Panitumumab after progression on cetuximab in patients with KRAS wild-TYPE (WT) metastatic colorectal cancer (MCRC): A single institution experience.

e14605 Background: Cetuximab and panitumumab are monoclonal antibodies that target EGFR, approved for the treatment of KRAS WT MCRC. Few data describe the activity of panitumumabafter cetuximab-irinotecan based regimen failure. Methods: The aim of this study is to assess if panitumumab has some activity in pts with KRAS WT MCRC that has progressed on prior cetuximab. Results: We retrospectively analysed 25 pts with KRAS WT MCRC who received from 07/2009 to 01/2013 panitumumab after progression on cetuximab. Median age: 63 yrs (40-78), primary site tumor: colon 64%, rectum 36%; synchronous metastases 36%, metachronous 64%. Sites of metastases: liver 44%, liver and lung 8%, other sites 48%. All pts had previously received cetuximab associated with irinotecan (20 pts) or oxaliplatin (5 pts) and subsequently received panitumumab. We withdrew cetuximab because of intolerance in 4 pts (16%), while 21 pts (84%) with ECOG PS 0-1 who had previously responded to cetuximab (ORR plus SD lasting more than 5 months) re...