572PEarly tumour shrinkage (ETS), depth of response (DpR) and associated survival outcomes in patients (pts) with RAS wild type (WT) metastatic colorectal cancer (mCRC) classified according to Köhne prognostic category: Retrospective analysis of the panitumumab (Pmab) PRIME study

Abstract Background Kohne prognostic category classifies mCRC pts as high, medium or low risk. Retrospective analysis of phase 3 trials found that Kohne category predicts survival, pts with BRAF mutant (MT) mCRC represent a separate (higher risk) category, and Pmab-based therapy improves survival vs chemotherapy alone in all four risk groups. We evaluated whether higher Kohne category and BRAF status predicts worse ETS and DpR, and assessed outcomes by ETS ≥30% vs  Methods Retrospective analysis of RAS WT mCRC pts from the phase 3 PRIME study. ETS (% reduction in the sum of the longest diameters of measurable lesions at week 8) and DpR (maximum % change from baseline to nadir [shrinkage]; % change at progressive disease [no shrinkage]) were analysed according to Kohne category. DpR groups: Table . 572P Median PFS and OS by ETS ≥30% vs  ETS 1 , 2 High (n = 74) Medium (n = 236) Low (n = 80) BRAF MT (n = 46) Median PFS, months ≥30% 13.9 12.8 15.4 5.6 6.1 8.9 9.2 5.8 Median OS, months ≥30% 24.6 32.5 40.7 9.6 11.7 19.3 23.6 10.4 DpR 3 High (n = 80) Medium (n = 242) Low (n = 86) BRAF MT (n = 48) Median PFS, months 2.4 2.0 4.0 2.1 0–30% 5.0 5.4 5.4 6.0 31–52% 10.2 10.6 8.5 5.6 53–70% 13.7 11.5 9.9 14.9 71–100% 22.4 17.3 17.7 10.4 Median OS, months 5.5 7.5 10.7 6.4 0–30% 9.4 14.3 13.6 10.9 31–52% 13.8 23.6 20.0 9.4 53–70% 23.1 30.9 28.4 39.5 71–100% 33.2 62.1 47.4 21.4 1 Number of patients evaluable for ETS and DpR differ as patients with disease progression or death before week 8 did not have ETS data available;. 2 For ETS ≥30%: n = 128 (P+F), n = 83 (F); ETS 3 For DpR Results 436 pts receiving treatment (FOLFOX±Pmab) were analysed for ETS, 456 for DpR. The % pts in low-, medium-, high-risk and BRAF MT groups, respectively, achieving ETS ≥30% was 63.8%, 50.4%, 41.9% and 21.7%, and DpR 71–100% was 47.7%, 23.6%, 10.0% and 4.2%. Pts with ETS ≥30% vs  Conclusions Higher-risk categories predict worse ETS and DpR in pts with RAS WT mCRC. Irrespective of risk category, pts achieving ETS ≥30% vs  Clinical trial identification NCT00364013. Editorial acknowledgement David Cutler, PhD, CMPP of Aspire Scientific (Bollington, UK) and funded by Amgen (Europe) GmbH (Rotkreuz, Switzerland). Legal entity responsible for the study Amgen (Europe) GmbH. Funding Amgen (Europe) GmbH. Disclosure A. Sartore-Bianchi: Honoraria (self), Advisory / Consultancy: Amgen; Honoraria (self), Advisory / Consultancy: Bayer; Honoraria (self), Advisory / Consultancy: Lilly; Honoraria (self), Advisory / Consultancy: Sanofi. M. Peeters: Honoraria (self), Research grant / Funding (self), Research grant / Funding (institution): Amgen; Honoraria (self), Research grant / Funding (self), Research grant / Funding (institution): Roche; Honoraria (self): Lilly; Honoraria (self): Merck Serono; Honoraria (self): Remedus; Honoraria (self): Sanofi-Aventis; Honoraria (self): Servier; Honoraria (self): Sirtex; Honoraria (self): Terumo. M. Geissler: Advisory / Consultancy, Research grant / Funding (self), Research grant / Funding (institution): Amgen; Advisory / Consultancy, Research grant / Funding (self), Research grant / Funding (institution): Bayer; Advisory / Consultancy, Research grant / Funding (self), Research grant / Funding (institution): Merck; Advisory / Consultancy, Research grant / Funding (self), Research grant / Funding (institution): Roche; Advisory / Consultancy, Research grant / Funding (self), Research grant / Funding (institution): Sanofi. J. Taieb: Honoraria (self), Advisory / Consultancy: Amgen; Honoraria (self), Advisory / Consultancy: Celgene; Honoraria (self), Advisory / Consultancy: Lilly; Honoraria (self), Advisory / Consultancy: Merck; Honoraria (self), Advisory / Consultancy: MSD; Honoraria (self), Advisory / Consultancy: Roche; Honoraria (self), Advisory / Consultancy: Sanofi; Honoraria (self), Advisory / Consultancy: Servier; Honoraria (self), Advisory / Consultancy: Sirtex. P. Garcia-Alfonso: Honoraria (self), Advisory / Consultancy: Amgen; Honoraria (self), Advisory / Consultancy: Merck; Honoraria (self), Advisory / Consultancy: Roche; Honoraria (self), Advisory / Consultancy: Sanofi; Honoraria (self), Advisory / Consultancy: Servier. T. Price: Advisory / Consultancy, Travel / Accommodation / Expenses: Amgen; Advisory / Consultancy: Merck Serono; Advisory / Consultancy: Roche. P. Burdon: Shareholder / Stockholder / Stock options, Full / Part-time employment: Amgen (Europe) GmbH. Y. Zhang: Shareholder / Stockholder / Stock options, Full / Part-time employment: Amgen Inc. C. Koehne: Honoraria (self): Amgen; Honoraria (self): Bayer; Honoraria (self): Merck; Honoraria (self): Pfizer; Honoraria (self): Servier.