545PQUANTITATIVE ANALYSES OF EARLY TUMOR SHRINKAGE ON CLINICAL OUTCOME IN AN OPEN, NON-RANDOMIZED, MULTICENTER PHASE II CLINICAL TRIAL (CLIME STUDY)

ABSTRACT Aim: Early tumor shrinkage (ETS) is associated with long-term outcome in patients receiving chemotherapy plus cetuximab, which was investigated in CRYSTAL and OPUS trials. CLIME study (NCT01322178) was designed to observe whether the addition of targeted drug in first line further increases the curative resection rate and improves long-term survival in KRAS wide-type colorectal liver limited metastases patients in China. This retrospective analysis aims to show the impact of ETS on long-term outcome in CLIME study. Methods: Radiologic assessments at week 8 were used to calculate the relative change in the sum of the longest diameters of the target lesions. A 20% decrease cutoff value was selected as a dichotomization threshold for further investigation. Outcome measures were objective response rate (ORR), curative resection rate and progression-free survival (PFS). Cox regression models were used to quantify individual changes in tumor size over time and to relate these changes to PFS. Results: From the ITT cohort (100 cases), 92 patients were available for ETS assessment and 70 pts achieved ETS (76.1%). These data were comparable with quantitative analysis of ETS in CRYSTAL and OPUS trials (table 1). Longer PFS was observed in patients who achieved ETS as compared to patients with no-ETS (10.9m vs. 6.2m, HR 0.203, 95%CI 0.087-0.473, P CLIME n = 92 CRYSTAL n = 299 OPUS n = 78 ETS rate (%) 70 (76.1%) 184 (62%) 54 (69%) mPFS in ETS group 10.9m 14.1m 11.9m mPFS in no-ETS group 6.2m 7.3m 5.7m HR 0.203 0.32 0.22 P value KRAS exon2 wt only Conclusions: Quantitative analyses from CLIME study further revealed the value of the variable ETS as a potential efficacy outcome measure for KRAS wild-type colorectal liver-limited metastases patient in China. Reference:Piessevaux et al., JCO 2013 Disclosure: All authors have declared no conflicts of interest.