演題番号 : IS7-3
Objective: Early tumor shrinkage (ETS) and depth of response (DoR) have been reported to be predictors of better outcomes of the 1st line therapy with anti-EGFR antibody for KRAS-wild type metastatic colorectal cancer (mCRC). We investigate impact of ETS and DoR on survival in the phase II study (PaFF-J study).
Methods: Patients with no prior chemotherapy for KRAS wild type mCRC were arbitrarily received either FOLFOX+panitumumab (Pmab) or FOLFIRI+Pmab. Patients were evaluated every 8 weeks until progression. The sum of the longest diameters of target lesions was used for evaluation. ETS was defined as the radiologic tumor size decrease at the first evaluation (8+2 week). DoR was defined as the maximum decrease rate in size.
Results: Of 162 patients included in full-analysis set (140 with FOLFOX+Pmab and 22 with FOLFIRI+Pmab), 127 and 144 patients with adequate radiologic evaluation and follow-up period were used for ETS and DoR analysis, respectively.
ETS>20% was observed in 98 patients (77.2%); more frequent in the FOLFOX+Pmab group than in the FOLFIRI+Pmab group (89 patients, 80.2% vs. 9 patients, 56.3%). While progression-free survival (PFS) was similar between ETS>20% and ETS<20% group (7.1 vs. 5.1 months, HR 0.66, 95%CI 0.38-1.15, p=0.140), overall survival (OS) was better in ETS>20% group than in ETS<20% group (34.3 vs. 25.9 months, HR 0.55, 95%CI 0.32-0.96, p=0.034).
The median of DoR was similar between the FOLFOX+Pmab and FOLFIRI+Pmab group (53.0% vas. 48.1%), while the median PFS and OS of patients with DoR>upper tertile was better than those with DoR<lower tertile (PFS; 12.0 vs. 2.7 months, HR 0.17, 95%CI 0.09-0.31, p<0.001, OS; 39.1 vs. 28.2 months, HR 0.43, 95%CI 0.23-0.81, p=0.008).
Any clinicopathological characteristic of favorable ETS and/or DoR was not identified.
Conclusions: As same as previously reported by the pivotal Western studies, ETS and DoR correlated to survival of the 1st line therapy with Pmab for KRAS-wild type mCRC.