumumab monotherapy (PM) after cetuximab irinotecan based regimen (CIBR) failure. Methods: The aim of this study is to assess the succession of cetuximab and then panitumumab regimens in a homogenous series of kras wild-type unresectable MRCC. Sex, age, localization of the primary, successive chemotherapeutic regimens, toxicities, response rate, progression free survival and overall survival have been studied. Results: 32 patients (22 men, 10 women, median age 62 years [43–82]) have been prospectively recruted. All of them have received cetuximab associated with Irinotecan and after progression, monotherapy of panitumumab. The primary was colon (59%), rectum (38%) and double sites (3%). Patients received three to nine successive different lines for MRCC. Manageable toxicities for PM were observed especially acnea. Objective response was obtained in 34.4% with CIBR and in 21.9% with PM. Stable disease was obtained respectively in 15.6% and 9.4% with cetuximab and panitumumab regimens. 54.5% patients with objective response to CIBR have been shown to have objective response to PM too and 18.2% are stable (clinical benefit 72.7%). In case of cetuximab resistance, only 7.7% of patients have an objective response and 7.7% are stable (clinical benefit: 15.4%). PFS for CIBR is 3.5 months. PFS for PM is 3.6 months. Overall survival and PFS curves will be shown during the meeting. Conclusions: Our study shows clearly that patients with progression after response with cetuximab regimen have a real opportunity of clinical benefit (72.7%) with panitumumab monotherapy with a high response rate (54.5%). No significant financial relationships to disclose.