Therapeutic effect of TAS-102 (A) in patients (pts) with metastatic colorectal cancer (mCRC) refractory to standard chemotherapy by the Köhne model (Km).

Abstract

650 Background: TAS-102 is a novel oral antitumor agent consisting of trifluorothymidine and thymidine phosphorylase inhibitor. In the TAS-102 phase II study, TAS-102 significantly improved overall survival (OS) compared with placebo (P) in pts with mCRC who had 2 or more prior regimens and refractory to fluoropyrimidine, irinotecan and oxaliplatin (A: 112pts; P: 57 pts; median OS, 9.0 vs 6.6 months (M); HR, 0.56; p = 0.0011) [K. Yamazaki et al. JSMO 2011 Abst 10428, Y. Kuboki et al. ECCO 2011 Abst 6005]. Km [Ann Oncol 2002; 13:308-317] suggested predictive prognosis marker and showed 4 parameters to classify pts with mCRC treated 5-FU-based first line chemotherapy into 3 risk groups (low risk group (L), intermediate risk group (IM) and high risk group (H)). We retrospectively evaluated TAS-102 phase II study by Km. Methods: Classification of pts into each risk group was done as follows: L is ECOG performance status (PS) 0-1, 1 tumor site; IM is (1) PS 0-1, >1 tumor site, ALP <300 IU/L and (2) PS >1, WBC <10×109 /L, 1 tumor site; H is (1) PS 0-1, >1 tumor site, ALP ≥300 IU/L, (2) PS >1, WBC <10×109 /L, >1 tumor site and (3) PS >1, WBC ≥10×109 /L. Progression-free survival (PFS) was assessed by an independent review committee. Results: Pts were classified as L/ IM/ H in 36/ 31/ 102 pts. The median OS for TAS-102 vs Placebo were in L (not reached vs 10.1M; hazard ratio (HR), 0.62), in IM (9.0 vs 4.9 M; HR, 0.44) and in H (7.6 vs 5.6 M; HR, 0.58). This risk stratified analysis by Km demonstrated that HR of OS and PFS was similar in each risk group (Table). Conclusions: The OS and PFS of TAS-102 were superior to that of placebo in all risk groups by Km. Further prospective TAS-102 phase III study is necessary to confirm these results. [Table: see text]