719P - Tumour Shrinkage at 6 Weeks Predicts Favorable Clinical Outcomes in a Phase III Study of Gemcitabine and Oxaliplatin with or Without Erlotinib for Advanced Biliary Tract Cancer

Abstract

Background: The aim of this study was to determine whether early tumor shrinkage (ETS) at 6 weeks after treatment correlates with progression-free survival (PFS) and overall survival (OS) in advanced biliary tract cancer (BTC) patients receiving gemcitabine plus oxaliplatin (GEMOX), with or without erlotinib. Methods: This was a multicenter, open label, randomized, phase III trial of 103 BTC patients (ClinicalTrials.gov Identifier; NCT01149122, and Rigistration date; January, 7, 2010), comparing GEMOX with GEMOX plus erlotinib. Tumor shrinkage was expressed as a relative decrease compared to baseline and was dichotomized according to a previously reported cutoff value of 10 %. Results: Fifty-four patients (52.4 %) received GEMOX and 49 patients (47.6 %) received GEMOX plus erlotinib. The latter achieved a better overall response rate (RR) (40.8 % vs. 18.6 %, p= 0.02) and showed ETS more frequently (63.2 % vs. 40.7 %, p= 0.03). ETS was significantly correlated with the overall RR (correlation coefficient, 0.53; p< 0.01). The median PFS and OS did not differ according to erlotinib administration. However, the median PFS (7.3 vs. 2.1 months, p< 0.01) and OS (10.7 vs. 5.8 months, p< 0.01) were significantly longer amongst patients with ETS at 6 weeks after treatment, irrespective of erlotinib administration. In patients with wild-type KRAS who were treated with GEMOX plus erlotinib, ETS was a significant prognostic factor for PFS (p< 0.01). Conclusions: ETS might predict PFS and OS in BTC patients treated with GEMOX with or without erlotinib. Additionally, ETS may be an indication for adding erlotinib to chemotherapy for BTC patients wild-type KRAS. These findings need to be prospectively validated.