P1-082 - RAS mutations testing and choice of first-line treatment for metastatic colorectal cancer patients in our institute

Abstract

RAS (KRAS/NRAS) mutations testing other than KRAS exon2 for metastatic colorectal cancer (mCRC) patients(pts) come to be covered by health insurance in Japan from April 2015. RAS mutations testing is enable to select mCRC patients who Anti-epidermal factor receptor (EGFR) antibody therapy may be in terms of survival benefit. A total of 47 colorectal cancer pts were tested RAS mutations in our institute from April 2015 to December 2016. We retrospectively analyzed 32 of 47 pts who were newly diagnosed mCRC and received first-line treatment from April 2015. RAS mutations testing of 32 mCRC pts were 15 RAS wild-type(wt) and 17 RAS mutant type(mt) (KRAS exon2 mt: other RAS mt 11:6). The proportion of Rigt side tumor location(cecum- transverse colon) was more in RAS mt(35.3%) than in RAS wt(20.0%).Medical condition of 32 pts was 'fit'condition of 27 pts (RAS wt:mt 14:13) and 'may be unfit'condition of 5 pts (RAS wt:mt 1:4).Among 14 RAS wt and 'fit'condition pts, 7 pts who assign treatment goal to Cytoreduction were chosen Chemothrapy (CT) doublet plus anti-EGFR and 7 pts who assign treatment goal to Disease control were chosen CT doublet plus Bevacizumab(Bmab) as first-line CT. 13 RAS mt and 'fit'condition pts were all chosen CT doublet plus Bmab as first-line CT. Among 5 'may be unfit'condition pts, 3 pts were chosen reduced CT doublet, 1 pts fluoropyrmidine(FP)+Bmab and 1 pts FP as first-line CT. Regarding first Response Rate evaluation of First-line CT(except discontinued and not evaluated pts), RAS wt and 'fit'condition group was 66.7%, RAS mt and 'fit'condition group was 44.4%,and 'may be unfit'condition group was 25.0%. By undergoing first-lineCT, 4 'fit'condition pts who assign treatment goal to Cytoreduction became possible for Conversion surgery(RAS wt:mt 3:1). We made a choice of first-line treatment for mCRC pts while considering Tumor, Patient, and Treatment characteristics.