568P - BRAF mutated metastatic colorectal cancers do not always possess poor clinical outcome

Abstract

BRAF mutated (mBRAF) metastatic colorectal cancers (mCRC) are known to be related poor prognosis and low response to current chemotherapy. We investigated clinical outcomes of unselected mBRAF mCRC patients (pts) treated in real clinical practice. A total of 125 pts with mBRAF mCRC were treated between Jan 2005 and OCT 2015 at Asan Medical Center. We analyzed clinical outcomes, such as survival and progression free survival after 1st (PFS1), 2nd (PFS2), and 3rd (PFS3) line palliative chemotherapy (pCT), of these pts using mCRC registry data of our center. Out of 125 tumors, 121 had BRAF mutation of V600E; 3 of K6001E; 1 of V600E and K600E. Median age was 59 years old and 70 (56.0%) pts were male. Primary tumor was located in right colon in 60 (48.0%) pts, left colon in 43 (34.4%) pts, and rectum in 22 (17.6%) pts. KRAS exon 2 mutation was tested in all pts; 122 had no mutation, while 3 had co-mutation of KRAS. NRAS mutation was tested in 29 (23.2%) pts and known to be all wild type. Microsatellite instability (MSI) status was assessed in 86 (68.8%) pts; 10 (8.0%) were MSI and 76 (60.8%) were microsatellite stable. Median survival of all pts was 14.6 months (mos). Out of 125 pts, 115, 84, and 37 pts were treated with 1st, 2nd, and 3rd line pCT, respectively. Median PFS1, PFS2 and PFS3 were 5.7, 2.5 and 1.9 mos, respectively. Survival of 12 patients was longer than 30 mos, which is comparable to wild type BRAF mCRC. PFS1 of these patients was longer than others with median 12 cycles of 1st line pCT; 19.5 vs. 5.3 mos. (p < 0.0001). Clinical outcomes of unselected mBRAF mCRC pts treated in real clinical practice were generally similar to previous studies; short survival and PFS. But, 9.6% of pts survived longer than 30 months, which is comparable survival to wild type BRAF mCRC. PFS1 of these pts was also longer than others. Further genetic analysis is warranted to define genetic features of mBRAF tumors with better prognosis.