572P - Panerb Study: Which Category of Patients, Suffering from Metastatic Colorectal Cancer, Can Benefit From Panitumumab Treatment After Cetuximab-Based Regimen Failure?

Abstract

ABSTRACT Background Metastatic colorectal cancer (mCRC) management has been clearly improved by targeted therapies such as anti-HER1 drugs (panitumumab and cetuximab). As evaluation of their use sequentially after progression in the real world is strategic to assess health poliltics, no series of patients is currently available. The Observatory of cancer Bretagne-Pays de la Loire is a network of 50 private and public cancer centers particularly focused on good practise for cancer drugs use. Methods The aim of the study is to evaluate the use of Panitumumab Monotherapy (PM) after previous treatment with Cetuximab-Based Regimen (CBR) in an homogeneous series of kras wild type unresectable mCRC according to EMA approval. Sex, age, localization of the tumor, successive chemotherapeutic regimens, toxicities, response rate, progression free survival (PFS) and overall survival (OS) have been studied. Results 106 patients (73 men, median age 64.4 years [36-86]) previously treated with CBR received PM at progression. The primary tumor site was colon (62%), rectum (35%) and both of them (3%). Patients received successively 1 to 9 lines of treatment for mCRC. Objective responses (OR) were observed in 46% of the patients under CBR and 17% responded again to PM. Disease stabilization was achieved in 17% of the patients treated with CBR and in 13% of the patients treated with PM. Amongst the patients who had an OR with CBR, 31% also had an OR with PM and 16% were stabilized with PM (clinical benefit 47%). In case of cetuximab resistance, only 14% of the patients had a clinical benefit with PM. The median PFS under CBR was 6.6 months IC95% [5.3-7.7] and 3.2 months IC95% [2.8 -3.5] under PM after CBR. The median OS for the patients who achieved a response with both targeted therapies was 25.4 months IC 95% [22.4-42.6] vs 15.0 months IC 95% [12.9-18.3] for the patients who did not (p Conclusion Our study clearly showed that patients with progression after response to cetuximab regimen had a potential opportunity of clinical benefit (47%) with panitumumab monotherapy with a good response rate. OS was potentially increased in responders to the successive use of both targeted therapies. Disclosure J. Metges: conference for Amgen, MerckSerono and Amgen. O. Dupuis: participation in a scientific evening as moderator account for MerckSerono. M. Ferec: participation paid to a board VIFOR invitations congress by Roche, Amgen. J. Douillard: AMGEN : participation in advisory boards and steering committees, speaker in symposia, compensated MERCKSERONO: Research Funding, participation in advisory boards and steering committees, speaker in symposia, compensated. All other authors have declared no conflicts of interest.